When your cases become hard to extract, or you feel a stiff bolt lift when removing a cartridge, it’s probably time to full-length size your cases, and “bump” the shoulder back. With a hunting load, shoulder bumping may only be required every 4-5 loading cycles. Short-range benchrest shooters, running higher pressures, typically full-length size every load cycle, bumping the shoulder .001-.002″. High Power shooters with gas guns generally full-length size every time, and may need to bump the shoulders .003″ or more to ensure reliable feeding and extraction.
Use Shims for Precise Control of Shoulder Bump
Some shooters like to set the “default” position for their full-length die to have an “ample” .003″ or .004″ shoulder bump. When they need less bump, a simple way to reduce the amount of shoulder movement is to use precision shims in .001″ (one-thousandth) increments.
Here are reports from Forum members who use the shims:
“Great product. I have my die lock ring(s) adjusted for the shortest headspace length on my multiple chambers 6BRs and 6PPCs. When needing a longer headspace, I just refer to my notes and add the appropriate shim under the lock ring. Keep it simple.” — F.D. Shuster
Mats Johansson writes: “I’ve been using [shims] since Skip Otto (of BR fame) came out with them. I set up my dies with the .006″ shim, giving me the option of bumping the shoulder a bit more when the brass gets old and hardens while still having room to adjust up for zero headspace, should I have missed the original setup by a thou or two. Hunting rounds can easily be bumped an extra .002-.003″ for positive, no-crush feeding. Being a safety-oriented cheapskate, I couldn’t live without them — they let me reload my cases a gazillion times without dangerous web-stretching. Shims are a must-have, as simple as that.” — Mats Johansson
Sinclair Int’l offers a seven-piece set of Sizing Die Shims that let you adjust the height of your die (and thereby the amount of bump and sizing) in precise .001″ increments. Sinclair explains: “Some handloaders will set their die up to achieve maximum sizing and then progressively use Sinclair Die Shims between the lock ring and the press head to move the die away from the shellholder. Doing this allows you to leave the lock ring in the same position. These shims are usually available in increments of .001″ and work very well.”
Seven Shims from .003″ to .010″
Sinclair’s $12.49 Die Shim Kit (item 22400) includes seven shims in thicknesses of .003, .004, .005, .006, .007, .008, and .010. For ease of use, shim thickness is indicated by the number of notches cut in the outer edge of each shim. Even without looking you can “count” the notches by feel.
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The ANSI / SAAMI group, short for “American National Standard Institute” and “Sporting Arms and Ammunition Manufacturers’ Institute”, have made available some time back the voluntary industry performance standards for pressure and velocity of centerfire rifle sporting ammunition for the use of commercial manufacturers. [These standards for] individual cartridges [include] the velocity on the basis of the nominal mean velocity from each, the maximum average pressure (MAP) for each, and cartridge and chamber drawings with dimensions included. The cartridge drawings can be seen by searching the internet and using the phrase ‘308 SAAMI’ will get you the .308 Winchester in PDF form. What I really wanted to discuss today was the differences between the two accepted methods of obtaining pressure listings. The Pounds per Square Inch (PSI) and the older Copper Units of Pressure (CUP) version can both be found in the PDF pamphlet.
CUP Pressure Measurement
The CUP system uses a copper crush cylinder which is compressed by a piston fitted to a piston hole into the chamber of the test barrel. Pressure generated by the burning propellant causes the piston to move and compress the copper cylinder. This will give it a specific measurable size that can be compared to a set standard. At right is a photo of a case that was used in this method and you can see the ring left by the piston hole.
PSI Pressure Measurement
What the book lists as the preferred method is the PSI (pounds per square inch or, more accurately, pound-force per square inch) version using a piezoelectric transducer system with the transducer flush mounted in the chamber of the test barrel. Pressure developed by the burning propellant pushes on the transducer through the case wall causing it to deflect and make a measurable electric charge.
Q: Is there a standardized correlation or mathematical conversion ratio between CUP and PSI values?
Mahin: As far as I can tell (and anyone else can tell me) … there is no [standard conversion ratio or] correlation between them. An example of this is the .223 Remington cartridge that lists a MAP of 52,000 CUP / 55,000 PSI but a .308 Winchester lists a 52,000 CUP / 62,000 PSI and a 30-30 lists a 38,000 CUP / 42,000 PSI. It leaves me scratching my head also but it is what it is. The two different methods will show up in listed powder data[.]
