the hex Mosins tend to have much worse barrels than the round receiver ones
That's way too broad a generalization. Hex vs. round is not that big of a deal. It tells you something about when and where the receiver was made--that's it! There are hex receiver 91/30's with minty bores and round receiver 91/30's with Stalingrad bores. And a great many of both that were refurbed and rearsenaled after the war. When you move beyond Soviet rifles the receiver tells you even less.
You need to do a hands-on inspection to be able to draw any conclusions about any mosins. And really you need to shoot the thing with a variety of ammo. Here are some pointers:
--First pull the bolt out and of course verify it is totally unloaded with no 54R nearby. This permits you to freely inspect the action. Inspect the bolt face for pitting which may show poor cleaning by the prior owner.
--Eyeball the bore by pointing the barrel at a bright light and looking through the receiver. Flip and repeat, being careful not to sweep anyone but yourself (the bolt is OUT now remember). You need to look to see if the crown is intact and if there has been a counterbore. You will often see some wear and tear towards the crown. This is usually fine, so long as you have even wear on the crown itself. But ideally you'll see sharp lands out to the crown. The crown can be rebated, as with M39's, but this is different from a counterbore that puts the crown back in the barrel and effectively shortens the barrel.
--Feel the barrel/stock fit and inspect the wrist for any cracks or incipient cracks.
--Inspect the shank and receiver markings. They will typically tell you who made the barrel, when the barrel was made, what nation(s) it came from and whether it was refurbed by the soviets.
--Observe the machining marks. Wartime USSR receivers are often very roughly cut and have an unfinished look to them.
--Observe the stock design and condition. It should have shellac if soviet, and if Finn it should have a dark stain. Almost black sometimes. Is it two piece? Has it been cut by Mr. Bubba?
--Check the interreuptor/ejector for springiness. It should be pretty stiff and have a non-eroded interruptor tip. Easy to replace, though, so it's not a deal breaker.
--Reinsert the bolt and check the trigger pull. Cycle and dry fire a few times, with the owner's permission of course, and of course pointing at something that can safely stop a 54R. The planet ideally. The bolt should not be tight, but rather should feel limber and kind of loose in the hand. It should have no points of unusual stiffness.
