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August 19th, 2008
Denver Instrument, maker of the MXX and Timberline Series of precision balances, has created a helpful guide explaining how to get the best performance from a digital scale. Denver Instrument knows that, to achieve and maintain a very high level of accuracy with digital scales, they must be calibrated regularly, leveled properly, and kept away from sources of interference. Unfortunately, some reloaders treat their electronic scales as if the machines were toasters — something to place on a tabletop, plug into an outlet, then “set and forget.” There’s a better way to set up your scale and keep it functioning optimally. Here are ten guidelines provided by Denver Instrument. Follow these “TEN Commandments” and you’ll benefit:
 10 COMMANDMENTS OF GOOD BALANCE USE
ONE: Thou shalt choose the best resting spot. The performance of your balance depends greatly on the surrounding environment. Choose a location away from the main traffic flow of the room, especially doors. Also be aware of heating and cooling vents as these produce air movement. You can adjust the environmental settings on your balance to provide the best performance in the chosen location. Balances must be placed away from magnets as they affect the weigh cell performance.
TWO: Thou shalt avoid vibrations. Vibrations can come from large machinery in production environments and from fume hoods in laboratories. An alternative to fume hoods are Power Safety Workstations which are designed specifically for use with a balance.
THREE: Thou shalt watch temperature changes. On an analytical balance a one degree temperature change can cause a 1 digit (0.0001g) drift. Although Denver balances have temperature correction built-in, it is still important to calibrate your balance when the temperature changes significantly. Choosing to place your balance in a temperature controlled room, away from sunlight, and calibrating often helps minimize the effects of temperature.
FOUR: Thou shalt calibrate often. Upon installation and each time the balance is moved you should calibrate your balance. For example moving an analytical balance to a location that is only 13 feet higher changes the weight reading from 200.0000 g to 199.9997 g; which means the result is 0.0003 g lighter than the actual mass.
FIVE: Remember to check the level. The instrument should be leveled upon installation with all feet (two front feet for round pan units, four feet for square pan units) touching the countertop. If the level changes, the balance should be re-leveled and recalibrated. As an example, a 200g sample would weigh 0.0025 g less when tilted at an angle of 0.3°.
SIX: Honor thy weights. Keep in mind that weights are only as reliable as their quality and certification. Remember, a 1 g does not weigh precisely 1.00000 grams. Weights should be recertified annually. Denver Instrument offers recertification services on all weights 1 mg to 5 kg. Check to make sure you have selected the proper weight class for your balance. The weight tolerance should be better than balance readability. Always use tweezers or gloves when handling weights as smudges and indentations change the value of the weight. Keep weights in cases so they don’t get scratched or dusty.
SEVEN: Thou shalt always use a small container and weigh in the center of the pan. Especially when using an analytical balance, the effects of air buoyancy increase as the sample container size increases. Using a small sample container will minimize the effects. Items placed on the pan provide a downward force. Placing them directly in the center of the pan keeps corner loading errors at a minimum.
EIGHT: Thou shalt not unplug. To perform within published specifications balances must have power applied for 30 minutes to 48 hours depending on the resolution of the balance. Denver balances have a standby mode which turn the display to standby but keep power cycling through the electronics.
NINE: Thou shalt not ignore static. Static is one of the most common weighing “noises”. It can cause reading to appear too high, too low or just be unstable. Denver balances include grounding methods to reduce the effects of static. However sometimes extra supplies are needed. Consider anti-static weigh dishes, anti-static brushes or low tech ways to increase the humidity of the chamber like placing damp cotton balls or glass wool in a small vial in the corner of the analytical draft shield.
TEN: Thou shalt clean often. Dirty weigh pans and powder in weighing chamber can contribute to static issues and lead to a wide variety of problems. Denver weigh pans are made from stainless steel and can be cleaned using a variety of household and laboratory chemicals. A small paint brush can be used to get power away from the edges of the draft shield for easy clean up.
