I have had this rifle for a long time. The bolt catch area of the receiver has too much space where it was constructed. USGI 30 rnd magazines work o.k., but PMags and USGI 20 rnd magazines fail to hit the catch. The rifle functions well, but this magazine issue is the only thing bugging me. The receiver was made by PWA and I couldn't just dump it for another anyways (reg assault weapon here in CA). I already tried to shim the gap for the bolt catch, but the "finger" was still too short to be pressed by some magazine.
I found a way to correct the problem using a Colt 9mm bolt catch and it now works well
Here is a photo showing the bolt catch failing on a few magazines:
First is a PMag, second is a USGI 20 rnd, third is a USGI 30 rnd with Magpul follower (works)
After stripping out the old bolt catch, along with numerous measurements, I test fit the 9mm catch. It was very long, and that is just what I needed.
I fit several magazines and determined the overall length of the bolt catch needed to be in the area of .470 inches. That would allow enough room for different magazines and ammo, leaving enough room between the bolt catch and the back end of ammunition being fed from the magazine. I didn't want the bolt catch to drag across ammunition primers or rub the back of ammo while it was being fed from the magazine.
After fitting, a gap of a bit over .270 inches between the bolt catch and the base of ammunition.
This phot depicts the bolt catch final stages of fitting. I had to polish the bolt catch a bit in some areas. I found the top edge of the bolt catch was rubbing one of the bolt lugs.....The bolt catch was polished and slightly rounded where it was rubbing the bolt lug....This area was only rubbing when the magazine follower pushed the bolt catch upwards while the last round was being ejected from the rifle. After polishing, the bolt lug glides over the bolt catch without effort.
All that is left is to function test with live ammo, then cold blue the bolt catch. Overall, this was fairly easy to fix. I just had to take my time and test fit the new bolt catch a bunch of times. This rifle will now lock open on ALL my magazines, 30 rnd USGI, 20 rnd USGI, PMags, etc. Very happy now.
It is possible that some out of spec receivers that have problems with PMags not locking open can be fitted with a 9mm bolt catch like mine.