Correctness Formula – Ultimate Reloader

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I recently pushed the limits of .308 Winchester using Alpha Munitions OCD brass. Details of the brass, reloading process, and the rifle’s chamber all have to come together perfectly for safe, proper firing. Here’s how it works! 

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High Performance Loads and SAAMI Specs

If you’ve been reloading for any length of time, you’ve likely encountered high performance loads. Pushing the performance of the rifle and ammunition can lead to a number of problems, including clickers, poor extraction, high pressure signs, case head separations, and in the worst case scenario, blowing up an action.

A “clicker” refers to the clicking sound when a bolt “lets go” while extracting a semi-stuck case. It hits a hard stop for bolt opening at the top of the extraction ramp. This occurs when there’s an interference fit between the fired case and the chamber wall at base/opening, caused by improper sizing, weak brass or overpressure loads, and incorrect chamber dimensions.  SAAMI exists to standardize chambers and cartridges across the firearms industry for interoperability between ammunition and firearms. They are also a huge resource for reloaders. SAAMI specifies the cartridge dimensions, chamber dimensions, and key tolerances. 

I always consult SAAMI when chambering rifles and use a pin gauge to ensure the chamber isn’t oversized. (An oversized chamber is caused by an off-center reamer.)

Sizing 

Sizing is a significant part of the correctness equation. We have an Area 419 M-Series sizing die.

Area 419 worked closely with companies like Alpha Munitions to understand the sizing process and needs in extreme detail. To optimize the chamber geometry from the SAAMI print, they applied certain offsets, sizing the brass a little below specs and allowing it to spring back very slightly. (Gordy Gritters spoke about designing benchrest dies for certain rifles during his class.)

In short, the sizing die chamber is different from the rifle’s chamber. The desired result is SAAMI specifications for everything except headspace. Area 419’s die is rather unique as it allows the user to dial the shoulder bump/headspace value to a 0.001”.

In talking with Area 419, I learned that a number of dies have oversized base-sizing features and a number of factory rifles have oversized chamber backs.

While this provides greater headroom for improperly sized brass, it’s out of specification, leading to chambering issues with that same brass in other rifles of the same caliber. 

The Optimal Case

Alpha Munitions takes pride in extremely precise, consistent and correct case dimensions with optimized metallurgy and construction.

Their OCD brass, Optimized Case Design with Optimized Case Head Technology, features increased durability of the casings, particularly at the case head. This allowed Bruce Thom and me to complete our .308 high pressure experiment.

Most other brass would have failed before we even observed pressure signs.

Proper Reloading Process

The proper reloading process is also critical including proper equipment and  tools (sizer die and shellholder), proper setup (correct shoulder bump), and annealing. Annealing can extend case life while increasing shoulder bump consistency. 

.308 High Pressure Experiment

DO NOT TRY THIS AT HOME. 

Bruce Thom and I very carefully started with a maximum charge weight of Varget paired with Berger 215 grain Hybrid Target bullets, working our way up to 98% of .300 Win Mag maximum load data.

We were able to achieve this through the correctness formula: correct equipment, correct chamber dimensions, and a quality resizing die. 

Bruce Thom has a lot of experience in this area and we worked directly with Alpha Munitions, who has conducted similar experiments.

We stopped when we observed more serious pressure signs for safety purposes. We observed only slight flattening and slight cratering of primers until almost the very end of the experiment, but no pierced or blown primers. 

Demo

Utilizing our fired brass from the .308 high pressure experiment, we deprimed and resized them using the Area 419 M-Series sizing die on the ZERO press. You will likely feel a bit more sizing than with other dies as the base of the die is sized appropriately for the brass.

0.002″ Shoulder Bump

(For most precision rifles, the appropriate shoulder bump is between 0.001” and  0.002.” Be sure to chamber your ammunition to check for bolt drag before concluding what is best for your gun.)

Next came priming the cases with CCI 400’s using the Primal Rights Competition Primer Seater.

 I trickled 44.0 grains of Varget with the AutoTrickler V4 and seated a Berger .30 caliber 215 Grain Hybrid Target bullet over top.

This is the load that Bruce Thom and I determined to be the safe limit from our testing. 

We had no issues with chambering or extraction with this over-max load. Average velocity was 2,594.5 fps with an SD of 10.0 fps and ES of 24.4 fps.

After firing, the base of one of the cases measured with a micrometer was 0.469”. 

Conclusion

The technology of Alpha Munitions OCD brass truly is something special, particularly when paired with correct chamber geometry and a proper resizing. While not for everyone, this correctness formula is a fantastic way to get the most out of your rifle and ammunition. 

Get the Gear

Alpha Munitions .308 Winchester Small Rifle Primer Brass

BAT Actions

Area 419 M-Series Sizing Dies

Berger .30 Cal 215 Grain Hybrid Target Bullets at Creedmoor Sports and Midsouth Shooters Supply

Hodgdon Varget at Midsouth Shooters Supply

Federal 205 Small Rifle Primers at Midsouth Shooters Supply

CCI No. 400 Small Rifle Primers at Midsouth Shooters Supply

Area 419 ZERO Press at Midsouth Shooters Supply

Area 419 Loading Block at Midsouth Shooters Supply

Primal Rights Competition Primer Seater

Inline Fabrication Ultramount at Midsouth Shooters Supply

A&D FX-120i Precision Balance (CE Products)

AutoTrickler V4

Garmin Xero C1 Pro at Creedmoor Sports and Midsouth Shooters Supply

Leupold Mark 5HD 2-10×30 M1C3 FFP PR1-MOA Riflescope

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Thanks,
Gavin Gear

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