So the question on most of your minds is what does my favorite pet load give for pressure? The truth is the only way to know for sure is to get the specialized equipment and test your own components but this is going to be way out of reach for the average shooter, myself included. The reality is that as long as you are using printed data and working up from a safe start load within it, you should be under the listed MAP and have no reason for concern. Being specific in your components and going to the load data representing the bullet from a specific cartridge will help get you safe accuracy. [With a .308 Winchester] if you are to use the 1% rule and work up [from a starting load] in 0.4 grain increments, you should be able to find an accuracy load that will suit your needs without seeing pressure signs doing it. This is a key to component longevity and is the same thing we advise [via our customer service lines] every day. Till next time, be safe and enjoy your shooting.
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Each Wednesday, the U.S. Army Marksmanship Unit publishes a reloading “how-to” article on the USAMU Facebook page. This week’s “Handloading Hump Day” post covers an important safety issue — why you should never assume that a stated “book” load for a particular bullet will be safe with an equal-weight bullet of different shape/design. The shape and bearing surface of the bullet will affect the pressure generated inside the barrel. Visit the USAMU Facebook page next Wednesday for the next installment.
Beginning Handloading, Part 13:
Extrapolating Beyond Your Data, or … “I Don’t Know, What I Don’t Know!”
Last week, we addressed several key facets of Service Rifle reloading. Today, we continue our Handloading Safety theme, focusing on not inadvertently exceeding the boundaries of known, safe data. Bullet manufacturers’ loading manuals often display three, four, or more similar-weight bullets grouped together with one set of load recipes. The manufacturer has tested these bullets and developed safe data for that group. However, seeing data in this format can tempt loaders — especially new ones — to think that ALL bullets of a given weight and caliber can interchangeably use the same load data. Actually, not so much.
The researchers ensure their data is safe with the bullet yielding the highest pressure. Thus, all others in that group should produce equal or less pressure, and they are safe using this data.
However, bullet designs include many variables such as different bearing surface lengths, hardness, and even slight variations in diameter. These can occasionally range up to 0.001” by design. Thus, choosing untested bullets of the same weight and caliber, and using them with data not developed for them can yield excess pressures.
This is only one of the countless reasons not to begin at or very near the highest pressure loads during load development. Always begin at the starting load and look for pressure signs as one increases powder charges.
Bullet bearing surface length (BSL) is often overlooked when considering maximum safe powder charges and pressures. In photo 1 (below), note the differences in the bullets’ appearance. All three are 7mm, and their maximum weight difference is just five grains. Yet, the traditional round nose, flat base design on the left appears to have much more BSL than the sleeker match bullets. All things being equal, based on appearance, the RN/FB bullet seems likely to reach maximum pressure with significantly less powder than the other two designs.
Photo 1: Three Near-Equal-Weight 7mm Bullets with Different Shapes
Due to time constraints, the writer used an approximate, direct measurement approach to assess the bullets’ different BSLs. While fairly repeatable, the results were far from ballistics engineer-grade. Still, they are adequate for this example.
Bullet 1 (L-R), the RN/FB, has a very slight taper and only reaches its full diameter (0.284”) very near the cannelure. This taper is often seen on similar bullets — it helps reduce pressures with good accuracy. The calculated BSL of Bullet 1 was ~0.324”. The BSL of Bullet 2, in the center, was ~0.430”, and Bullet 3’s was ~ 0.463”. Obviously, bullets can be visually deceiving as to BSL!
Some might be tempted to use a bullet ogive comparator (or two) to measure bullets’ true BSL for comparison’s sake. Unfortunately, comparators don’t typically measure maximum bullet diameter and this approach can be deceiving.
Photo 2: The Perils of Measuring Bearing Surface Length with Comparators
In Photo 2, two 7mm comparators have been installed on a dial caliper in an attempt to measure BSL. Using this approach, the BSLs differed sharply from the original [measurements]. The comparator-measured Bullet 1 BSL was 0.694” vs. 0.324” (original), Bullet 2 was 0.601” (comparator) vs. 0.430” (original), and Bullet 3 (shown in Photo 2) was 0.602” (comparator) vs. 0.463” (original). [Editor’s comment — Note the very large difference for Bullet 1, masking the fact that the true full diameter on this bullet starts very far back.]
Please join us again next week as we examine other lesser-discussed variables that affect pressure and velocity during handload development. In the meantime, stay safe, and favor center!
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German Salazar has written a very thorough guide to measuring nearly all the critical dimensions of cartridge brass. In his Measuring the Case article, on his Rifleman’s Journal website, German reviews the tools and techniques required to measure everything from case overall length to case neck concentricity. Step-by-step, German shows how to measure: Case Length, Case Body length (below neck), Neck Diameter, Headspace, Base Diameter, Neck Thickness, and Case Neck Concentricity.
