My goodness, what an amazingly erroneous statement. The 7.62x39 in no way is interchangeable with the 7.62x54, nor the 5.56x39 with the 5.7(about)x44. The only interchangeability I have found is that the 7.62X51(NATO) round will chamber and fire from the 7.62X54(Russian) Mosin-Nagant. Once.
Extraction is another problem - the Mosin-Nagant requires the uniquely thick rim of the 7.62X54 for the extractor to grab and pull the shell fron the barrel. Also, there appears to be some slight brass swelling on firing.
In fact, the unnamed person I know who tried this ended up having to drive the brass from the chamber from the muzzle end with a ramrod. But this was primarily because the idiot at Sears who sold the rifle ($15.00 for the "sporterized" version circa 1966) included a box of NATO surplus ammo with it. Hell, Dad didn't know the difference (woops!). The gun was never fired again until I figgered out what it was about 1974 and bought the appropriate ammo for it.
That's when I found out Mosin-Nagant was Russian for "big muzzle flash".
That's when I found out Mosin-Nagant was Russian for "big muzzle flash". Especially if you use the heavy bullet loads meant for use in the DP *Emma*, PK, and Russian Maxim machineguns. Meant to rach out and scratch away at formations of troops as much as 2000 meters away, they offer a bad enough kick in a 30-inch barrelled *3-line* MosinNagant. Just as bad a mismatch: Norma 7,62x54r marked soft point hunting bullets actually loaded with .308 bullets that offer fairly minimal accuracy results in the rifles' .311 bores. The suoerb Finnish M28-30 rifles used .3082 bore diameters, and deliver excellent results with this ammo, just as they did in every international riflery competition they entered from 1927 on, though they won't shoot for beans in the average Russian bore. Find a guy with an m/28-30 pytstykorvaa and offer 'em as trade goods to ther specialists who can make use of 'em.
