8" krinkov has 2400 fps at the muzzle
12.5" ak-105 has 2800 fps at the muzzle
16" ak-74m has 2900 fps at the muzzle

What barrel length would you prefer in 5.45x39?  Has anyone done any tests of 5.45x39 out of SBRs at range and terminal performance / accuracy?

I'm curious if a 8" 5.45x39mm projectile variants would still tumble and have sufficient energy at 200m.  Wikipedia says it will be traveling about 1850 fps and have 400 ft lbs of energy at that range, or slightly more than getting hit with a standard 16" ak-74 at 400m.

Would love to hear thoughts and have a good discussion on 5.45x39 out of SBRs and its effectiveness.

could mods move this to ak pistol / appropriate sub forum?  sorry and thanks!

I'm pretty sure you explained yourself the reason why the Russians have largely switched to the 12.5" AK-105 layout for that application. That's a huge FPS loss for a marginal difference in overall length.

Topic Moved

Sure its a big FPS loss but do we know the extent of the terminal performance loss of. 400 fps in 5.45?  The round tumbles and is less reliant on velocity than 5.56.  From what I gather the 5.45 tumbles at ranges where standard military issue ball does not.

what ranges? I've shot my 5.45 out past 500 and didn't witness keyholes...

Not keyholing, but does 5.45 tumble once entering a fleshy target at say 300-500 out of an 8" barrel?

well that's not what you said, so I apologize for the confusion.