I have used a 105 and two of the 103 models in 7.62x39. Overall they work well, they do have some issues and roughness, and none that I used were perfect out of the box, but nothing really that bad. The one common bad thing is that the wood stocks are kind of iffy and would really benefit from a bedding job.
Of the 3:
-one had some roughness on the bottom side of the bolt where it would slide on the receiver when cycling the action, so it didn't slide as smoothly as some guns, but functionally it worked fine.
-one had a little too much wood taken off where the trigger guard is sunk into the wood, so the bottom edge of the trigger would rub and sometimes catch on the inside of the metal guard. I could have filed a bit off the bottom of the trigger itself, or tried to bend the guard out slightly, but I found a few small washers to shim it out made it sit flush with the wood around it and fixed the problem fine.
-the last one was probably the worst, where the extractor is ramped to slide over the rim of the cartridge when pushing forward was a little less ramped than it should have been, so it could be a little fussy when pushing the bolt forward. It's annoying, but nothing you can't deal with once you know how to make it work. You could probably carefully file the ramped part, or maybe lighten the spring a little, but I'm not confident enough to start doing that myself. This one also had the scope mount slightly misaligned. They were close enough that some scopes would work, it depended on how much adjustment they had, but others would run out before you got it sighted in. I found the easy fix was a set of burris rings with the plastic inserts worked for the scope I had that wouldn't adjust far enough.
Now for the good things!
I'm not a bench rest shooter, and I can't get MOA with any gun regardless of how accurate it is, but when I really sat down with it, I was getting better groups with the 7.62x39 jw-103 than I was with my savage 16 in .308 at 100 yards (this was with brass cased non corrosive norinco from canam vs white box Winchester). This may be from less recoil translating into less unintentional flinching/compensating, or it could just be that the gun shot well.
The triggers were actually pretty decent. Not amazing by any means, but not nearly as bad as I was anticipating. Not sure how adjustable they are, I never really looked into it as I was happy with how they came.
The mags are single stack box mags, so they stick out of the bottom of the gun, so you can't carry it one handed by the magwell, but they're pretty robust feeling. The mag catch reminds me of older savage 340's or bolt action shotguns, but it worked.
They're pretty light to carry and balanced well carrying it. This is where the not quite hardwood stock made it fairly light (I didn't measure, just overall impression).
The bolt is fairly simple design, not many moving parts, doesn't seem to be a whole lot to go wrong with it. I don't know what replacement parts are like, but I've had people mention it looks like a BRNO clone, but I don't know them well enough to comment.
All in all I would say I am happy with what I got out of them. They're a cheap fun way to get in some trigger time and practise and really I like the feel of it better than an axis, and you could use it as a learning experience in bedding or polishing without feeling bad if it didn't turn out 100%.
