July 27th, 2014
A friend of ours recently took delivery of a new barrel which was chambered by a smith who had done the original build on the rifle, but who had not headspaced the barrel on the action itself this time. The smith headspaced based on his old records. Our friend happily screwed on his nice, new barrel and headed to the range. After the first few rounds, with known, safe loads, he was seeing deep craters on his primers, and then he even pierced a few primers with loads that should never have done that. Interestingly, the brass was not showing any of the other pressure signs. This was with bullets seated .015″ out of the rifling.
We were thinking maybe too much firing pin extrusion or maybe he got a hot lot of powder. Then I asked him to email me dimensions off his fired cases compared to new, Lapua brass. He emailed me that his shoulder moved 0.0105″ forward. I sent an email back saying, “hey, that must be a typo, you meant 0.0015″ right–so your shoulder moved one and a half thousandths correct?” The answer was “No, the shoulder moved over TEN thousandths forward”. Ahah. This explained some of the cratering problem in his brass. His cases were able to bounce forward enough in the chamber so that the primer material was smearing over the firing pin. And now he has brass that is “semi-improved”.
The point of the story is always check your headspace when you receive a “pre-fit” barrel, even from the smith who built the rifle. Purchase Go/No Go gauges for all your calibers. Headspace is not just an accuracy issue, it can be a safety issue. Pierced primers are bad news. The debris from the primer cup can blow into the firing pin hole or ejector recess causing a myriad of problems.
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July 21st, 2014
Muzzle brakes are controversial. Some people swear by them, while others swear at them. Still, there’s no question that a good brake can reduce felt recoil up to 45%. And likewise, the best brakes, when installed properly, seem to have no negative effect on accuracy.
Roy Bertalotto has done considerable experimentation with muzzle brakes, testing dozens of brake designs on his own rifles over the past few years. Roy’s article, Adventures with Muzzle Brakes, discusses various aspects of muzzle brake design and performance. Roy doesn’t claim that his testing is definitive, but his article is definitely worth a read. Here are some of Roy’s interesting findings:
Exit Hole Diameter
“Best accuracy and effectiveness of the brake was obtained with a hole .020″ over bullet diameter. If the exit hole is too small, such as +.005″ over bullet diameter, accuracy suffers. If the depth of the exit hole is too shallow, the metal around the hole will erode very quickly.”
“The most effective braking was with a brake 1″ in diameter with a 3/4″ exit hole on each side, just in front of the muzzle. The bullet passes through a cone of 35 degrees before it exits the brake. (Like the tank example), Incredible reduction of recoil. But loud and ugly. Very easy to make since you don’t need a spin fixture or a dividing head.”
Bottom Gas Venting Helps Accuracy
“In my tests, not having holes all around the brake effects accuracy a bit. I believe it does something to the bullet by the air pushed ahead of the bullet creating unequal turbulence in the bullet path. I’ve tried a few brakes where I drilled only holes on the top, test fired, and then completed holes on the bottom and in every case, accuracy improved.” Below are spiral-ported brakes crafted by Clay Spencer.
Brakes Work Best with High-Pressure Cartridges
“The higher the pressure of the particular round, the more effective the brake. I have over 20 rifles with brakes. The 220 Swift is the king of reduction. Followed very closely by the 25-06, 6mm Remington, any Weatherby small bore. With a proper brake and a hot handload under a 40 gr bullet, the Swift will move 1/2″ to the rear and 0 muzzle rise! Big boomers with low pressure like 45-70s and shot guns benefit the least.” [Editor's Note: Roy is judging effectiveness by the percentage of recoil reduction rather than absolute levels of recoil. Obviously if you start with a heavier-recoiling round, the absolute amount of recoil energy reduction is greater. Roy is really talking about efficiency--brakes are most efficient when used with high-pressure cartridges.]
Installation is Key to Accuracy
Roy’s findings are fascinating and suggest that further study of muzzle brakes is warranted. But we can all agree that precision installation of the brake is essential for accuracy. A poorly-installed, mis-aligned brake will degrade accuracy, that is well-known.
Harrell’s Precision has made thousands of muzzle brakes, in many styles and port arrangements. The Harrell brothers offer some good advice for gunsmiths installing brakes: “Muzzle brakes aren’t magic, they reduce recoil by redirecting exiting gas. What’s important is that they are straight and the threads are perpendicular with the base. The only way to get the base and threads perpendicular is to thread, not tap, them on a lathe.”
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July 9th, 2014
Commentary by Robert Whitley
In recent years several major firearms component suppliers have promoted the idea of the “do-it-yourself” AR-15 build up. In one sense this is a good thing because it promotes peoples’ education and understanding of firearms, but the down side of this is some folks are assembling and modifying AR-15s without an understanding of the rifle and without the necessary skills and tools to do things properly. The net result of this “do-it-yourself” work can be an AR-15 that is non-functional, problematic or dangerous. Here are two examples of common issues with “do-it-yourself” modifications.
