crossrhodes
Member
Hey Gents, Here's one for a guru to figure out. I had a customer order an AR upper, standard M4 with 14.5 barrel. The upper came in and the customer showed up with his classIII lower, he has a tax stamp and everything is legal. I installed the upper and we stepped out side to test fire. Well, it operated fine on semi but when he went to full auto it would only fire one round. It appeared that the auto sear would not engage the hammer and the hammer would follow the bolt and the round would have a light dimple. As I stated, it worked fine in semi.
We tried 3 other uppers of various manufacturers on the same lower and they all worked fine. We even used the same bolt in all three uppers.
We called the builder of the upper and explained the situation, he said to send it back and he'll take a look at it. Two weeks later I get it back and it did the same thing, we did the same thing with three different uppers and the same lower and had the same results...All three uppers worked and the return upper didn't.
In short, The builder told us to pound sand and the upper was fine and we were idiots...not kidding, his words. I won't mention his name.
I was thinking that maybe the bolt carrier tunnel was a little over sized and the bolt was tilting up on recoil and not pushing the hammer down far enough to engage the auto sear? Reason is because of the unusual wear marks inside top of the receiver. So what do you think:banghead:
We tried 3 other uppers of various manufacturers on the same lower and they all worked fine. We even used the same bolt in all three uppers.
We called the builder of the upper and explained the situation, he said to send it back and he'll take a look at it. Two weeks later I get it back and it did the same thing, we did the same thing with three different uppers and the same lower and had the same results...All three uppers worked and the return upper didn't.
In short, The builder told us to pound sand and the upper was fine and we were idiots...not kidding, his words. I won't mention his name.
I was thinking that maybe the bolt carrier tunnel was a little over sized and the bolt was tilting up on recoil and not pushing the hammer down far enough to engage the auto sear? Reason is because of the unusual wear marks inside top of the receiver. So what do you think:banghead: