I cross posted this in the AR ammunition forum before I realized maybe AK guys would have more info on the caliber. I'm trying to figure out in a 7 to 8 inch barrel what the velocity and energy would be so I can compare it to 5.56. Looking at it's performance for hunting.
Thanks.

Micro Draco 6.25"  
~ 1800fps

Mini Draco 7.5"    
~ 2000fps

M92 PAP 10.5  
~ 2100fps

Draco 11.5"  
~ 2200fps

Krebs 103K 14.5"  
~ 2350fps

AK 16.5"    
~ 2350fps

SKS 20"  
~ 2400fps

RPK 23"    
~ 2440fps

These are all approximate and will vary depending both on the gun and ammunition used but should give you a decent idea.

124gr pill at 2000fps out of a 7.5" barrel is pretty darn impressive.  

X39 is a sweet round...  

I have about a couple cases of 8m3, it's good stuff.  23cpr legit defensive/hunting ammo.  Expansion is good and it's barrier blind...  gotta know which brand is selling it at a particular time, it shifts every couple years, I believe.  More accurate than FMJ too.

All my ak's are 16" though

2000 fps is good. A 5.56 is only going 2000 fps out of a 7.5 and it's only 55 grn. Theoretically I guess 7.62 must have about 2.5 times the energy? The bullet weighs 2.5 times as much.

It's been a while since I took a physics class, but I want to say that kinetic energy is velocity cubed times mass.

A 124gr 7.62x19 pill going 2000 fps out of a 7.5" barrel is... optimistic. 1600-1800 is a more realistic range. The 7.5" barrel is about as short as you can go in this caliber while still being able to get bullets to be useful on a target with some regularity, and then only barely. Bulgy 8.5's are the shortest that will still have mostly reliable terminal performance. Most rounds, even high end ones, in this caliber will want to be going at least 1900, with a couple exceptions from makers of subsonic rounds (Lehigh Defense and EBR).

https://youtu.be/lbgAh9-sCDQ?t=1m14s