Opening Up the Ejection Port
One common modification for AR-15′s is the opening up of the ejection port. This is typically done to permit more room for ejection or loading of the rifle, and it is also typically done in conjunction with a side charging handle modification.
A common issue I have seen with this modification is that the person opening up the port removes the upper right hand carrier support and riding surface. The net result of this is that the carrier sits loose in the upper receiver when the bolt is in lock-up and this can have very detrimental effects on the function and accuracy of the AR-15. Below are more pictures of one that I saw recently.
Click Arrows to See all FOUR Pictures
Upper Receiver Harmed by Modification
Receiver Showing Gas Key Hits
Wrong Buffer Installed
Another common mistake is the use of an improper buffer with the rifle (i.e. like using a carbine buffer in a standard rifle length buffer tube). There are many after market buffers being sold out there, but if the wrong buffer is used with the rifle, it can allow the bolt carrier to cycle too far back so that the rear of the carrier gas key becomes the stop for the carrier (i.e. when it smashes into the upper part of the lower receiver – OUCH!).
We have even seen situations where the gas key is snapped right off the carrier from this, and it completely disables the rifle and can also cause extensive damage to the firearm as well. Unfortunately we have seen this situation far too often and it is clear that a person needs to fully understand how the buffer assembly works if “do-it-yourself” work is going to be done to the buffer assembly, since everything done to the buffer assembly has an effect on the rifle, its function and accuracy.
While I applaud the person who is self-reliant and has a “can do” attitude, the other side of this is when it comes to a firearm, “do-it-yourself” work should only be done when and if one fully understands the rifle and how it functions and how the work will affect the rifle.
AR-X Enterprises, LLC
199 North Broad Street
Doylestown, PA 18901
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July 2nd, 2014
Want to shoot better scores at your next match? Here’s a smart, inexpensive do-it-yourself project from the good folks at Criterion Barrels. For less than one dollar in materials, in just a few minutes you can create a handy, effective mirage shield, custom-fitted to your favorite rifle.
All precision shooters should be familiar with mirage, a form of optical distortion caused primarily by variations in air temperature. Savvy shooters will use mirage as a valuable tool when gauging wind speed and direction. Natural mirage is unavoidable, but there are many techniques designed to limit its influence in long-range marksmanship.
A form of mirage can be produced by the barrel itself. Heat rising from the barrel may distort sight picture through your optics, leading to erratic results. Mirage caused by barrel heat can be reduced dramatically by a simple, light-weight mirage shield.
How to Make a Mirage Shield
A mirage shield is an extremely cost-effective way to eliminate a commonly-encountered problem. Making your own mirage shield is easy. Using old venetian blind strips and common household materials and tools, you can construct your own mirage shield for under one dollar.
1. Vertical PVC Venetian blind panel
2. Three 1”x1” pieces adhesive-backed Velcro
3. Ruler or tape measure
4. Scissors or box cutter
5. Pencil or marker
1. Measure the distance from the end of the receiver or rail to the crown of the barrel.
2. Using a pencil and ruler, measure the same distance and mark an even line across the blind.
3. Cut across the line using scissors or a box cutter, shortening the blind to the required length. (Remember, measure twice, cut once!)
4. Expose the adhesive backing on the loop side of the Velcro. Center and apply the Velcro strips on the barrel at regular intervals.
5. Expose the adhesive backing of the fuzzy side of the Velcro.
6. Place the blind on the upper side of the barrel. Apply downward pressure. Once the Velcro has secured itself to the barrel, separate the two sides. Proceed to mold both sides of the Velcro to fit the contour of their respective surfaces.
7. Reaffix the blind. Barrel related mirage is now a thing of the past!
How to Remove and Re-Attach the Mirage Shield
Removal of your mirage shield is accomplished by simply removing the blind. You can un-install the Velcro by pulling off the strips and then gently removing any adhesive residue left behind using an appropriate solvent. (Simple cooking oil may do the job.) Caution: With fine, high-polish blued barrels, test any solvent on a non-visible section of the barrel. Before storing the gun, re-oil the barrel to remove active solvents and residual fingerprints.
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July 1st, 2014
A while back, Sinclair International’s Reloading Press Blog featured a “round-table” discussion of reloading techniques. Sinclair’s team of tech staffers were asked: “What do you feel is the one-most crucial step in precision reloading?”
Here are their responses (along with comments from our Editors):
Phil Hoham: “I feel that when working up a load do not go too high or too low in your powder charge. Stay away from “suggested loads” you hear at the range, or on the internet. Always be sure to use a published reloading manual that presents not only minimums and maximums, but also pressure, velocity, and a proper range of powders used. Do not get distracted in the reloading process, and remain focused at all times during each step involved.”
