AR-15 - What Bolt Carrier does this upper take?

[OCSlacker]

Okay, so I have this AR upper, and I may know how to shoot them and build the lower, but I am a blundering idiot when comes to the upper. My upper is sans bolt & carrier. I need to purchase one, but I have no clue what one to purchase for it. I have an olympic arms ar (of unknown spec) and the bolt & carrier from that will not seat inside this upper. It's way too tight. I'm looking for what spec and/or a bolt that will fit this.

 

[SCARCQB]

Any Mil- Spec Bolt Group should fit that upper. It also looks that you may have a 14.5" upper. If you do not have an SBR or MG lower. Make sure that the flash hider is pinned/ welded on permanently and with that, it overall Barrel length is 16" min.

Or else, you break NFA laws ( short barreled rifles, bbl < 16")

 

[razorV23]

Is your gas tube lined up straight from the front sight?

 

[wilcam47]

gas tube might be sticking out too far...or wrong length

 

[straightsilver3]

LMT BCM Spikes Nib all good BCG's Search the web about Oly's being out of spec Not the best name in the business

 

[OCSlacker]

Any Mil- Spec Bolt Group should fit that upper. It also looks that you may have a 14.5" upper. If you do not have an SBR or MG lower. Make sure that the flash hider is pinned/ welded on permanently and with that, it overall Barrel length is 16" min.

Or else, you break NFA laws ( short barreled rifles, bbl < 16")

Good point, but it is a 16" upper. It's the same length as my OA upper with a pinned/welded Noveske Flash Suppressor. If the flash hider was removable, I would think it would be a no go though. You believe it to be a mil spec though? Which is excellent, might have solved my issue then.

Is your gas tube lined up straight from the front sight?

gas tube might be sticking out too far...or wrong length

The gas tube does extend the correct distance (putting it up against a 16" OA upper for comparison).

 

[303_enfield]

Turn the upper upside down and place the Oly bolt in it slowly. What do you see? Is the bolt binding on the receiver? Gas tube lined up?

Who built the upper? If it's F'd up I can loan you the tools to fix it or tear it down for you. In OC six days out of seven

Receiver and barrel have Colt forge marks. Any .223/5.56mm BCG "should" fit. PM me if you need the tools or help.

 

[smokey]

Hmm, where'd ya get that beat up thing? You may want to have the headspace checked on that and have it looked over by a competent smith if a oly bcg won't seat inside it. Who knows if someone clamped it in a vice without a vice block and squeezed it too much, or if the extension is messed up, or whatever. As is, ure gas tube looks funky.

 

[OCSlacker]

Well I might need to change the upper itself. The bolt is getting stuck towards the back end of the upper. Past that point it slide it perfectly fine, but it can't be racked as it'll get stuck on the way back! At least it's not bad, a mere $100 part to change out.

 

[RW2111]

how far back form the chamber is it getting stuck

 

[wilcam47]

gas rings might be getting hung up?

 

[Forest]

Well I might need to change the upper itself. The bolt is getting stuck towards the back end of the upper. Past that point it slide it perfectly fine, but it can't be racked as it'll get stuck on the way back! At least it's not bad, a mere $100 part to change out.

is it getting stuck while the upper is mounted in a lower, or does it stick with the upper out of the lower.

If it's the former then it may be a receiver extension issue.

 

[OCSlacker]

The front half of the bcg is getting stuck in the back half of the upper (regardless of it being mounted to a lower or not). The upper has been through hell and back, so I have no problem getting a new upper. I bought one through Del-Ton for about $83. Can't beat that.

 

[zoostation]

sounds like something is out of spec to me, probably the upper itself. I've seen/experienced this problem myself with lower end uppers myself in the past, though it usually isn't so bad that it manifests itself before you mate the upper and lower and try to cycle. Oly used to make a lot of parts by casting instead of forging too which doesn't help. Really any decent 5.56/.223 BCG should work. I would see if you could borrow another BCG and see if it worked before going to the trouble of tearing down the assembly and replacing the upper though. In any case the barrel is a Colt and worth saving if it isn't shot out. You would pay 250-300 bucks for a new Colt M4 barrel. With me not knowing anything about the upper or its history I would suggest having the headspace checked as well.