I just finished up my first lower build and I'm having three problems.

1.  When the selector is on "SAFE", I can not pull the bolt all the way back.  It seems that the hammer bottoms out and will not let the bolt come back.

2.  When the bolt is in the locked back position, it is imposslible to put the selector on "SAFE"....this seems like it would be related to the previous problem.

3.  The bolt catch spring has no spring tension, it just kind of hangs there and although it works, it isn't right...seems like the spring and bolt catch buffer don't move very freely, should I take a file to the bolt catch buffer or the reciever to loosen the fit up and let things slide?

The lower is a MEGA and the lower parts were gun show parts from what I thought was a reputable dealer.  Did I put something together wrong or are some of the parts out of spec?

Thanks for any help.

P.S.: Edited the title in case some needs to do a search.    

The back end of the hammer "hook" is hitting the rear part of the trigger.  If you have to, you can grind on that part of the hammer with no problems.



Yup - the same fix as No. 1.



Sounds like the bolt catch spring plunger is sticking in the receiver.  Loosen it up. I generally file on the cheapest part.  When you're done, try to polish the plunger and touch up the finish.



I don't think I've ever seen the words "gun show parts" and "reputable" ever used in the same sentance before.  [:D]  Looks like you got some funky parts that need a little "extra fitting."

**I don't think I've ever seen the words "gun show parts" and "reputable" ever used in the same sentance before.  Looks like you got some funky parts that need a little "extra fitting."**

    Good Call!  And thanks for responding Homo_Erectus
    Live and learn, actually the problem ended up being the trigger itself(material above the trigger that goes into the reciever actually).  I miced an old AR trigger I have that has been working fine and the new one, the new one was almost .08 larger in the than the working trigger (this is the part of the trigger that the disconnector goes into)!  This caused the hammer to jam this "extra material" into the lower reciever when the safety was on because the back end of the trigger had no place to go.  When safety was off, there was extra room for the back end of the trigger to move.  The terminology I'm using to describe the trigger parts probably isn't the best but in any case, it's fixed.  Just thought I'd share the fix in case anyone else would have a similar problem.

Thanks Again.

Actually, if you know what you're doing, and what to look for, gun shows are the ONLY place to buy parts. That way, you get to pick what you're buying and not depend on some high school kid working a part time job at a parts house to pick you out a decent set to throw in the envelope.

Understand this, ALL the aftermarket places are buying their parts from the same few makers.  Most of them are OK quality, but there is about zero inspection of what's coming in, before it's either put into a rifle or sent out on an order. The makers aren't inspecting them either.

Most of the innards in my built up ARs are GI surplus Colt pieces, and I got nearly all of them at gun shows; by asking the parts guy; "Where are your used parts". Then I look for the magic "C" stamped on the piece; or some other govt contractor mark.

Yeah, it takes some experience w/the field before gun show buying becomes the way to go, and a newbie is probably safest ordering from one of the bigger aftermarket houses, but know this; ordering from Rock River, or Bushmaster, or DPMS or one of the other big boys, will not guarentee you perfect stuff. I've gotten defective and/or out of spec parts from all the above, some in parts orders, and some installed in lower assys bought whole.