AccurateShooter.com: Some loads presented on the Internet are OK as a starting point, but it is absolutely critical to understand that pressure maximums will vary considerably from one rifle to another (of the same chambering). For example, one 6mmBR rifle shooting 105gr bullets can max out with 30.0 grains of Varget powder, while another rifle, with the same chamber dimensions, but a different barrel, could tolerate (and perform better) with half a grain more powder. You need to adjust recommended loads to your particular rifle and barrel.
Pete Petros: “This could be a very broad topic, but if I were to pick one, it would be making sure to pay close attention, and weigh each and every powder charge to ensure that each load is exact and consistent. This is important not only for accuracy, but also for safety reasons.”
AccurateShooter.com: If you’re shooting beyond 200 yards, it is critical to weigh your loads with an accurate scale. Loads that are uniform (within a few kernels) will exhibit lower Extreme Spread and Standard Deviation. And remember, even if you stick with the same powder, when you get a new powder lot, you may have to adjust your load quite a bit. For example, .308 Palma shooters have learned they may need to adjust Varget loads by up to a full grain from one lot of Varget to the next.
Ron Dague: “I feel that the most important step(s) in reloading for accuracy are in the initial case prep. Uniforming the primer pocket to the same depth to ensure consistency in primer seating is a crucial step. Additionally de-burring the flash holes, each in the same way to clean up and chamfer the inside is important. It ensures that the ignition from the primer is uniform and flows out in the same consistent pattern. Doing so will create uniform powder ignition and tighten up your velocity Extreme Spread.”
AccurateShooter.com: With some brands of brass, primer pocket uniforming and flash-hole deburring is useful. However, with the best Lapua, Norma, and RWS brass it may be unnecessary, or worse, counter-productive. So long as your Lapua brass flash-holes are not obstructed or smaller than spec, it may be best to leave them alone. This is particularly true with the small flash holes in 220 Russian, 6BR, and 6.5×47 cases. MOST of the flash-hole reaming tools on the market have cutting bits that vary in size because of manufacturing tolerances. We’ve found tools with an advertised diameter of .0625″ (1/16″) that actually cut an 0.068″ hole. In addition, we are wary of flash-hole deburring tools that cut an aggressive inside chamfer on the flash-holes. The reason is that it is very difficult to control the amount of chamfer precisely, even with tools that have a depth stop.
Rod Green: “I feel that bullet seating is the most important step. If you had focused on making sure all prior steps (case prep, powder charge, etc.) of the process have been carefully taken to ensure uniformity, bullet seating is the last step, and can mean all the difference in the world in terms of consistency. Making sure that the bullet is seated to the same depth each time, and time is taken to ensure that true aligned seating can make the load.”
Bob Blaine: “I agree with Rod. I strongly feel that consistent bullet seating depth is the most important step in creating the most accurate hand loads. I have seen the results in both my bench and long range rifles. Taking the time to ensure exactness in the seating process is by far, the number one most important step in my book.”
AccurateShooter.com: Agreed. When loading match ammo, after bullet seating, we check every loaded round for base of case to ogive length. If it varies by more than 3 thousandths, that round is segregated or we attempt to re-seat the bullet. We measure base of case to bullet ogive with a comparator mounted on one jaw of our calipers. You may have to pre-sort your bullets to hold the case-base to ogive measurement (of loaded rounds) within .003″.
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June 27th, 2014
Over the years, noted gunsmith and a Benchrest Hall-of-Fame inductee Thomas ‘Speedy’ Gonzalez has learned a few things about “tuning” rear sandbags for best performance. On his Facebook page, Speedy recently discussed how sand bag fill levels (hard vs. soft) can affect accuracy. Speedy says you don’t want to have both your front and rear sandbags filled up ultra-hard. One or the other bag needs to have some “give” to provide a shock-absorbing function (and prevent stock jump).
SAND BAGS & HOW TO FILL THEM by Speedy Gonzalez
I was asked several times by competitors at the S.O.A. Matches and F-Class Nationals as to how I fill my sand bags for benchrest competition. Here is a copy of a reply I gave several years ago:
Back in the old days, about the time Fred Flintstone was still alive, I worked for Pat McMillan for free, from time to time to learn all his secrets. One day little Speedy was filling some new sand bags out behind Pat’s shop, stuffing them with more sand than Taco Bell put beans in their Burritos. When Pat stepped out the back door and inquired as to what in the hell was I doing packing them there bags the way I was.
