I take it the gen1 worked on AR15 but not the gen 2 if I’m reading correctly. 
The Gen 1 was more compatible, and it was the gen 1 that I was able to see at a gun show that sold me on them. However as a rifle I guess it was a bit of a jam-o-matic as it had no overinsertion tabs and was extremely fragile on the upper receiver. If you’re talking about the ones that used standard AR15 lower receivers and those dubious and proprietary civilian magazines those are called an AR-47.
After an experience with 450 Bushmaster as well as several pistol problems, I’ve decided that civilian magazines are horrible option and avoid them.
Maybe this will help you. Making An AR-15 in 7.62x39 Work Reliably - AllOutdoor.com
Yes… well I guess a few hundred bucks of machining on the feed ramp and upper receiver, hard to find 25 dollar magazines and discontinued parts from a company that went out of business is an option too but I personally opted for the Palmetto KS-47 that uses cheap military magazines instead. To each their own, but I don’t think a last round bolt hold open is worth all that, and that’s the only real difference I can see.
As stated, the lack of over-insertion tabs that gave the Gen1 compatibility with standard AR15 lowers and AR47 mags as an option is also the primary reason it had reliability issues, with mags dragging the bottom of the bolt. In the end, the draw of the KS47 for most folks was the ability to use AK mags so the moves made for the Gen2 were the right ones in my opinion. PSA was generous in working with me to update my Gen1’s that had issues to Gen2 uppers and bolts, without some of the other changes like the single large feedramp cut in the barrel extension. That was nice for me because I was able to keep the mid-length gas barrel that was available at the time for both of the Gen1’s I had, but otherwise get the key Gen2 updates.
I have 2 of the AR47’s that work with a regular lower. One of them was my first build, the other one I just put together a year and a half ago. They’re both ultra reliable. I shoot nothing but the cheapest ammo. The feed problem was solved long ago. I’ve had great luck with ASC, Pro, and C Products mags. They work, they’re great.