If you are an “advanced reloader” or want to be, you should read German’s article. Not only does German explain the most common measuring procedures, he highlights some alternative methods you might not have tried yet. The article also links to related discussions of more complex measurement tasts, such as determining case body wall thickness variation.
Even if you’re not a competitive shooter, measuring your brass can provide important safety benefits. As German explains in the conclusion of his article: “There are obviously a lot of measurements that can be taken on the cartridge case and in some cases, more than one way to take them. However, the first two that any new reloader must learn are case length and neck clearance, these two are safety concerns and if overlooked can results in serious damage to the rifle and injury to you.”
Each Wednesday, the U.S. Army Marksmanship Unit publishes a reloading “how-to” article on the USAMU Facebook page. This USAMU “Handloading Hump Day” article, the second in a series on improving concentricity, has many useful tips. If you use standard (non-micrometer) seating dies when loading some cartridge types, this article is worth reading. And visit the USAMU Facebook page next Wednesday for the next installment.
Once again, it’s time for USAMU’s “Handloading Hump-Day!” Last week, we addressed achieving very good loaded-cartridge concentricity (AKA “TIR”, or Total Indicator Runout) using standard, “hunting grade” reloading dies.
We explained how to set up the Full-Length Size die to float slightly when correctly adjusted for desired case headspace. We also cited a study in which this method loaded ammunition straighter than a set of [higher grade] match dies from the same maker. [One of the keys to reducing TIR with both sets of dies was using a rubber O-ring below the locking ring to allow the die to float slightly. READ Full-Length Sizing Die TIP HERE.]
Now, we’ll set up a standard seating die to minimize TIR — the other half of the two-die equation. As before, we’ll use a single-stage press since most new handloaders will have one. A high-quality runout gauge is essential for obtaining consistent, accurate results.
Having sized, primed and charged our brass, the next step is bullet seating. Many approaches are possible; one that works well follows. When setting up a standard seating die, insert a sized, trimmed case into the shell-holder and fully raise the press ram. Next, back the seating stem out and screw the die down until the internal crimping shoulder touches the case mouth.
Back the die out one-quarter turn from this setting to prevent cartridge crimping. Next, lower the press ram and remove the case. Place a piece of flat steel on the shellholder and carefully raise the ram. Place tension on the die bottom with the flat steel on the shellholder. This helps center the die in the press threads. Check this by gently moving the die until it is well-centered. Keeping light tension on the die via the press ram, secure the die lock ring.
If one were using a micrometer-type seating die, the next step would be simple: run a charged case with bullet on top into the die and screw the seating stem down to obtain correct cartridge OAL.
However, with standard dies, an additional step can be helpful. When the die has a loosely-threaded seating stem, set the correct seating depth but don’t tighten the stem’s lock nut. Leave a loaded cartridge fully raised into the die to center the seating stem. Then, secure the stem’s lock nut. Next, load sample cartridges and check them to verify good concentricity.
One can also experiment with variations such as letting the seating stem float slightly in the die to self-center, while keeping correct OAL. The runout gauge will show any effects of changes upon concentricity. However, the first method has produced excellent, practical results as evidenced by the experiment cited previously. These results (TIR Study 2) will reproduced below for the reader’s convenience.
TIR Study 2: Standard vs. Match Seating Dies
50 rds of .308 Match Ammo loaded using carefully-adjusted standard dies, vs. 50 using expensive “Match” dies from the same maker.
Standard dies, TIR:
0.000” — 0.001” = 52%;
0.001”– 0.002” = 40%;
0.002”– 0.003” = 8%. None greater than 0.003”.
AccurateShooter Comment: This shows that, with careful adjustment, the cheaper, standard dies achieved results that were as good (or better) than the more expensive “Match” Dies.
These tips are intended to help shooters obtain the best results from inexpensive, standard loading dies. Especially when using cases previously fired in a concentric chamber, as was done above, top-quality match dies and brass can easily yield ammo with virtually *no* runout, given careful handloading.
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Ever wondered what caused a particular bulge or marking on a case? And more importantly, does the issue make the case unsafe for further use? Sierra Bullets Ballistic Technician Duane Siercks offers some insight into various issues and their causes in this article from the Sierra Blog.
Diagnosing Problems with Cartridge Brass
by Duane Siercks, Sierra Bullets
I was handed a small sample of .223 Rem cases the other day and was asked if I could comment on some marks and appearances that had been noticed as they were sorting through the cases. I will share what was observed and give you what would seem to be a cause for them. These were from an unknown source, so I have no way of knowing what type of firearm they were fired in or if they were factory loaded or reloaded ammunition.