I looked up at him with eyes like a kid with his hands in a cookie jar. My reply must have sounded like Homer Simpson “Doooh”. Finally I said “I don’t know, Boss. I just thought you were supposed to fill these babies up and go shoot. I got that ‘You dumb bastard look’ from Pat and I knew it was lecture time. This was what he told me:
You can not have two bags filled so hard that you gun bounces on them in the process of firing round at your target, especially if you have a rig with a very flexible stock. The bags must be set up in a manner for them to absorb the initial shock of the firing pin moving forward and igniting the primer. Then [they must] maintain their shape and absorb the second shock wave as well the rearward thrust and torque of the rifle. What happens to the rifle when this is not done? Well let me tell you. The rifles have a very bad tendency to jump and roll in the bags. This causes many of those wild, lost shots that one can’t explain.
Charles Huckaba, Ken Terrell, Larry Baggett, Ralph Stewart and some of us Texas shooters talk about this phenomena quite often. We have all agreed that:
- 1: You can not have two hard bags [i.e. both front AND rear] in your set-up.
- 2: Heavy sand magnifies these phenomena.
- 3: If you are a bag squeezer, pack ears hard and leave bag pliable enough to squeeze for the movement required. You may pack front bag as hard as rules permit.
- 4: Free recoil shooters pack both bags firm, but not so hard as to allow stock jump. Especially if you have a stock with a very flexible forearm.
- 5: We use play-ground sand, also know as silica sand. I sift mine to get any large impurities out then mix it with 25% to 50% with Harts parakeet gravel to the desired hardness that I am looking for. The bird gravel keeps the sand from packing itself into that solid as a brick state.
Speaking of bricks — another thing that happens when shooters employ that heavy zircon sand is the ears form a low spot under them from recoil and then tend to rock back and forth with the rifle causing many low shots to crop up. Edgewood makes an Edgewood/Speedy rear bag specially reinforced under the ears to eliminate this scenario.
One last note –If you use the Cordura bags keep them sprayed with a good silicon spray or “Rain-Ex”. This keeps them from getting sticky. Hey guys, try that and see if it helps. — Speedy
P.S.: I do not like the solid double-stitched leather bottoms. While this seems like a good idea, I see more shooters have problems because of them. They tend to slide around the bench and or slide with the rifle on recoil. The standard Protektor with Cordura rabbit ears and an Otto ring bag with a Cordura front would be what I would suggest to the new shooter or one of the Edgewood / Speedy rear bags, these mimic the “Donut” and feature a ring of leather around the bottom circumference that keep the bottom from rocking on the bench or ground if that is where you reside these days…
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June 8th, 2014
Laminated wood stocks offer an excellent combination of price and performance, and they can be obtained in a myriad of styles to suit your discipline — hunting, benchrest, tactical, silhouette, or high power. Laminated stocks can be a little trickier to finish compared to a hardwood such as walnut, as laminates are often delivered in bright or highly contrasting colors. Traditional wood finishes can alter the colors. Also, filling the pores in laminated stocks is an issue.
Automotive clear-coat products have become popular for finishing laminated wood stocks because they won’t alter the stock’s colors, and the clear-coat provides a durable weather-resistant finish. Clear-coat is also easy to “touch up” and it fills pores better than some other alternatives. Mike Ricklefs has written a comprehensive article on stock painting that includes a special section on clear-coating over laminated woods. If you want to clear-coat a stock, Mike’s article is a must-read!
In that Stock Painting Article, Mike offers these tips:
When finishing laminated stocks with clear-coat, you need to prepare the wood carefully, and build up quite a few thin layers one at a time. Begin by sanding, with progressively finer paper, all the way to 400 grit. Certain laminated stocks are so rough when they come from the stock-maker, that you may have to be very aggressive at first. But be careful with angles and the edges of flats. You don’t want to round these off as you sand.
After sanding, use compressed air to blow out all dust from the pores of the wood. This is very important to avoid a “muddy” looking finish. If you don’t blow the dust out with air before spraying the clear it will migrate out as you apply the clear. Also, after each sanding session, clean your painting area to remove excess dust. I also wet down the floor of my spray booth to keep the dust down.
Some painters recommended using a filler to close the pores. That’s one technique, but the filler can detract from the clarity of the final finish. Rather than use a pore-filling sealer, I use a high solids or “build” clear for the initial applications. This is slightly thicker than “finish” clear and does a good job of sealing the pores. Three (3) fairly heavy coats of “build” clear are applied. If you get a thick spot or a run in the finish at this point, it is not the end of the world but this does create more sanding work.”
There is a helpful thread in our Shooters’ Forum that discusses the use of clear-coating on laminated stocks. Member BHoges offered this advice: “Stick with Diamont, Glassurit, and Spies. If anyone has questions, I painted cars for a long time.”