August 15th, 2008
Grant, one of our Forum members from New Zealand, asked if there was a universal shell-holder that could hold cartridges securely for neck-turning, trimming, and case prep. He complained that the screwdriver-type case holder he was using didn’t center easily, was hard to tighten, and the case sometimes came loose during rotation. Another forum member agreed that he has experienced the same problems using a screwdriver-type case-holder.
This editor has found that a K&M screwdriver-type case holder CAN work securely if you tighten the locking mechanism tightly with the supplied wrench. But then you need the wrench again to get the case OUT. We were interested to see if there was a better solution that held the case securely, yet was easy to lock and unlock without tools.
Forum member Gunamonth provided a solution: “I use a Lee Zip Trim three-jaw case holder. With a little practice it centers the case quite nicely and holds just about anything. Chuck it in a cordless drill and have at it. It is much better than either the K&M or Sinclair [case-holder] in my opinion and the Zip Trim jaw is a lot cheaper (about $12.00). To use with power, you also need the Zip Trim three-jaw spindle, which is another $2.00.”
August 1st, 2008
With the relentless pursuit of more velocity and the “next higher node” by many reloaders, it is important to pause and think about safety. And one has to remember that most brass will not hold up to high pressure the way Lapua or RWS does. Many readers have asked us: “How does one detect excess pressure?”. Well first, one can obviously monitor the primer pockets and measure the diameter of the case near the web. Excessive stretch or pocket loosening is a sure sign you’re running too hot. There are also many visible signs of over-pressure which you can see. Reader ScottyS provided this comparison photo of cases, showing the tell-tale signs of over-pressure.
Scotty tells us: “These samples were from a lot of Federal soft-point hunting ammunition that were fired in a custom .308 with a chamber on the tight side (although still allowing a .308 Winchester GO gauge). Among the pressure symptoms were heavy recoil, sticky bolt lift, and the left case had to be manually removed from the boltface. This demonstrates why: 1) you should never assume that all lots of factory ammo are the same (and safe); and 2) you should ALWAYS wear eye protection. This also shows how high pressure can spike once you approach maximum load levels.”
Scotty noted that there was a big pressure difference between the left case and the right case, although both were fired sequentially, and both were from the same lot of ammo. So take heed–always take precautions when testing new ammo, even if it is factory-loaded.
June 29th, 2008
 In Sierra Bullets’ X-Ring Quarterly Newsletter, you’ll find lots of useful info on ballistics and reloading. Among our favorite regular X-Ring features are the “Short Shots” offered by Sierra Technician Carrol Pilant. Here are some of Carrol’s tips.
General Reloading Advice
● When using a collet style case trimmer, try to tighten the collet down equally each time to keep lengths uniform. If you tighten it down hard, the case will be longer than one you tighten down lightly.
● A little lube on the pilot and cutter on a case trimmer every few cases will help keep it from trying to gall in the case mouth and helps keep the blades sharp and cutting smoothly. It makes trimming an easier task.
● When charging cases from a powder measure, use smooth uniform movement being sure to give powder time to fall into the powder drum chamber. Also be sure to give it time to fall into the case.
● When using mixed cases or cases that have been fired a different number of times, don’t be surprised to get erratic velocities and performance.
● Just because two bullets weigh the same doesn’t mean they can be loaded the same. The amount of bearing surface can vary drastically.
Photo by M. Dunlap
Handgun Reloading Tips
● In revolver cases, rather than try to seat and crimp in one stage, seat in one stage and crimp separately. You won’t have the bulge at the base of the crimp you often get when trying to do it in one stage.
● When roll crimping, if your cases are erratic lengths, your crimps will be erratic also. Cases should be trimmed to the same length.
June 28th, 2008
Three-gun match competitor Zak Smith employs a simple, handy means to store his elevation and wind dift data — a laminated data card. To make one, first generate a come-up table, using one of the free online ballistics programs such as JBM Ballistics. You can also put the information in an Excel spreadsheet or MS Word table and print it out. You want to keep it pretty small.
