I'm thinking of ordering this barrel for an M70AB2 underfolder parts kit, but I'm not sure if it'll fit.  Green Mountain says it fits "most" M70's.  But I don't know, do all M70's use the same barrel?  Do milled and stamped versions use different ones?

From GM's site:

AK47 Replacement Barrel Compatibility Reference Table.

AK47-1GM: Yugoslav M-70 Pattern Barrel suitable for most Yugo M-70 series rifles.
AK47-3GM: AKM pattern barrel. Will fit most Russian, Polish, Romanian, East German, Egyptian, and Hungarian pattern AKM kits.
AK47-6GM: Yugoslav M-76 sniper rifle barrel.
Ak47-7GM: Ak47 Type 3 Milled receiver barrel. Will fit most Russian, Polish, Bulgarian, and Hungarian type 3 milled receiver kits.
AK47-RPK-GM: RPK barrel for Russian and Romanian rifle kits.
AK47-10GM: Will Fit Most Russian 5.45mm kits.

I would measure the insidebof the trunnion, email curtis at ak builder and see if he has a yugo barrel that will fit nicely, barrel outer diameters and trunnion ID’s vary wildly in ak’s, yugos use the larger milled receiver diameter in their stamped guns, best to measure first then buy

AK Builder does have an M70 barrel that you can get in two different trunnion sizes, but it's not chrome lined like the GM.  I would prefer chrome lined if it'll work, but it's an option.

Apart from determining the correct trunnion size, is there anything else that would differ between barrels for the various M70 models?  It would suck to buy a barrel and find out the gas block doesn't fit, or something like that.

ETA:  I fail at reading, the AK Builder barrel is chrome lined.

Do they have the nitrided barrels, those are really nice, i built an underfolder with one and it was excellent. Usually, the gas black fsb and rsb are good, i would measure anyway to make sure that they wasn’t more than a couple thousandths of interference, if it looked like it was going to be to tight i used a brake cylinder hone to open them up a little, unless the barrel is wobbling around in it once you pin stuff it its not moving. You gotta remember, Yugoslavia had no known chrome deposits so their military rifle barrels were not chrome lined, but their ammo used actual copper jackets not copper washed steel, i would go with a nitrided barrel, for thebpricebit cant be beat

They do have nitrided barrels, but I'm concerned about having trouble drilling them for the gas port, barrel pins, etc.  I do like nitrided barrels generally, but I've never had to drill one before.  I've heard it can be tough.

They do offer chrome lined M70 barrels:

https://ak-builder.com/index.php?dispatch=products.view&product_id=30594

Good sharp shallow angle drill bit should go right through it, the hardened layer isnt very deep, but all the guns i built where i populated the barrel were not nitrided, nothing wrong with chrome lined at all, millions are out there in crappy countries working fine after being abused

Yep, I'm going to order a chrome lined one from AK Builder as soon as I get the stub out of the trunnion so I can figure out what size I need.

I would prefer a bit higher quality barrel, so I ordered a GM1 CL barrel for a Yugo M70AB2 kit that I got last week. Yes it was more expensive, but what the heck. While there were two NOS Yugo barrels in my stash, I took one of them & compared the barrel journals dimensions given on the GM spec sheets & they were either spot on or a few thousandths larger. The barrel trunnion was spot on, so the journal sizes should not be an issue. The barrel that came with the kit was a really nice barrel, unlike the sewer bores that came in years ago, too bad they had to chop it up like they did.

Fake news. Quite the opposite, actually.

Why people still believe this when they produced the M85 and M90 with chrome lining for years is beyond me.  They didn't chrome line the M70 because the military didn't want them chrome lined. That's it.

I ordered a M70 B1 kit from PSA and received it this past Friday. It was all there except the barrel & receiver & all parts were matching & in good shape for building. It is a 1995 year of manufacture . The wood stock had some black greasy stuff on it that totally covered the wood, but it looks like it will clean off with a bit of elbow grease. Green Mountain & Childers will get a bit more business from me next month when I order another barrel & receiver. Neither kits had the Zastava stamp on the rear sight base for some reason, unlike the other kits I got years ago. These two builds will have perfect barrels rather than the war worn ones that I built years ago.

As of now, there are 4 Yugo M70 series rifle kits in my collection from PSA & they are all in very good condition with all matching numbers. The first one is built & completed with the second one still in the demill & trunion hole fitting for the 80% receiver. Receivers are 3 months out from purchase & GM barrels are out of stock @ the moment. I have enough to keep me building till the next receiver shows up in a few months.

The Green Mountain barrels did drop in price by $30.00 since I started buying them for some reason, but no complaints from me. They fit the built & shoot very well.