Just a word of caution for you guys. Part of this post is a reply to a thread Gun Runner started, but there were so many issues with this upper I wanted to make a separate post. A buddy came over yesterday with his new AR 5.56 pistol build that he was having problems with. He bought the upper from 22mods4all for $209, a very cheap upper. The BCG was a fail zero bcg that was on sale for $100 a couple weeks ago. The problem he had was sometimes when the bcg did close all the way it was really hard to get it to return back with charging handle (when closed by hand) and when shooting, it sometimes didn't chamber a round, it failed to go fully fwd. We stripped it down to remove the gas tube. The gas tube mushroom end mic'd at .080 or so and had a burr on it. It also would bind when going into the gas key on the bcg, we tried 2 bcg's as well, both were the same. Turning it by hand in 220 grit sandpaper cleaned it up and it now reads .0785. It then moved freely in and out of the gas key, when reassembled the bcg moved slick as snot with no binding.
The setscrews in his low profile gas block were also metric which was a surprise. Glad I have a full set of metric allen wrenches. The barrel wasn't dimpled for the set screws either, so we dimpled the barrel so the setscrews could get more bite on the barrel. Eventually they would have come loose and the gas block would have shifted, you can be sure of that.
The screws attaching the forward rail to the barrel nut were rather odd. They were 10-32 pitch, but neither a metric or standard allen wrench would fit in the screw head properly. While we got them out I was concerned about putting them back in so I gave him replacement screws what were made to a much higher standard.
Anyhow, the moral of the story is, if you buy a cheap upper, expect to have problems, consider it as buying a kit you are going to have to fine tune.
I forgot to mention, the low profile gas block and gas tube had the wrong size roll pin installed. It was tight to the tube, but loose in the block. Luckily I had some spare pins on hand.
The setscrews in his low profile gas block were also metric which was a surprise. Glad I have a full set of metric allen wrenches. The barrel wasn't dimpled for the set screws either, so we dimpled the barrel so the setscrews could get more bite on the barrel. Eventually they would have come loose and the gas block would have shifted, you can be sure of that.
The screws attaching the forward rail to the barrel nut were rather odd. They were 10-32 pitch, but neither a metric or standard allen wrench would fit in the screw head properly. While we got them out I was concerned about putting them back in so I gave him replacement screws what were made to a much higher standard.
Anyhow, the moral of the story is, if you buy a cheap upper, expect to have problems, consider it as buying a kit you are going to have to fine tune.
I forgot to mention, the low profile gas block and gas tube had the wrong size roll pin installed. It was tight to the tube, but loose in the block. Luckily I had some spare pins on hand.