Forum member Preacher, whose bolt-action pistol is shown in the photo below, states: “I buy my two-part clear-coat from the local NAPA dealer. They recommended Crossfire mixed 4:1. I really like the end results. There are six coats on that stock that were sanded down to bare wood for the first two, and then 600 wet-sanded for the other four coats. Two to three coats would be sufficient if the pores were filled first, but I would rather fill ‘em with the clear as it seems to make it appear deeper and I have the time to devote to it. I have PPG’s Deltron DC 3000 clear-coat on a few stocks of mine, but I like the NAPA better price wise, and it seems to hold up just as good as the Deltron.”
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June 1st, 2014
When we first ran this story a while back, it generated great interest among readers. By popular request, we’re reprinting this story, in case you missed it the first time around. — Editor
Precision shooters favor premium brass from Lapua, Norma, or RWS. (Lake City also makes quality brass in military calibers.) Premium brass delivers better accuracy, more consistent velocities, and longer life. Shooters understand the importance of good brass, but many of us have no idea how cartridge cases are actually made. Here’s how it’s done.
The process starts with a brass disk stamped from strips of metal. Then, through a series of stages, the brass is extruded or drawn into a cylindrical shape. In the extrusion process the brass is squeezed through a die under tremendous pressure. This is repeated two or three times typically. In the more traditional “draw” process, the case is progressively stretched longer, in 3 to 5 stages, using a series of high-pressure rams forcing the brass into a form die. While extrusion may be more common today, RWS, which makes some of the most uniform brass in the world, still uses the draw process: “It starts with cup drawing after the bands have been punched out. RWS cases are drawn in three ‘stages’ and after each draw they are annealed, pickled, rinsed and subjected to further quality improvement measures. This achieves specific hardening of the brass cases and increases their resistance to extraordinary stresses.” FYI, Lapua also uses a traditional draw process to manufacture most of its cartridge brass (although Lapua employs some proprietary steps that are different from RWS’s methods).
Deep-Draw Ram Illustration from Demsey Mfg.
After the cases are extruded or drawn to max length, the cases are trimmed and the neck/shoulder are formed. Then the extractor groove (on rimless cases) is formed or machined, and the primer pocket is created in the base. One way to form the primer pocket is to use a hardened steel plug called a “bunter”. In the photos below you see the stages for forming a 20mm cannon case (courtesy OldAmmo.com), along with bunters used for Lake City rifle brass. This illustrates the draw process (as opposed to extrusion). The process of draw-forming rifle brass is that same as for this 20mm shell, just on a smaller scale.
River Valley Ordnance explains: “When a case is being made, it is drawn to its final draw length, with the diameter being slightly smaller than needed. At this point in its life, the head of the draw is slightly rounded, and there are no provisions for a primer. So the final drawn cases are trimmed to length, then run into the head bunter. A punch, ground to the intended contours for the inside of the case, pushes the draw into a cylindrical die and holds it in place while another punch rams into the case from the other end, mashing the bottom flat. That secondary ram holds the headstamp bunter punch.
The headstamp bunter punch has a protrusion on the end to make the primer pocket, and has raised lettering around the face to form the headstamp writing. This is, of course, all a mirror image of the finished case head. Small cases, such as 5.56×45, can be headed with a single strike. Larger cases, like 7.62×51 and 50 BMG, need to be struck once to form a dent for the primer pocket, then a second strike to finish the pocket, flatten the head, and imprint the writing. This second strike works the brass to harden it so it will support the pressure of firing.”
Thanks to Guy Hildebrand, of the Cartridge Collectors’ Exchange, OldAmmo.com, for providing this 20mm Draw Set photo. Bunter photo from River Valley Ordnance.
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May 30th, 2014
What anti-corrosion products really fight rust effectively? You’ll hear many opinions, but what do actual field tests reveal? One rifle shooter, who posts on YouTube as BlueonGoldZ, wanted to separate myth (and marketing claims) from reality, so he completed his own long-term rust test using metal samples. First he used ordinary tap water spray, and then he did a second, longer-duration test with a salt-spray solution. Nine different products were tested: Break Free CLP, Corrosion-X, Frog Lube, M-Pro 7, Outers, Pro-Shot Zero Friction, Rem Oil, Slip 2000, and Tetra Gun Triple Action CLP.
BlueonGoldZ initially examined each product for its “beading” properties with a normal tap water spray. But the main test involved many multiple weeks of exposure after a “dense” salt-water spray. (No rust formed after two weeks tap water exposure, so the test was accelerated with salt-water exposure).
See Results of Anti-Corrosion Product Test in Video
YouTube Link: http://youtu.be/uOB5eCReAQY
The clear winners in the test, as shown by the screen shot below, were Corrosion-X (Best), and Frog-Lube (Second Best). The photo shows the test samples two weeks after being sprayed with salt water. The results are pretty dramatic — you can see with your own eyes what happened. We think this is a very useful bit of real-world research.