Example ONE: Lake City 5.56, Unknown Year
Case #1 was seen to have a very rounded shoulder and split. Upon first look it was obvious that this round had been a victim of excess pressure. The firearm (perhaps an AR?) was apparently not in full battery, or there was possibly a headspace issue also. While taking a closer look, the primer was very flat and the outside radius of the primer cup had been lost. High pressure! Then I also noticed that there was an ejector mark on the case rim. This is most certainly an incident of excessive pressure. This case is ruined and should be discarded. See photo below.
Example TWO: Lake City Match 1993
Case #2 appears very normal. There was some question about marks seen on the primer. The primer is not overly flattened and is typical for a safe maximum load. There is a small amount of cratering seen here. This can be caused by a couple of situations.
Cratering is often referred to as a sign of excess pressure. With safety in mind, this is probably something that should make one stop and really assess the situation. Being as there are no other signs of pressure seen with this case, I doubt that pressure was unsafe. That leads us to the next possibility. This can also be caused by the firing-pin hole in the bolt-face being a bit larger than the firing-pin, and allowing the primer to flow back into the firing-pin hole causing the crater seen here. This can happen even with less-than-max pressures, in fact it has been noted even at starting loads. Always question whether pressure is involved when you see a crater. In this situation, I lean toward a large firing-pin hole. This case should be safe to reload.
Example THREE: R-P .223 Remington
Case #3 appears normal with one exception. There are two rings seen about one half inch below the base of the shoulder. These rings are around the circumference of the case, one being quite pronounced, and the other being noticeably less.
As we do not know the origin of the firearm in which this case was fired, it does seem apparent that the chamber of the firearm possibly had a slight defect. It could have been that the reamer was damaged during the cutting of this chamber. I would suggest that the chamber did have a couple of grooves that imprinted onto the case upon firing. This firearm, while maybe not dangerous should be looked at by a competent gunsmith. In all likelihood, this case is still safe to use.
Example FOUR: R-P .223 Remington
Case #4 has no signs of excess pressure. There is a bulge in the case just ahead of the case head that some might be alarmed by. This bulge is more than likely caused by this case being fired in a firearm that had a chamber on the maximum side of S.A.A.M.I. specifications. There is actually no real issue with the case. Note that the primer would indicate this load was relatively mild on pressure.
If this case was reloaded and used in the same firearm numerous times there might be a concern about case head separation. If you were going to use this case to load in an AR, be sure to completely full-length re-size to avoid chambering difficulties. This case would be safe to reload.
CLICK HERE for MORE .223 Rem Case Examples in Sierra Blog
It is very important to observe and inspect your cases before each reloading. After awhile it becomes second nature to notice the little things. Never get complacent as you become more familiar with the reloading process. If ever in doubt, call Sierra’s Techs at 1-800-223-8799.
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Harrell’s Precision sells “semi-custom” full-length bushing dies for the PPC and 6BR chamberings. While the Harrell brothers do not cut the die to spec, they carry a large selection of dies made with slightly different internal dimensions. When you send in your fired brass, the Harrells choose a die from inventory with just the right amount of sizing (diameter reduction) at the top and bottom of the case. Given the quality, and precise fit, Harrell’s full-length dies are a good value at $70.00 plus shipping.
Bump Measuring Collar
The Harrell brothers provide a nice bonus item with each full-length die — a neat, little shoulder bump measuring device as shown in the photo at right. Hornady/Stoney Point sells a stand-alone tool that does the same job, but the Harrell’s bump collar is simpler and faster. To measure your shoulder bump, simply place the Harrell’s bump collar over the front of your deprimed case (before sizing) and measure the OAL with your calipers. Then size the case in your full-length die, replace the collar and repeat the measurement. You want to set your die so the shoulder moves back about .001″ to .0015″ for most applications. (With semi-auto guns you may want more bump.)
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Each Wednesday, the U.S. Army Marksmanship Unit (USAMU) publishes a reloading “how-to” article on the USAMU Facebook page. In this article, the USAMU’s reloading gurus address a question frequently asked by prospective handloaders: “Should I buy a single-stage press, or a progressive?” The USAMU says the best answer is Solomon-esque in both its wisdom and simplicity: “Get BOTH!” However, there is definitely more to the issue, as the USAMU explains below.
Progressive Press Safety Considerationsby USAMU Staff
Many are the beginning handloaders who have asked a friend about their “setting up” a progressive press for them. The idea is that the newbie could then just feed in components and crank out buckets of practice ammo without needing to really learn much about handloading. Tempting though this might be, that’s simply not how it works. Such an approach might be ok if there were never a malfunction with either press or operator, but that’s unrealistic. Our hypothetical newbie would then lack the knowledge to problem-solve most situations.
