New to the Vepr world but I'm finally taking the plunge.  I'm leaning towards 54r simply because I have 1.5x lifetimes' supply of Bulgarian, Romanian and Russian surp ammo bought cheap and stacked deep.

1) I understand a 16" may be too short and will result in lower velocity, unburned powder and probably a fireball per shot.  People note that the Russians (developer of the 54r) never really issued any of their 54r weapons with less than at 20-21" barrel.  Even the PSL is around 24".  I'd prefer to go shorter if possible.  What if any performance difference would one find between a 20 and a 23" Vepr barrel.

2) I might keep the thumb hole stock but I've been thinking about dressing it in the beautiful Ironwood Designs SVD style stock set.   Any issues/concerns/opinions here?

3) Tabuk style flash-hider.  Any issues/concerns/opinions?  

4) Scope+mounting?  Opinions?

5) What's up wi Single-stack receiver?  Sheeze.

6)  What about a .308 version?  Is the receiver single stack as well?  Cost/availability of mags?  Performance vs. barrel length?

Yea I've since realised this.  Any other feedback?

I have a 23" Vepr 308 and a 7.62x39 on the way. My 308 is my favorite Kalashnikov ever and I have owned Arsenals, Saigas, Norincos, etc. My experience may go closely with the 54r, maybe..

1. I have a Mosin m44 carbine, it is a flame thrower with a 20" barrel i believe. I would personally go with the 23" and a good flash hider if flash is a concern

2. I went tactical on my 308 but those IWD stocks look awesome. If you add a flash hider, be prepared for the 922r game

3. I am using an Echo 93 AKML flash hider on mine. resembles the Tabuk but shorter (which is good for me with the 23" barrel) just an option but if i were doing the build you envision, I'd use a proper Tabuk copy

4. The receiver rail should take AK pattern mounts

5. This was one of the 2 reasons I went with the 308. The 308 is double stack and you can get Quality US made aftermarket mags from CSSPECS. the other reason I went with 308 is more available high quality/ match ammo as I do not reload.

6. As above, the 308 is double stack. I think the 308 is more efficient out of a short barrel than the 7.62x54r but I am not an expert on the ballistic differences. I have owned an LMT MWS and a Scar 17s and I never felt hindered with a 16" barrel. Mags are around $30-$40 from CSSPECS and they are excellent.  I went with a 23" barrel because that is what was available at an attractive price when I was shopping. I think for 308 18" is the sweet spot and if all lengths were available I would do 20" for 308 and 23" for 7.62x54r.

hope this info helps. Veprs are awesome