Results from Similar Long-Term Salt Exposure Test
Unfortunately, BlueonGoldZ’s test did NOT include Eezox, which we have found to be extremely effective (on a par with Corrosion-X). In another long-term test of corrosion preventatives, the two best rust fighters were Eezox and Corrosion-X in that order. Since that test was completed, Corrosion-X, already an excellent product, has been enhanced. CLICK HERE for Long-Term Salt Exposure Test Report.
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May 28th, 2014
While attending the CA Long Range Championship a while back, we had the opportunity to test the performance of a high-magnification (63X) spotting scope in near-ideal conditions (maybe the best I’ve ever witnessed). On the event’s last day we arrived at 5:45 am, literally as the sun was cresting the horizon. I quickly deployed our Pentax PF-100ED spotting scope, fitted with a Pentax SMC-XW 10mm fixed-power eyepiece. When used with the 100mm Pentax scope, this 10mm eyepiece yields 63X magnification. Befitting its $359.00 price, this eyepiece is extremely clear and sharp.
At the crack of dawn, viewing conditions were ideal. No mist, no mirage, no wind. The first thing this Editor noticed was that I could see metal nail heads on the target boards. That was astonishing. As soon as the first practice targets went up, to my surprise, I could see 6.5mm, 7mm, and 30-caliber bullet holes in the white at 1000 yards.
That’s right, I could see bullet holes at 1000. I know many of you folks may not believe that, but there was no mistaking when I saw a 7mm bullet cut the white line separating the Nine Ring and Eight Ring on the target in view. (I was watching that target as the shot was fired and saw the shot-hole form). And when I looked at the 30-cal targets, the bullet holes in the white were quite visible. In these perfect conditions I could also make out 3/8″ bolt heads on the target frames.
The Human Factor
When viewing the bullet holes, I was using my left naked eye (no safety glasses or magnification). I also had a contact lens in my right eye (needed for distance vision). To my surprise, while I could see the bullet holes without much difficulty with my left eye, things were fuzzier and slightly more blurry with the right eye, even when I re-focused the scope.
Then I invited 3 or 4 shooters to look through the scope. One younger guy, with good eyes, said immediately: “Yeah, I can see the holes — right there at 4 o’clock and seven o’clock. Wow.” Some older guys, who were wearing glasses, could not see the holes at all, no matter what we did to the scope’s main focus and diopter adjustment.
The lesson here — if you have to wear glasses or corrective contact lenses, just that extra bit of optical interference may make a difference in what you can see through the scope. Basically anything that goes between the scope eyepiece and your eyeball can degrade the image somewhat. So… you may be better off removing your glasses if you can still obtain good focus sharpness using the diopter adjustment and focus ring. I did the left vs. right eye test a half dozen times, and I could definitely see small features at 1000 yards with my naked eye that I could not see with my right eye fitted with a contact lens. (I did have to re-focus the scope for each eye, since one had a corrective lens while the other did not.)
Mirage Degrades Image Sharpness and Resolution
The “magic light” prevailed for only an hour or so, and then we started to get some mirage. As soon as the mirage appeared I was no longer able to see raw bullet holes, though I could still easily see black pasters on the black bulls. When the mirage started, the sharpness of the visible image degraded a huge amount. Where I could see bullet holes at dawn, by mid-morning I could barely read the numbers on the scoring rings. Lesson: If you want to test the ulimate resolution of your optics, you need perfect conditions.
Chromatic Aberration Revealed
As the light got brighter and the mirage increased I started to see blue and red fringing at the edges of the spotting disk and the large numerals. This was quite noticeable. On one side of the bright, white spotting disc you could see a dark red edge, while on the other side there was a blue edge (harder to see but still present).
The photo below was taken through the Pentax spotter lens using a point and shoot camera held up to the eyepiece. The sharpness of the Pentax was actually much better than this photo shows, but the through-the-lens image does clearly reveal the red and blue fringing. This fringing is caused by chromatic aberration — the failure of a lens to focus all colors to the same point. Chromatic aberration, most visible at high magnification, causes different wavelengths of light to have differing focal lengths (see diagram). Chromatic aberration manifests itself as “fringes” of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis. Keep in mind that the Pentax does have “ED” or low-dispersion glass, so the effect would be even more dramatic with a cheaper spotting scope.
If you wonder why top-of-the-line spotting scopes (such as the $3900 Leica APO-Televid 82) cost so much, the answer is that they will deliver even LESS chromatic aberration at long range and high magnification. With their exotic apochromatic (APO), ultra-low-dispersion glass, a few ultra-high-end spotting scopes can deliver an image without the color edging you see in the photo above.
The Pentax PF-100ED is a heck of a spotting scope. Any scope that can resolve bullet holes at 1000 yards is impressive. But if you want the ultimate in optical performance, with minimal chromatic aberration, you may need to step up to something like the 88mm Kowa Prominar TSN-883 with Flourite Crystal lenses ($2450.00 body only), or the 82mm Leica APO ($3899.00 with 25-50X eyepiece).