Below is a sample of a data card. For each distance, the card includes drop in inches, drop in MOA, drop in mils. It also shows drift for a 10-mph cross wind, expressed three ways–inches, MOA, and mils. Zak explained that “to save space… I printed data every 50 yards. For an actual data-card, I recommend printing data every 20 or 25 yards.” But Zak also advised that you’ll want to customize the card format to keep things simple: “The sample card has multiple sets of data to be more universal. But if you make your own data card, you can reduce the chance of a mistake by keeping it simple. Because I use scopes with MILS, my own card (bottom photo) just has three items: range, wind, drop in MILS only.”
Once you have the card you can fold it in half and then have it laminated at a local office store or Kinko’s. You can keep this in your pocket, tape it to your stock, or tie the laminated card to your rifle. If you regularly shoot at both low and high elevations, you may want to create multiple cards (since your ballistics change with altitude). To learn more about ballistic tables and data cards, check out the excellent “Practical Long-Range Rifle Shooting–Part 1″ article on Zak’s website. This article offers many other insights as well–including valuable tips on caliber and rifle selection.
June 25th, 2008
 Most rear sand-bags (from Edgewood, or Protektor, or SEB) are optimized for use on the bench with low-profile stock designs like the McMillan Edge or Kelbly Klub. If you use these bags when shooting from the ground F-Class style or with bipod, you may find the rifle is too low to the ground for comfort. Yes you can suck in your belly and crank down your front rest, but it makes more sense to elevate the rear bag. Jason Baney has a simple solution that costs under $4.00 in materials.
Get a small 12″x12″ section of 1″ thick plywood and trim it to fit the base of your bag, leaving maybe 1/2″ extra on all sides. Then get some rubberized, waffle-pattern GRIP-IT shelf-liner from your local home improvement center, and attach it to the underside of the wood. Alternatively, if you want a more rigid base (with less ‘give’) for hard, flat ground, use high-durometer unlined Neoprene, available from industrial supply shops. Glue a layer of shelf liner or Neoprene on the bottom and top of the plywood. This will give good grip on your shooting mat and provide a stable, non-slip surface for the base of your sandbag. If you need more elevation, just use a thicker piece of wood, or sandwich two pieces together. NOTE: We’ve used the shelf liner with zero problems on a concrete bench, but some folks say the shelf liner is too squishy for serious BR work. If you’re concerned about that, use the hard neoprene instead.
 If you need a riser with more mass, Dave Dohrmann sells high-durometer Neoprene riser pads in 1/2″ through 1″ thicknesses, starting at $22.00. Dave offers risers cut to fit both Protektor and Edgewood footprints. Call Dave at 864-884-0155 or email dbugholes[@]aol.com. With textured surfaces top and bottom, Dave’s heavy pads work equally well to elevate your bag on the bench.
June 16th, 2008
Your editor wins the dunce of the week award, but he learned an important lesson. This weekend I shot the Varmint Silhouette match at Ojai, California. In preparation for the match, I (wisely) went to a range on Thursday to chronograph my match load and confirm my 100-yard, no-wind zero. All went well there, and after three sighters I put three rounds into 0.260″ right at point of aim. So far, so good.
| Editor moves his scope AFTER zeroing. End result? Zero shifts 2 MOA up and 11.5 MOA right. Yikes! |
 But, while testing, I noted that the scope, having been positioned for prone shooting, was much too far forward. It needed to be moved back about an inch for comfortable shooting at the bench.
No problem I think… I take the gun home, get my Leupold Torx wrench and loosen the rings. Now, I use Burris Signature rings, the ones with the plastic inserts that provide elevation preload: +10 in the rear and a -10 in the front. These are net values, created with pairs of +05 (thicker) and -05 (thinner) half-ring inserts. In the back the thicker +05 insert is on the bottom and thinner -05 on top, while in the front the thicker insert is on the top with the thinner on the bottom.
First thing I note when moving the scope is that it was hard to set the inserts in exactly the same spot (though I tried). I also note that the inserts seemed to flatten out or squeeze down more when I re-tensioned the ring bolts.
I figured I might have to make a minor correction to my zero at the range, so I wasn’t too concerned. Boy was I wrong.