Forum member Rich DeSimone uses a handy “Stub Gauge” for setting shoulder “bump” and seating depth. The gauge is made from a section of barrel lopped off when the muzzle is crowned. The chambering reamer is run in about 1/4 of the way, enough to capture the neck and shoulder area of the case. Rich then uses his full-length die to “bump” a master case with the ideal amount of headspace for easy feeding and extraction. He takes that case and sets it in this Stub Gauge, and measures from the front of the gauge to the rim. He can then quickly compare any fired case to a his “master” case with optimal headspace. Since the gauge measures off the shoulder datum, this tells him how much to bump his fired brass.
In addition, the Stub Gauge can be used to set bullet seating-depth. Rich has a channel cut transversely on one side of the gauge, exposing the throat area. Since the interior of the gauge is identical to the chamber in his gun, this lets him see where a seated bullet engages the rifling. He can tinker with bullet seating length until he gets just the right amount of land contact on the bullet, confirmed visually. Then he measures the case OAL and sets his seating dies accordingly. This is much handier than using a Stoney Point Tool to measure distance to the lands. As your barrel’s throat wears, you may seat your bullets out further to “chase the lands”, but the gauge provides a constant land engagement point, in the barrel’s “as new” condition. By measuring the difference between the land contact point on the gauge and the actual contact point on your barrel, you can determine throat “migration”.
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Western Powders (which sells Accurate, Ramshot, and Norma powders) has published an article on case inspection and preparation. There are many tips in this article that can be useful to precision hand-loaders. For example, every time you open a new box of cartridge brass (particularly from domestic makers), you should inspect each case for flaws.
TIP ONE: Visual Inspection — Finding Flaws
Cases are mass-produced items and malformed ones are relatively common. Inspect each case carefully looking for obvious defects. A bench-mounted magnifying glass with light is a real help for the over-40 crowd. The main defects will be cracks in the neck or case body, crushed shoulders or deep creases in the neck. Next check the primer pocket. It is also fairly common to find flash holes that are damaged or, more rarely, not concentric to the primer pocket.
Imperfections like small dings in the case body, or necks that are not completely symmetrical do not have to be eliminated at this step. Damage of this sort is usually from loose packaging and usually has not seriously damaged the brass. [Running an expander mandrel in the neck] and fire-forming will iron out these largely cosmetic issues.
AccurateShooter.com has released the most complete discussion of the 6.5×47 Lapua cartridge ever published. Our new 6.5×47 Cartridge Guide is packed with information. If you own a 6.5×47 rifle, or are thinking of building a rifle with this chambering, definitely read this Cartridge Guide from start to finish. Our comprehensive, 5000-word article was researched and written by the 6.5 Guys, Ed Mobley and Steve Lawrence. Both Ed and Steve shoot the 6.5×47 Lapua in competition and they are experts on this accurate and efficient mid-sized cartridge.
You’ll find everything you need to know about the 6.5×47 Lapua in our new Cartridge Guide. We cover ballistics, reloading, die selection, and we provide an extensive list of recommended loads, for bullets from 120 to 140 grains. You can read interviews with respected experts who’ve built and tested many 6.5×47 rifles. The Guide includes helpful tech tips such as how to maximize the powder fill in your cases. This Cartridge Guide can put you on the “fast track” — helping you develop accurate, reliable loads with minimal development time.
6.5×47 Lapua Cartridge Guide Highlights:
Comprehensive Load Data
Best Bullets and Primers for 6.5×47
Ballistics Comparison Charts
Sizing and Seating Die Options
6mm-6.5×47 (Necked-Down) Options
Ask the Experts Section
Tips for Accurate Reloading
Brass Life and Annealing
Chambering and Gunsmithing Tips
6.5×47 Lapua for Hunting
6.5×47 Lapua for Tactical Competition
6.5×47 Factory-Loaded Ammo
Here is a sample from the 6.5×47 Cartridge Guide’s Ask the Experts Section. This is an interview with Rich Emmons, one of the founders of the Precision Rifle Series:
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This week, the U.S. Army Marksmanship Unit is pleased to host pistol teams from the various U.S. Armed Services in the 56th Annual Interservice Pistol Championship. Our Handloading Shop members have enjoyed discussing pistol accuracy and enjoying the camaraderie of competitive shooters from all over. In that spirit, this week’s topic will focus on handloading for best pistol accuracy, rather than our usual rifle-oriented information.
Optimize the Taper Crimp
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of crimp and its effect on accuracy. Different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors. It is not unusual for our Shop to vary a load’s crimp in degrees of 0.001″ and re-test for finest accuracy.
Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
The last half-inch or so of your barrel is absolutely critical. Any damage (or abnormal wear) near the crown will cause a significant drop-off in accuracy. Here are ways you can check the end of your barrel, using a common Q-Tip.
Use Q-Tip for Barrel Inspection
To find out if you have a burr or damage to your crown, you can use an ordinary Q-tip cotton swab. Check the edges of the crown by pulling the Q-tip gently out past the edge of the crown. If you have a burr, it will “grab” the cotton and leave strands behind.
Larry Willis has another way to use a Q-Tip: “Here’s a neat trick that will surprise you with how well it works.” Just insert a Q-Tip into your barrel (like the picture below), and it will reflect enough light so that you can get a real good look at the last half inch of rifling and the crown of your barrel. In most cases you’ll find that this works much better than a flashlight. Larry tells us: “I’ve used this method about a jillion times. Q-Tips are handy to keep in your cleaning supplies anyway. This is a good way to judge approximately how well you are cleaning your barrel when you’re at the range. It’s also the best way to examine your barrel when you’re in the field.”
The $52.99 RCBS Precision MIC is a well-made and useful tool for measuring cartridge headspace and bullet seating depth. The Precision Mic measures from a datum point on the case shoulder to the base. Unfortunately the Precision MIC is not specifically made for the 6mmBR Norma, 22BR, 6XC or 6.5×47 Lapua cases. Don’t despair. Reader Caduceus devised a clever way to adapt a .308 Win Precision Mic for short cases that match the .308 Win in rim diameter and case body diameter. He simply creates a spacer out of a pistol cartridge. He trimmed a 9mm case to 0.511″ and “found this to be a perfect fit which gave a zero micrometer reading when the FL-sized 6BR case was placed in it.” We expect many readers already own a Precision Mic for their .308s. Now you can adapt this tool for the 6BR family of cartridges, for no extra cost. Cut the spacer shorter for the 6.5×47 Lapua and 6-6.5×47 cartridges.
How to Use the Precision Mic with a Spacer
Caduceus explains: “I can use the .308 version of the RCBS Precision Mic to compare brass which has been fully sized in my 6BR body die with brass which has been fired in my chamber. With the spacer inserted, FL-resized cases mic 0.000″ at the datum point on the shoulder. Using the same set-up, fire-formed cases measure +0.005″. In other words, my chamber has a headspace of +0.005″ above minimum dimensions. This is fairly typical of a custom rifle set up for switch-barrel use. If I were to FL-resize my brass down to minimum spec each time, this excessive working would shorten its life-cycle and might lead to case head separation. Now that I know the headspace of the chamber, I can substitute the standard shell holder on my press with a Redding +0.004″ competition shell-holder. This ensures that my cases only receive 0.001″ of shoulder set-back.”
Click HERE for a full article explaining how to adapt an RCBS Precision Mic for use with a 6BR. You can do the same thing with a 6XC or 6.5×47 case–just cut the spacer to a shorter length (for an 0.000″ mic reading). Note: You can also use this procedure with an RCBS .243 Winchester Precision Mic.
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When you look at a loading manual with load data, you will usually see pressure ratings for stated load. Sometimes these are listed in PSI numbers, which most people correctly understand to be Pounds per Square Inch of pressure. However, powder-makers also commonly list pressure in CUP numbers. CUP stands for Copper Unit of Pressure. You may be asking — “What exactly is a CUP, and what is the origin of that unit of measurement?” You may also be wondering — “What’s the difference between CUP pressures and PSI pressures?” On Hodgdon’s Facebook Page, you’ll find answers to these questions.
Q: What is CUP?
A: Copper Unit of Pressure (CUP) is a measurement used in the ammunition industry to determine the chamber pressure created by a cartridge load. Originally, a precisely formed copper slug was placed in a fixture over the chamber. When the cartridge was fired, the amount of crushing measured on the slug allowed engineers to determine the pressure.
These days, modern electronic transducers provide faster, more accurate measurements of chamber pressures in pounds per square inch (PSI). CUP and PSI are measured to different scales and are NOT interchangeable.
Hodgdon Reloading Data Center Sample
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Gear Reviewby Germán A. Salazar, Contributing Editor
Reloading at the range with an arbor press and Wilson dies is my preferred method of load development. I’ve had a chance to test and evaluate the Arbor Press from 21st Century Shooting. I have to say I’m very favorably impressed by it.
An arbor press’ basic function is simple enough: exert sufficient downward pressure on the die to either size the case neck or seat the bullet depending on which die is in use. It isn’t a mechanically challenging function. So why do we use an arbor press and what should be look for in one? Consistent operation, sensitive feel, quality of design and machining are the hallmarks of a good arbor press and this one from 21st Century comes away with good marks in all areas.