EDITOR’s NOTE: The purpose of this report is to show what is possible… in IDEAL conditions. With this Pentax 100mm, as well as a Swarovski 80mm, we have often been able to resolve 6mm bullet holes at 600 yards. But again, that performance requires really good viewing conditions. By 10:00 am at my range, even with the 100mm Pentax at 75 power, seeing 6mm bullet holes is “iffy” at best. So don’t go out and mortgage the house to buy a $4000 optic with the hope that you’ll be able to spot your shots at 1000 yards. If conditions are anything less than perfect, you’ll be lucky to see bullet holes at 500 yards. The real solution for very long-range spotting is to set up a remote target cam that broadcasts a video picture to a screen at your shooting station.
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May 21st, 2014
There is nothing more frustrating (or embarassing) than sending a live round into your expensive new chronograph. As the photo below demonstrates, with most types of chronographs (other than the barrel-hung Magnetospeed), you can fatally injure your expensive chrono if it is not positioned precisely.
When setting up a chrono, we always unload the rifle, remove the bolt and bore-sight to ensure that the path of the bullet is not too low. When bore-sighting visually, set up the rifle securely on the sandbags and look through the bore, breech to muzzle, lining up the barrel with your aim point on the target. Then (during an appropriate cease-fire), walk behind the chronograph. Looking straight back through the “V” formed by the sky-screens, you should be able to see light at the end of the barrel if the gun is positioned correctly. You can also use an in-chamber, laser bore-sighter to confirm the visual boresighting (see photo).
Adjust the height, angle and horizontal position of the chronograph so the bullet will pass through the middle of the “V” below the plastic diffusers, no less than 5″ above the light sensors. We put tape on the front sky-screen supports to make it easier to determine the right height over the light sensors.
Use a Test Backer to Confirm Your Bullet Trajectory
You can put tape on the support rods about 6″ up from the unit. This helps you judge the correct vertical height when setting up your rifle on the bags. Another trick is to hang a sheet of paper from the rear skyscreen and then use a laser boresighter to shine a dot on the paper (with the gun planted steady front and rear). This should give you a good idea (within an inch or so) of the bullet’s actual flight path through the “V” over the light sensors. Of course, when using a laser, never look directly at the laser! Instead shine the laser away from you and see where it appears on the paper.
Alignment of Chronograph Housing
Make sure the chrono housing is parallel to the path of the bullet. Don’t worry if the unit is not parallel to the ground surface. What you want is the bullet to pass over both front and rear sensors at the same height. Don’t try to set the chrono height in reference to the lens of your scope–as it sits 1″ to 2″ above your bore axis. To avoid muzzle blast interference, set your chronograph at least 10 feet from the end of the muzzle (or the distance recommended by the manufacturer).
Rifles with Elevated Iron Sights
All too often rookie AR15 shooters forget that AR sights are positioned roughly 2.4″ above the bore axis (at the top of the front sight blade). If you set your bullet pass-through point using your AR’s front sight, the bullet will actually be traveling 2.4″ lower as it goes through the chrono. That’s why we recommend bore-sighting and setting the bullet travel point about 5-8″ above the base of the sky-screen support shafts. (Or the vertical distance the chronograph maker otherwise recommends). NOTE: You can make the same mistake on a scoped rifle if the scope is set on very tall rings, so the center of the cross-hairs is much higher than the bore axis line.
TARGET AIM POINT: When doing chrono work, we suggest you shoot at a single aiming point no more than 2″ in diameter (on your target paper). Use that aiming point when aligning your chrono with your rifle’s bore. If you use a 2″ bright orange dot, you should be able to see that through the bore at 100 yards. Using a single 2″ target reduces the chance of a screen hit as you shift points of aim. If you shoot at multiple target dots, place them in a vertical line, and bore sight on the lowest dot. Always set your chron height to set safe clearance for the LOWEST target dot, and then work upwards only.
Other Chronograph Tips from Forum Members:
When using a chronograph, I put a strip of masking tape across the far end of the skyscreens about two-thirds of the way up. This gives me a good aiming or bore-sighting reference that’s well away from the pricey bits. I learned that one the hard way. — German Salazar
A very easy and simple tool to help you set up the chronograph is a simple piece of string! Set your gun (unloaded of course) on the rest and sight your target. Tie one end of the string to the rear scope ring or mount, then pull the string along the barrel to simulate the bullet path. With the string showing the bullet’s path, you can then easily set the chronograph’s placement left/right, and up/down. This will also let you set the chrono’s tilt angle and orientation so the sensors are correctly aligned with the bullet path. — Wayne Shaw
If shooting over a chrono from the prone position off a bipod or similar, beware of the muzzle sinking as recoil causes the front of the rifle to drop. I “killed” my first chronograph shooting off a gravel covered firing point where I’d not given enough clearance to start with and an inch or two drop in the muzzle caused a bullet to clip the housing. — Laurie Holland
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May 8th, 2014
This is an interesting technical article prepared by Action Target, a leading steel target manufacturer based in Provo, Utah. With technical data provided by the American Iron and Steel Institute in Washington D.C., this report is designed to cut through the recent hype and establish a basis of fact for accurate evaluation and comparison.
