Is the veper bore .308 or .311 or something else?

I want to load for it and have lots of .308 bullets including tracers.

Anyone know the twist rate for the 20.5" barrel?

What bullets/ loads work best for you? Give me a starting Point

We need to know what caliber yours is, then we can tell you the details. They come in a whole bunch of different calibers.

If it's 30-06 or .308 it'll have a .308 bore.

If it's 7.62x54R it'll have a .311 bore.

I have 7.62x54r

Wouldn't it be odd for them to have two different sizes 30 caliber barrels?  Just as an supply standpoint two different sizes could be nightmare.

There wouldn't be anything odd about two sizes of 30 caliber barrels. American 30 cal. is .308 dia. while the Russian is .311. I'm sure they have a system that keeps them from getting mixed up and I'm sure they are clearly marked.

I couldn't find anything specific to the VEPR's twist rate but the cartridge uses a 1 in 9 1/2'' twist. It would be easy to find out for sure (I don't have mine yet). Put a cleaning rod with a tight fitting patch down the bore like you're cleaning it, push it into the receiver then start pulling it back out. When it's into the rifling make a mark on the rod at the top at the muzzle. Slowly pull the rod out watching that mark, when it makes one turn make another mark on the rod. Pull it out and measure the distance between those marks and you'll have your twist rate.

1 in 9 1/2'' seems a little fast for 30 cal. but the 30-06 uses a 1 in 10'' so I guess it makes sense.

As far as what bullet is most accurate, I couldn't tell you for sure, again, I don't have mine yet, but you have a lot of bullet choices. Anything from 140gr to 200+gr. Most commercial ammo is a 150gr bullet but it seems Mosin's favor something around 170gr, at least my most accurate one does. I have a real good load made with a 174gr Sierra Matchking, maybe that would be a good place to start.

When mine comes in I'm going to try that load, see how it does then make adjustments if needed.
Good luck.

ETA: About 2 hrs ago I got a call from my LGS saying my rifle is there ! I hauled ass down there and picked it up. Wow, beautiful rifle, well built and nicely finished. I like it !
I checked the twist rate and it's 1 in 10 3/4''.

Veprs are known for beating the hell out of brass. I don't reload now but have saved some of the brass I've shot from my 54r Vepr and you don't get to save much. There's a thread over on vepr.org that shows the kind of damage to expect.

Thanks for the heads up.
I just chambered and extracted a round (brass cased) and it was scratched on the body and the rim was nicked up. Just from doing that one time. I can imagine the damage it'll cause when fired.

I'll take a look at that site and see what's going on.
Thanks.