Built my 9mm AR using a 22 mods for all upper 5 1/2 barrel and bolt assembly on an Anderson lower. Pistol build. Ran original on an FMG polymer lower about 250 rounds and it cracked. Rebuilt on Anderson lower and finally got a chance to take it to the range a couple of days ago. Nothing but problems. Single shot then jam. Round in chamber and feed round jammed. I should mention took out original buffer and replaced with a 5.5 oz buffer. Also shimmed the buffer spring with 4 quarters.Bolt still retracts more than needed but wanted to start small. OK after a few jams suddenly it decided to run the whole 32 round mag with no further issues. Loaded second mag and again jam-o-matic. Opened upper when a empty jammed and found the bolt hold open casting broken (like the first one), same place same item broken. Did notice that when I inserted the mag on an open bolt it didn't always catch on the mag lock and it did insert somewhat too far. Thinking that that might have been the cause of the broken bolt hold open device. I like the bolt hold open but am beginning to think it may not be all that important if that is the only issue. (P.S. Using Colt style ProMags which ran well the first assembly).

Any thoughts and or assistance appreciated again
Did sent adapter back to ProMag for second replacement for the same issue.

Hey if you dont mind, I think ive got some stuff thatll get you running if you have a pmag.

Ive been designing some parts just for PCC ARs to overcome some of these issues. If its built on a standard lower thatll take a standard mag.

All I ask is that you gimme feed back on the parts and let me know how they worked.

Heck I'd be interested in that, compare it with my Endomags.

For the OP - instead of getting another block, consider either shooters offer or using Endomags.

Deal. Pm me your address, and do you shoot pmags or standard metal gi mags?

Im working with small part quantities right now and until im 100% sure theses are good to go i dont wanna dump several thousand dollars on mold contracts and things. Just been testing them local so far, but I think im ready to move forward a little.

Mean arms makes 9mm adapters that fit in gen 2 and up pmags, and they work great.
endomag
I bought 9 of them when they were pre ordering, and I have been happy with them. I learned long ago to never buy anything from promag, especially magazines.

Sent E-Mail per offer, yes I'm interested. Forgot to state in e-mail I use whatever mags I can get. Have mags from Shooters World and a few metal GI style mags currently. Just let me know what mags I need and I will get same.

Otherwise I know the reputation for Pro Mags but this weapon ran perfectly in it's prior configuration with the Pro Mags until the lower cracked  and I stopped shooting it. It is still the same weapon only difference's are Anderson lower (same Lower parts kit reinstalled) and a heavier buffer. Went from a 3.5oz to a 5.5 oz buffer. As i stated my only thought after getting home was maybe the magazines were inserting too deep as the mag catch is very tight and doesn't always catch the mag and therefore the breakage of the hold open arm on the adapter from mag insertion going too deep but at this point even that is just a guess. The first round chambers fine but it jams when trying to feed the second round, remove mag, reinsert and same issue but after 4 or 5 jams suddenly runs OK and empties mag with no further problem. Insert second mag and it starts all over again. Finally got a jam so bad I needed a screwdriver to remove empty case and did not have one with me so just quit and went home discouraged. Found broken hold open arm just prior to leaving range, got home, called Pro Mag and sent adapter back for replacement.

Got your email, and ill send you a couple things in the mail this coming week.

Thanks. Will let you know when they arrive and after how they work.

Tks....Don