For my initial session with the press, I seated 72 bullets in .30-06 cases, another 70 in .308 cases and neck sized a handful of cases (just for evaluation since I prefer to full-length size). The design of the actuating arm, which angles slightly away from the press was very convenient, allowing me to operate it with less jostling of the press because my fingers weren’t bumping into the press head as they sometimes do with my previous press that has the handle parallel to the press head. That’s a nice touch and shows the press was designed by someone who has used these things.
The press uses a relatively light return spring which materially aids the feel of seating pressure. I prefer this to a heavier return spring which would reduce the feel that I really look for in an arbor press. For someone who uses very heavy neck tension this might not be a big concern, but because I usually use 0.001″ to 0.002″ neck tension, the ability to detect small levels of variance in seating pressure is important to me.
High Quality Machining and Parts Finishing
Every part of the 21st Century press reflects careful thought and skilled machining. The knurled wheel for adjusting the height of the press head is a distinct improvement over the plastic hardware store knobs seen on many presses.
The aluminum press head itself is nicely anodized, the steel base well blued and the shaft nicely polished. Even the decapping base (photo at left) reflects careful design as well as precise machining. Overall, the press gives a look and feel of quality and is a welcome addition to my range reloading setup.
Editors’ Note: The designer of the 21st Century Arbor Press has decades of tool-making experience, and he has designed tools for many “big-name” companies. 21st Century stands behind the product with a lifetime warranty for the original purchaser. The Arbor Press is currently offered in four different versions, with two post heights (8.5″ or 10.5″), and two baseplate sizes (small 3″ x 4″ or large 4″ x 5″). Prices start at $94.99 for the 8.5″ post and small baseplate. CLICK HERE for more info.
In this video, Forum member Erik Cortina shows how to create a custom modified case for use with the Hornady Lock-N-Load Overall Length Gauge (formerly the Stoney Point Tool). While Hornady sells modified cases for many standard cartridges, if you shoot a wildcat such as the 6mm Dasher or .284 Shehane, you’ll need to create a custom modified case*. And even if you shoot a standard cartridge such as the .308 Winchester you can get more consistent measurements if you make a custom modified case from a piece of brass fired in your chamber.
The process is straight-forward. Take a piece of brass fired in your chamber and full-length size it (with about .002″ shoulder bump). Then you need to drill out the primer pocket. Erik uses a mini-lathe for the operation, but this general process can be done with a drill press or other tools. Erik shows how to do this with a 0.290″ HSS (High Speed Steel) drill bit on a mini-lathe. After drilling the hole comes the tricky part — you need to tap the case with the precise 5/16″ x 36 threads per inch (tpi) right-hand thread that matches the male thread on the O.A.L. Gauge. This 5/16″ x 36 tpi tap is pretty uncommon, but you can order it from Amazon.com if you can’t source it locally.
If you use a mini-lathe, Erik suggests loosening the tailstock slightly, so it can float while cutting the threads. Erik also says: “Make sure you get the tap on pretty tight — it’s going to want to spin.” Erik turns the case at about 100 rpm when tapping the threads. Once the case and tap are rigged, the actual tapping process (see video at 6:00) takes only a few seconds. While the mini-lathe makes the tapping process go more quickly, the threading can also be done with other systems.
TIP: Don’t just make one modified case, make three. That gives you one for your range kit, one for your home reloading bench, plus a spare (since you WILL eventually lose or misplace one).
Here’s the Stuff You Need
5/16″-36 TPI Threading Tap
The required thread is somewhat uncommon. You need a 5/16″ – 36 tpi Right Hand Thread Tap. If you can’t find it locally, Amazon.com carries the correct tap. Erik notes: “The 5/16-36 tpi tap is not a common size. I think Hornady did this on purpose to make it more difficult for the average guy to make his own modified cases.”
0.290″ Drill Bit
Erik uses an 0.290″ HSS “L” drill bit. (This “L” Letter Gauge code designates a 0.290″ diameter bit). A close metric equivalent would be 7.3 mm (0.286″). Erik says: “A 9/32″ drill will also work but it will be harder to run the tap in since the hole will be .281″ instead of .290″ with the Letter Gauge L bit.”
Tips for Using O.A.L. Gauge with Modified Case
We’ve noticed that many folks have trouble getting reliable, consistent results when they first start using the Hornady O.A.L. Gauge (formerly the Stoney Point Tool). We’ve found this is usually because they don’t seat the modified case properly and because they don’t use a gentle, consistent method of advancing the bullet until it just kisses the lands.
Here is our suggested procedure for use the O.A.L. Gauge. Following this method we can typically make three of four measurements (with the same bullet), all within .001″ to .0015″. (Yes, we always measure multiple times.)
