.308 / 7.62 x 51mm IMI Ball Reference Cartridges


#1

Two IMI / Samson .308 Winchester cartons. One has a sticker in English which reads “Reference”, the other has a sticker in Hebrew and I assume these are also reference cartridges. The carton with the sticker in Hebrew contains cartridges headstamped " ⨁ IMI 96 " and the carton with the sticker in English contains cartridges headstamped " ⨁ IMI 95 ".
Other than the applied stickers, the boxes are the same and have the same lot number stamped on the inside of the end flap " 001-96 ".


Carton end flap.

Lot number on inside of end flap.

Brian


#2

A more literal translation would be “for measurement”, but that’s pretty close.


#3

Very nice photos!


#4

Reference cartridges are used for calibrating pressure test equipment. They are manufactured with extremly small tolerances and a propellant lot that is known for regular behaviour. With each lot there comes a sheet describing the rated pressure of the lot, obtained by firing it in a number of test barrels (round robin method).

Because experience shows that day-to-day variations of results occur, the lot you want to measure is fired in turn with cartridges from a reference lot.

For example, a reference lot might be rated at 2345 bar. Measuring it in your pressure barrel the result is 2445 bar. This gives a correction value of 100 bar (your test equipment is assumed to give results 100 bar above the real value).

Lets assume the lot you want to test gives 2500 bar in your test barrel. Then the correction value 100 bar (too high) is applied, and the tested lot is assumed to have a real pressure of 2400 bar.

This sounds like an extremely crude approach at first, but extensive statistical tests have shown it works (ballisticians say).


#5

Jonnyc,

Thanks very much for the translation.

Leon,

95% of it is the camera; I have a little Canon SX260HS digital that works wonders.

JP,

Thanks for information / lesson on the use of reference ammunition.

Brian