Here is what is going on: I got one of those 10.5 uppers from PSA and then tried to put it on a new lower with the SBA3 brace. I went to do a function check.
With the mag well empty, I tried to manipulate the bolt catch to hold the bolt open. It failed. So, I changed the bolt catch out with a new one. It failed. I tried a shorter buffer tube. The bolt catch still would not work manually (though it would stay open on an empty magazine.) I swapped out the bolts and mag catch still wouldn't work manually.
Over the weekend, I went to a gun show, found a guy with a complete pistol lower and put the PSA upper on it. I cocked it and tried to get the bolt hold to work manually. No luck. So, the problem is in the upper receiver, but what could be wrong with it?
With the mag well empty, I tried to manipulate the bolt catch to hold the bolt open. It failed. So, I changed the bolt catch out with a new one. It failed. I tried a shorter buffer tube. The bolt catch still would not work manually (though it would stay open on an empty magazine.) I swapped out the bolts and mag catch still wouldn't work manually.
Over the weekend, I went to a gun show, found a guy with a complete pistol lower and put the PSA upper on it. I cocked it and tried to get the bolt hold to work manually. No luck. So, the problem is in the upper receiver, but what could be wrong with it?