What Is Steel?
Steel is an alloy metal composed of iron and varying amounts of carbon and/or other elements such as chromium, nickel, tungsten, manganese, and so on. Steel with specific properties and characteristics is created by adjusting the overall chemical composition or by altering the various production processes such as rolling, finishing, and heat treatment. Because each of these factors can be modified, there is potentially no limit to the number of different steel recipes that can be created. Currently, there are over 3,000 cataloged grades or chemical compositions of steel available. Steel can utilize a wide variety of alloying elements and heat treatments to develop the most desirable combination of properties.
Steel Hardness and Quality
For steel targets to be functional and safe, they should be made of high quality through hardened steel that has a Brinell hardness number (BHN) of at least 500. The steel must also provide sufficient strength, toughness, and impact resistance. The Brinell hardness test depends upon the resistance offered to the penetration of a carbide steel ball (1.6 mm diameter) when subjected to a weight of 12.6 kg. The resulting hardness value is computed as the ratio of the applied load to the area of the indentation produced. This test is accepted as a worldwide standard for measuring the hardness of steel.
Truth — There are 2 Factors that Affect the Hardness of Steel
The first is the amount of carbon and other alloying elements in its chemical composition, and the second is the manner in which the heating and cooling of the steel is manipulated. These factors are determined at the most fundamental level, and affect the finished steel as a whole.
Truth — Steel Hardness is a Critical Issue
The hardness of the steel is critical because only a smooth surface will generate predictable splatter patterns. Steel that is not sufficiently hard can develop pits, craters, dimples, and other hazardous deformations. When a bullet hits one of these deformations, it is impossible to predict where the splatter will go, thereby creating an unacceptable training environment.
[Left] Hard steel with a flat surface will create a predictable splatter pattern.
[Right] Soft steel with an uneven surface will cause unpredictable and unsafe ricochet and splatter.
There are many steel mills located around the world, but only a select few are able to produce steel that is hard enough and of sufficient quality to be safely used for steel targets. HARDOX / SSAB, Bethlehem-Lucas, Oregon Steel Mills, and NKK are major producers of such steel. Each of these companies may have minor proprietary differences in their production methods, but they all must make sheets of hard steel in essentially the same way. Nevertheless, some suppliers of targets and shooting range equipment attempt to muddy the water and create perceived differences in steel quality where none exist. One particularly misleading claim refers to a certain company’s use of through hardened steel as opposed to merely surface hardened AR500 steel allegedly used by everyone else. We state the following with all possible force:
1. Action Target uses only high quality, through hardened steel with a Brinell hardness rating of at least 500, and we use it in every one of our ballistic steel products.
2. Action Target can also provide through hardened steel targets and other steel products with certified Brinell hardness ratings of 550 and even 600.
3. Despite the inaccurate claims, AR500 steel is NOT surface hardened. It is through hardened. Witness the quotes listed below from steel suppliers around the country.
Chapel Steel — AR500 is a quenched & tempered, through hardened, wear-resistant grade of abrasion resistant steel plate used for severe impact. (SOURCE: http://www.chapelsteel.com/ar500-ar500f.html)
Heflin Steel — Heflin REM 500 abrasion resistant plate is a premium grade wear plate, ideal for extreme abrasion coupled with resistance to impact. REM 500 plate is through hardened up to a 3″ thickness for maximum hardness and abrasion resistance.
Benco Steel — AR500 is a through hardened steel with high hardness for use where there is severe impact and abrasion.
(These companies are steel suppliers, not manufacturers or producers. They buy steel from the actual manufacturers like HARDOX / SSAB, and then re-sell it to their own customers.)
4. Any statements contrary to those above are simply untrue.
Be careful not to get caught up in the “more is better” mindset. Just because a Brinell hardness number (BHN) of 500 is good, it doesn’t mean a rating of 700 is better. While you must use steel that is hard enough for the task, going overboard only impacts your checkbook and not the product durability. For example, ballistic tests have shown that the performance difference between steel with a 500 BHN and steel with a 535 BHN is so small that you can’t tell the difference with a bullet but only with a gauge. Also be aware that you can actually use steel that is too hard and too brittle for ballistic training purposes
Story find by EdLongrange. We welcome reader submissions.
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