Windage off Six Feet at 600 Yards
At the match, I dialed in my 600-yard come-up and aimed at a steel gong we use for sighter shots. Normally I can “certify” my 600-yard zero in three shots. This time, my spotter couldn’t even see the hits. “WTF”, I think… Then another shooter notes that my bullets are impacting about SIX FEET to the right of the Gong and about a foot too high.
I had to dial in 46 clicks (11.5 MOA) of left windage to get back on the Gong. At 600 yards, one MOA is 6.282 inches. My 600-yard Point of Impact had shifted 72″ to the right — a full six feet! That’s huge. That’s like being off a foot at 100 yards.
LESSON LEARNED: If you make ANY change to your scope, you should re-zero.
SIGNATURE RING LESSON LEARNED: If you are running the Burris Signature Rings, with plastic inserts, the change in POI when you move the scope can be extreme — way more than you’d expect with conventional rings. The plastic inserts take a different “set” each time you tension the rings, even if you do your best to maintain the inserts’ orientation in the rings. No matter how careful you are, those plastic inserts aren’t going to hold the scope in exactly the same place.
So, if you don’t want to win the Dunce Award like I did, make sure you re-test your scope’s zero AFTER you move the fore-and-aft position, and EVERY time you re-tension Burris Signature Rings. It’s worth noting that the ring set in question is five years old and it held zero perfectly until I decided to move the scope back. This was done because my club recently built benches at the 600-yard line so we now shoot from the bench rather than prone, F-Class style.
May 31st, 2008
Summer’s here, and that means hot weather and lots of mirage. A quality mirage shield reduces the amount of optical distortion caused by heat waves rising from the barrel directly in front of the scope. On a hot day, after many rounds through the barrel, the benefit of a mirage shield can be quite dramatic. Benchrest shooters have used mirage shields for many years. Mirage shields can be just as beneficial for the serious varmint shooter. But, curiously, most varminters we know don’t employ mirage shields. We think they should. A mirage shield is a low-cost accessory that helps you get more hits and fewer misses.
As our friend Boyd Allen observed: “Varminters should use mirage shields. Think about it. You’ve invested thousands of dollars in a fancy varmint rifle and quality scope. You may have spent hundreds of dollars traveling to the varmint fields and spent dozens of hours loading up your ammo. Without a mirage shield on your barrel, once that barrel gets hot, you WILL get mirage effects that can make you miss a shot. A mirage shield costs just a few dollars. It really doesn’t make sense to go out to the varmint fields without one, if you plan on shooting lots of rounds. Barrel heat mirage can cause you to miss that critter, even if you have the most accurate rifle in the world.”
Dan Lilja offers a nice, wide mirage shield for $10. Dan notes: “Our benchrest mirage shield also works very well for field varmint rifles if there is a lot of action and the barrel is getting hot. The shield deflects image-distorting heat waves that come off of a hot barrel. The heat flows out past the edge of the shield and out of the line-of-sight of the rifle scope. These shields are 18” long, made of thin painted steel (like window blind material) and can be easily trimmed to length.”
Sinclair International also offers a 2″-wide venetian-blind style Mirage Shade, that costs just $4.25. It is available in two lengths, 18″ for BR barrels (item 06-7200), and 24″ for longer varmint barrels (item 06-7300). The Sinclair Shade is made of aluminum and can easily be trimmed to a shorter length. Like the Lilja shield, the Sinclair Mirage Shade attaches with adhesive-backed Velcro fasteners.
May 29th, 2008
Here’s an inexpensive tip that can help you load straighter ammo, with slightly better measured concentricity (i.e. less run-out) on the case necks and bullets. Simply use a rubber O-Ring on the underside of the die locking ring. This allows the die to self-align itself (slightly) to the case that is being sized. Without the O-Ring, if the flat surface on the top of your press is not perfectly square with the thread axis, your die can end up slightly off-angle. This happens when the bottom of the locking ring butts up tight against the top of the press.
Top prone shooter German Salazar has tried this trick and he says it works: “Go to your local hardware store and get a #17 O-Ring (that’s the designation at Ace Hardware, don’t know if its universal). Slip the O-Ring on the die and re-adjust the lock ring so that the O-Ring is slightly compressed when the die is at the correct height. Size and measure a few more cases. You will probably see a slight improvement in neck concentricity as the die can now float a bit as the case enters and leaves it. This isn’t going to be a dramatic improvement, but it’s a positive one.”
