I was wondering if you all can give me a little feedback. I recently built my second AR. I purchased a Stag model 3 the first time and felt that I wanted to build the second. After a lengthy delay, I got it on Feb 26th. Spikes tactical lower (zombie edition) Amazon.com buffer and spring ( idk the brand, found it online and tried it in the stag and it worked well so I stuck with it) DPMS lower parts kit (I know, its cheap) rguns 5.56 1/8 twister barrel upper with a carbine moe handgrip. Bolt and carrier was included. So I took the new gun out the day after I got it. I shot 20 rounds out of it and had it fail twice. The casing gets caught between the bolt and the chamber. Took it out again yesterday and the same thing happened but this time it was 4 out of 20 rounds. I am attributing this to a Tapco gen II mag. I used the same mag both times and the problem only happened with that one. Knowing that ammo is expensive right now, I even used a USGI for about 10 more shots and didn't have a problem at that time. I put the Tapco in my stag and experienced a different problem. The round would get caught on the front of the magazine and not allow the bolt to push it out of the magazine. I again (never ever having a failure for the 1000 + rounds or so that I have shot out of the stag) switched to the USGI and didn't have a problem. Bringing the Tapco mag home and taking it apart, I noticed that the feeding lips are tapered but it seems normal for the tapco after comparison with pictures of other tapcos. I am just wondering if anyone has any other pointers. I think I am on the right track but I am a new builder of AR's and admit that I have used some cheap parts in certain areas.