AR trouble.

[TTuck1911]

I have shot around 5,000+ rounds out of my Bushmaster since I bought it and am just now running into problems. Recently on a prairie dog hunt in Wyoming I shot somewhere close to 500 rounds out of it. Near the end of the 500 mark, it started having problems with cycling. The rifle would eject a round, but wouldn't cycle another one forward. After cleaning it, It was hard to fully close the receivers and put the rear pin back in. I shot it afterwards to make sure it was o.k. and it shot the first magazine without problems. After putting another magazine in, it resumed the non-cycling problems. I'm no expert on AR-style guns, but I don't consider myself to be ignorant on them either. I think the problem is going to be in the bolt, or gas system but I don't know. Any enlightenment on the subject would be greatly appreciated.

 

[Storm52]

Buffer & spring condition?

 

[SpeedRacer]

At that round count I'd replace the buffer spring and bolt carrier group. At least check the gas key on the bolt for damage and make sure the screws haven't backed out, since Bushmaster doesn't stake them. You can test the rings on the bolt by extending it forward in the carrier and placing it boltface down on a flat surface. The bolt should remain extended and support the weight of the carrier.

A new gas tube probably wouldn't hurt either.

 

[TTuck1911]

Buffer and spring are in excellent condition, bolt sucks and the gas tube is a few hundred rounds old. thanks for the help though.

 

[Akajun]

First things first, get a chamber brush and clean the chamber, very well. Maybe even plug up the chamber and pour powder solvent into the chamber and let it sit overnight, the scrub again.

Next disassemble the bolt from the carrier and make sure you dont have a buildup of carbon in the back of the hole for the bolt. Also make sure that the gas key is not built up with carbon. A drill bit will clean it out.

Next I would check the gas tube as it sticks out from the inside of the upper reciever. These wear and get shorter. compare it to another gas tube on an known functioning rifle, with calipers even, if you have some.

Also, disasseble the trigger assembly and make sure there is not an accumulation of trash or a blown primer under the trigger or hammer.

 

[TTuck1911]

Thanks for everyone's input on the question, but it turned out just to be an aftermarket gas block that didn't line up properly. It is still functioning perfectly without any replacement of parts, the original gas block has been re-installed.

 

[Vanilla Gorilla]

better take the time to stake the gas key anyway. A Cold Chisel or Punch is all you need.

 

[SpeedRacer]

Thanks for everyone's input on the question, but it turned out just to be an aftermarket gas block that didn't line up properly. It is still functioning perfectly without any replacement of parts, the original gas block has been re-installed.

Well leaving out details like that doesn't exactly help us diagnose it.

Aftermarket gas blocks (especially improperly installed) are one of the most common causes of gas related issues I've seen. I've personally sworn off clamp-on style gas blocks entirely.

 

[BayouSlide]

For the record, Bushmasters do have staked gas keys...just not very studly staking in some cases.

 

[tactical723]

Curtis, you ready to get rid of the Bushmaster yet for pennies on the dollar, my wallet is full? you know the pretty OD one from KY, lol..... See ya at the Corinth match !!

 

[BayouSlide]

Cashed in my original Bushmaster once I received my prize table Bushmaster from the custom shop...need to keep this one....Bushmasters hab been bery, bery good to me