I just got the Beryl AK rifle   in 5.56 and  both the ac unity ak19 and standard 5.56 mags to try out. I was surprised how well the RB Radom mag that came with the rifle fit. I've never had an AK mag fit so well it was perfect and clicked right in with no slop or wiggle. Now the ACU mags were a different story i had to shave down the plastic above and below the rear lug . Above the rear lug allowed the mag to clear the safety stop plate. (one could just keep inserting the mag a hundred times to shave off the plastic ) . Below the lug allowed the mag catch lip to seat all the way against the magazine body. I also filed down the bottom side of the rear lug like so many people have suggested and this allowed the mag catch latch to completely seat. Fitment was solid and i was able to get a similar click in fit like the FB mag.
NOTE-  You can file and file on the bottom of the rear lug and not notice the plastic above the rear lug is snagging on the safety stop plate.

Extra small parts below that came with the rifle. I had the additional left side selector and pin on brake added.




The way i fit the ACU 5.56 mag to my Beryl. Pictured below is my Work Sharp knife sharpener that helped sand the area's pictured.

1. I lightly sanded this are to allow the mag to clear the center support rivet/post. Dont go too much or you get back to front looseness.
2. I filed/sanded the bottom of the lug to allow the mag catch to close fully.
3. I filed/relieved  this area to allow the mag catch to clear the plastic and fully close. NOTE : I also relieved the area above the lug to clear the safety stop plate.

For the ACU mags I just jam them in and force the mag catch closed a few times. It shaves a little bit off of the rear tab - it's just made of zinc alloy so the mag catch will take care of it. After a few goes each mag is g2g.

Interesting that it came with spares. The stamped steel plate is the reinforcement bracket for the OG Beryl side folding tubular stock. They are (or were once upon a time) hard to find and almost never came with the Beryl stock when you bought a surplus one. Without it the stock will tend to want to flex up/down during use.

Isn't that bracket also used on the adj stock ? I see the same slots in front as the side folder.

Probably. I don't have one of the newer stocks so I can't comment.

Hey, nice job getting the ACU mags to fit properly! I've heard that can be a bit of a challenge. I'm curious, did you notice any difference in how the RB Radom mag performed compared to the ACU mags? And yeah, that reinforcement bracket is a nice touch - it's always good to have spares, especially for parts that can be hard to find. I've heard that bracket can make a big difference in the stability of the stock, especially during heavy use.

After fitting a couple of ACU mags i found a pattern that's repeatable and fairly quick . I haven't shot them yet but after much research it seems they are reliable in feeding but may or may not hold the bolt back which doesn't matter to me as i prefer not to have that feature. The FB mags are military tested and in use so i have no doubt in their reliability. Of course they are just plastic and can be broken when you throw your gun on the ground like the yahoos on YouTube.