B.L.U.F.
An introduction to how to mess up big time when reloading. Remember, don’t trust me. Read the instructions in your reloading guides, your press and die instructions. Follow their instructions.
(2400 words)
The wonderful thing about reloading is the amount of control you can get over the process of creating the “perfect” load for your firearm. The negative thing about reloading is that a mistake can send you to the hospital, or worse, the morgue.
Every “regular” cartridge has a SAAMI specification for it. The SAAMI specification includes the dimensions of the chamber and the pressures for each cartridge. The SAAMI specifications also include how to perform tests.
In general, we do not have the equipment to perform the tests that would give us objective insight into what our loads are doing. Everything we have to work with is measured after the bullet leaves the barrel. This includes velocity, grouping, and other objective measurements of the results of our load.
Unfortunately, there are many aspects of the reloading process that can change velocity or groupings.
What we cannot measure is the pressure inside the chamber. This is the critical measurement.
COPPER CRUSHER SYSTEM
This system employs a copper crusher cylinder that is compressed by a piston fitted to a piston hole into the chamber of the test barrel. The pressure developed by the gases from the burning propellant acts through the piston hole, allowing the gases to force the piston upward, and thereby permanently compressing the copper crusher cylinder. The Sporting Arms and Ammunition Manufacturers’ Institute has adopted the pressure units designation of “Copper Units of Pressure” (abbreviated CUP) for this system. This designation applies only to values obtained using the particular crushers, tarage tables and methods outlined in this Standard.
—Z299.4 (SAAMI Dec. 2015)
Here are a few of the pressure measurements from the SAAMI specifications.
Cartridge |
Max. Avg. Pres. MAP |
7.62×39 |
500 |
8 mm Mauser |
370 |
223 Remington |
520 |
30 Carbine |
400 |
30-06 |
500 |
30-30 Win. |
380 |
When we purchase a “modern” firearm, we are told that the firearm can safely chamber and fire rounds that meet SAAMI specifications. In the US, that is done by manufacturers not wanting to be sued.
When the gun banners scream about “only gun manufactures are protected from being sued”, they are lying. If you purchase a modern firearm and use only reputable ammunition, and that firearm “explodes”, the manufacturer can be sued. And rightly so.
In other countries, they go a bit further.
Proofing
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