450Bushmaster.net

Hello all. Long time lurker; first time poster.

I put together a new AR-15 in 450 Bushmaster this month to take advantage of the recent changes to the Ohio hunting laws. I got a GLFA upper from Midwest Firearms, a PSA lower half with the EPT trigger and ACS-L stock, and AR-Stoner mags from Midway. Topped the thing off with a Bushnell TRS-25 red dot with a dab of lok-tite. Bore sighted it at home and took it to a range last night to zero it in. What a disaster!

I managed to fire 8 rounds in 30 minutes. 2 light strikes that dimpled the Hornady ammo, but did not ignite. 1 FTF that required 2 hits on the forward assist to chamber. 1 FTF where it just didn't pick up the round from the mag. Twice the extractor didn't grab the shell. 4 shots required me to turn the gun to "safe" in order for the hammer to cock (always on a follow up shot). Not a single hole in the paper (18"x18") at 25 yards using a lead sled.

I haven't done any customization other than to add a QD end plate for a sling, so the only work I've done myself is inserting the pins to attach the two halves. I thought I was having problems with just the upper until I started to see the hammer cocking issue. I admit I'm not using top shelf components, but I do expect the thing to go bag when I pull the trigger!

I have another (inexpensive) AR that I put together out of a compete upper and complete lower that has the light strike problem on the first shot after sitting in storage, but none of the other issues. I have no idea what's going wrong. Any help is appreciated.

Sorry to hear about the problems. First off, for the shots that did go off where was your brass landing? On a new gun it should have been run really wet. If not it is hard to get the bolt carrier smoothed out. Sounds like maybe gas block may be slightly off. Not enough oomph to run things. First try switching to a proven lower. Try and see if same issues

kind of like buckeye suggested, you should also try the lower with a different upper to see if it exhibits the same symptoms.

thats always a good place to test.

I don't recall ever hearing about similar problems with the 450b like the ones you describe...very strange stuff. Keep us informed.

I had really weird/bad FTF issues with my factory Bushmaster mag. My Bartz mag worked perfectly though.
I didn't have any light strikes or trigger/hammer issues either. If you have another AR, swap the lowers and give it a go. Shoot both guns so you can see whether the problem follows the lower, or stays with the upper.

I also built mine myself.
Anderson Lower + PSA LPK
Bushmaster Upper

Thanks all. Finally got it worked out and forgot to post!

The buffer retainer pin apparently broke, came out of place, and went into the lower. The buffer retainer spring was wrapped up and over the hammer. Have since replaced with a titanium one and no more problems.

i love a story with a happy ending!