1. Clean your chamber so there is no build-up of carbon, debris, or lube. Pay particular attention to the shoulder area.
2. Screw the modified case on to the O.A.L. Gauge. Make sure it is seated firmly (and doesn’t spin loose). Note, you may have to re-tighten the modified case after insertion in the chamber.
3. Place your selected bullet so that the ogive (max bullet diameter) is behind the case mouth. This prevents the bullet from “snagging” as you insert the tool in the action.
4. Insert the O.A.L. Gauge into your chamber smoothly. Push a little until you feel resistance. IMPORTANT — You need to ensure that the shoulder of the modified case is seated firmly against the front of your chamber. You may have to wiggle and twist the tool slightly. If you do not have the modified case seated all the way in, you will NOT get a valid measurement.
5. Advance the bullet slowly. (NOTE: This is the most important aspect for consistency!). Push the rod of the O.A.L. tool gently towards the chamber. DON’T shove it hard! Easy does it. Stop when you feel resistance.
6. IMPORTANT. After gently pushing on the rod, give the end of the rod a couple forward taps with your finger. If your bullet was slightly skewed, it may have stopped too far back. Adding a couple extra taps will fix that. If the bullet moves after the taps, then again push gently on the rod. NOT too much! You just want to push the bullet until it just “kisses” the lands and then stops. Do NOT jam the bullet into the rifling. If you do that you will never get consistent results from one measurement to the next.
* For a $15.00 fee, Hornady will make a custom modified case for you if you send two fired pieces of brass. Send fired cases and $15.00 check to: Hornady Manufacturing, Attn: Modified Cases, 108 S. Apollo St., Alda, NE 68810. More Info HERE.
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Sinclair International has created a series of instructional videos illustrating the basics of metallic cartridge reloading. The 8-part series starts with reloading basics and provides step-by-step, how-to instructions that will help new reloaders get started. Detailed, animated illustrations show you what happens inside the chamber when shooting, and inside the dies during each step of reloading. The videos can be viewed on Sinclair Int’l’s YouTube page. Shown below is the first video in the series:
Each of the eight videos is hosted by Sinclair Int’l President Bill Gravatt. Bill doesn’t just show you “how”, he tells you “why”. The how-to segments cover case inspection, proper die set up, case sizing, primer installation, powder measuring, bullet seating, crimping, and even goes into the record keeping needed for the handloader. “We wanted to give shooters who haven’t reloaded a look at all the advantages of creating your own ammo and how easy it is to get started,” said Gravatt, “without telling them they had to have any certain brand or type of equipment to do the job.” The eight videos are:
Part 1 — Intro to Video Series
Part 2 — Intro to Reloading Safety
Part 3 — Metallic Cartridge Components
Part 4 — The Firing Sequence
Part 5 — Tools for Reloading
Part 6 — Loading Bottle-Neck Cartridges
Part 7 — Loading Straight Wall Cartridges
Part 8 — Reloading Series Conclusion
Shown below is Part 5 of the video series, covering the tools used for precision reloading.
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When Berry’s Bench Topper was first released a couple years ago, it proved very popular with hand-loaders looking for extra space on their bench. This unique all-metal riser lets you place a reloading press above your bench surface, clearing valuable space. Unfortunately, after the initial run of Bench Toppers sold out, this product have been nearly impossible to find. But now the Bench Topper is back…
We’re pleased to report that the Bench Topper is back in production. The Bench Topper, from Berry’s Manufacturing, is a sturdy platform that holds a loading press and storage bins in a raised position above your bench — effectively creating additional room for scales, trimmers, and component storage below. The $111.30 Bench Topper (Midsouth item 037-00191) can bolted to your bench, or it can be secured with C-Clamps (for easy removal). Do you load at the range? The Bench Topper can be easily transported in your vehicle, providing a handy platform for your press and powder measure.
Berry’s Bench Topper is crafted from CNC-machined aluminum and powder-coated silver for durability. It comes with two aluminum hangers for storage bins for bullets or brass. All fasteners are recessed for a clean work surface. NOTE: The Bench Topper must be assembled by the purchaser, and YOU MUST DRILL YOUR OWN HOLES for installation of your press or other hardware. This requires a few minutes of initial set-up time, but this allows a secure, custom installation for any brand of reloading press. CLICK HERE for Bench Topper Assembly Instructions (PDF file).
Bench Topper Specs:
6 x 20 x 1/4″
10 x 20 x 1/4″
Height: 11.5 Inches
Weight: 12.5 Pounds
Product Tip from EdLongrange. We welcome user submissions.
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