Lee Precision makes die lock rings with built-in O-Rings. Lee’s distinctive lock ring design allows the same kind of self-alignment, which is good. However, Lee lock rings don’t clamp in place on the die threads, so they can move when you insert or remove the dies — and that can throw off your die setting. By using an O-Ring under a conventional die lock ring, you get the advantages of the Lee design, without the risk of the lock ring moving.
May 19th, 2008
Gunsmith Nat Lambeth, nlambeth [at] embarqmail.com, recently had a client bring in a Custom-Shop Remington that wouldn’t even hold one Minute of Angle (MOA) at 100 yards. Nat was able to correct flaws in the factory action and then fit a new barrel. Remarkably, after action truing and barrel replacement, the gun shot like a house on fire. After working his magic, Nat shot a 0.111″ 5-shot group with the gun.
Nat tells us: “I had a customer bring in a Remington 700. This rifle was supposed to have been from the custom shop. It was a stainless model 700 with a 5R Mil Spec barrel in a HS Precision stock. The customer paid a premium price for this rifle. The customer complained the rifle ‘won’t shoot groups under 1.5″ at 100 yards’, and he wanted a new barrel. He had 400 rounds down the tube. The barrel looked to be in good shape with maybe a scratch 8 inches from the muzzle.
Blue-Printing the Receiver
I removed the barrel from the receiver and looked at the internal bolt lug engagement surfaces. Only one lug seemed to be contacting. I put the bolt in a V-Block and measured the rearward bolt lug surfaces. The right or bottom lug had .019″ more reaward surface than the left or upper lug. This would have taken me two days to lap out so I set up the bolt in a truing jig and turned the bolt .020. I then put the action in a action truing jig and machined the inside lug surfaces until I got one even surface. I lapped the lugs until I had 80% bi-lateral contact, then re-faced the bolt and action face.
New Broughton Barrel
I dialed in a new 26″ Broughton 1:10, 5C barrel. It was indicated on both ends until a .0001″ indicator needle was not moving. The barrel was turned, threaded, and chambered in the same setup using thinbit tooling, a PT&G 95 Palma reamer with a .3004 bushing. The chamber was cut within .0015″ with a Lambeth/Kiff Micrometer Adjustable Reamer Stop. The factory recoil lug was replaced with a precision-ground lug.
The barrel was removed from the lathe and the muzzle was cut 1.250 shorter in a bandsaw. The barrel was re-mounted in the lathe and the muzzle dialed in the steady rest. The crown was faced with a piloted, PT&G facing tool then faced with a piloted, 79° counter bore .100″.
Stock Work
The rifle stock was re-inletted and glassed in for two inches. Then the barrel free-floated.
A Tack-Driver is Born
I thoroughly prepped 22 pieces of used 308 Federal Gold match brass, which were then loaded with 42.5 grains of H4895, CCI BR2 primers, and Hornady 168 HPBT bullets. After cleaning the barrel, I fired one test round with no problems and cleaned the barrel again. I then installed a Leupold 6.5-20AO scope in Farrell bases and rings. I bore-sighted the rifle by eye with the bolt removed at 50 yards.
After some sighters to set Point of Aim, I sat down and did 5 shots for record at 100 yards. Those five shots went into one ragged hole. (See Target Below — this editor measures the group as 0.111″ center to center using OnTarget Software.) Another customer who was there at the range, then shot a 5-shot group that went into 0.312″. That’s an 0.2115″ average for the two groups. I then was able to shoot a couple more groups in the ‘teens.”
Conclusion
Nat proved that attention to detail DOES make a difference, and that truing an action, improving the bedding, and fitting a superior barrel can make a HUGE difference in accuracy. Now, mind you, we’re not suggesting that you can take a factory .308 and make it into a gun that will win the Super Shoot. Nat’s 0.111″ group was exceptional. Still this demonstrates that major gains can be had by action blue-printing combined with bedding work and a new barrel.
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