Video: How Much Does Barrel Length Affect 7.62x39 Velocity?

[firstchoice]

I ran across a video from Classic Firearms about velocity differences of rounds fired from various 7.62x39mm barrel lengths. Barrel lengths range from 8.3" to 21.5". Somewhat interesting, anyway.

https://www.classicfirearms.com/video/sep30-2022-how-much-does-barrel-length-affect-762-velocity/?___store=default&trk_msg=QNPLN25O9CF4334R3UINBVIFKK&trk_contact=525UJMSNEQ5S4IL6VU0CDN42FS&trk_sid=4BL6S26BV02D5IDVN0K4TTIQ70&trk_link=CV2GE3TTP5NKD6RQO31DSDHHLG&utm_source=listrak&utm_medium=email&utm_term=https%3a%2f%2fwww.classicfirearms.com%2fvideo%2fsep30-2022-how-much-does-barrel-length-affect-762-velocity%2f%3f___store%3ddefault&utm_campaign=20220930HowMuchDoesBarrelLengthAffect762Velocity&utm_content=Secondary

firstchoice

[Phosphorus32]

Interesting. Nice range of barrel lengths in Classic’s test.

The testers in the link in this thread removed variables with regard to type of firearm, barrel material, land and groove depth, but they only covered rifle length barrels.

https://sks-files.com/index.php?topic=4916.0

[Greatguns]

To me is seems basic, the difference is with the gas pressure by type of firearm. Gas impingement vs piston and then short piston vs long piston and also gas port size vs overall gas system length. All of those things are going to create variances in velocity on top of the barrel length itself.

[Greasemonkey]

I doubt gas systems effect the overall end velocity all that much, there's actually probably more difference in between barrels(no two barrels are perfectly identical), ammo deviation and inconsistency(there's always some deviation) to actually get a true hard number. Add in the moment of inertia is different for each weapon, or just when the gas system starts it's function, spring tensions and internal clearances.

[Dedeagach]

They needed more data