5.56x45 Reference Rounds LC 69

Hello all, I recently came across a few boxes of this and was wondering if anyone can add more details on what this type of ammunition was used for, other than what is written in HWS III, which was only two paragraphs. As always, many thanks to this community! V/r Henry

Reference ammunition is loaded to very close tolerances and used for calibrating pressure barrels. Each lot is “assessed”, that means its gas pressure measured in different, carefully controlled equipment. For example, a lot may be assessed as 50000 psi.

Simplified example of use: Manufacturer XYZ may have tested his new product and obtained 51500 psi in his own pressure barrel.
Now he tests some approved reference cartridges in the same pressure barrel. Let us assume, he measures 49000 psi. That means 1000 psi less than the “assessed” 50000 psi.

Now back to his own product. The -1000 psi difference from the reference lot is also applied to the measured pressure of the XYZ product: 51500-1000 = 50500 psi. This “corrected” pressure is then cosidered to be a sort of “real” pressure of XYZ’s product.

Reference lots are used to compensate for the unavoidable differences of ballistic measuring equipment and make measurement results comparable.

1 Like

Thank you sir for that explanation, makes total sense they way you describe it! V/r Henry.

Reference 5.56 mm cartridge lots are also loaded using reference powder lots. Average velocity is indicated as 3165 +/- 20 fps at 78 feet, sd ≤ 25 fps versus 3250 +/- 40 fps at 15 feet, sd 40 fps max of the M193.

Here is the military specification: 1985 - MIL-C-46397C - Cartridge, 5.56mm, Reference.pdf (2.4 MB)

Regards,

Fede

1 Like

Good stuff Fede, thank you sir!!