Help: First AR build - bolt will not go into battery

[choochoo]

After assembling the AR upper, I realized the bolt would not go all the way forward. Unfortunately, I didn't check the barrel prior to assembly. after disassembling the upper, I tried inserting the bolt (correctly aligned) into the barrel extension and it will not turn all the way to full lockup. The bolt lugs are hitting the back side of the barrel extension. I assume my bolt is fine, because it works on my other upper, which was purchased fully assembled.

Any ideas? Can this be fixed? should I consult a local gunsmith?

any help is greatly appreciated. Thanks.

[Coffeeandgunsandammo]

Any pictures?

Sent from my LM-Q710(FGN) using Tapatalk

[instaramen]

Sounds like a headspace issue. Is this a new bolt or did it come with a pre-assembled upper? A company usually headspace a bolt and upper before they ship which is why it's ready for shooting. If you're building a new upper, you need to headspace the bolt with that upper using go/no go gauges. If you're having doubts, contact randall at ar15barrels, he's a calguns member and reputable gunsmith in socal.

[ar15barrels]

After assembling the AR upper, I realized the bolt would not go all the way forward. Unfortunately, I didn't check the barrel prior to assembly. after disassembling the upper, I tried inserting the bolt (correctly aligned) into the barrel extension and it will not turn all the way to full lockup. The bolt lugs are hitting the back side of the barrel extension. I assume my bolt is fine, because it works on my other upper, which was purchased fully assembled.

Any ideas? Can this be fixed? should I consult a local gunsmith?

any help is greatly appreciated. Thanks.

It's normal for the bolt lugs to engage the extension's lugs.
That's how the system is designed to work.

Are you having the problem WITH ammo or WITHOUT ammo being involved?

Assume nothing.
Gauge everything.

[choochoo]

Any pictures?

I'll try to post some tonight.

Sounds like a headspace issue. Is this a new bolt or did it come with a pre-assembled upper? A company usually headspace a bolt and upper before they ship which is why it's ready for shooting. If you're building a new upper, you need to headspace the bolt with that upper using go/no go gauges. If you're having doubts, contact randall at ar15barrels, he's a calguns member and reputable gunsmith in socal.

The bolt is from toolcraft, the upper that I normally use it on is a PSA wylde and it works fine.

I'll go order some go/no go gauges.

It's normal for the bolt lugs to engage the extension's lugs.
That's how the system is designed to work.

Are you having the problem WITH ammo or WITHOUT ammo being involved?

Assume nothing.
Gauge everything.

the problem is without ammo. the bolt wouldn't go into battery, even pushing on the forward assist. I could get the bolt into battery with a couple of whacks from a rubber mallet. I disassembled the upper to see if I could get a better look of where the lugs were contacting the barrel extension. But, I can't really see. I can see some metal on metal contact on the back of the bolt lugs.

[ar15barrels]

the problem is without ammo. the bolt wouldn't go into battery, even pushing on the forward assist. I could get the bolt into battery with a couple of whacks from a rubber mallet. I disassembled the upper to see if I could get a better look of where the lugs were contacting the barrel extension. But, I can't really see. I can see some metal on metal contact on the back of the bolt lugs.

Measure the LENGTH of the bolt lugs.
Should be around 0.279" to 0.281".

A bolt with the correct length should have about 0.010" of front-back movement within the barrel extension without any headspace gauges in the chamber.

[choochoo]

ok, will do. if the headspace is too short, what are my options for fixing it?

[instaramen]

ok, will do. if the headspace is too short, what are my options for fixing it?

1) find another bolt that will go into battery without forcing it
2) get a new barrel
3) ream the chamber until bolt fits, wouldn't recommend for chrome line barrels

[ar15barrels]

ok, will do. if the headspace is too short, what are my options for fixing it?

Depends on the details of the barrel.
Bolt fitting or NOT fitting is NOT a headspace problem.
Bolt NOT fitting is an endspace problem.
An endspace problem could be from a bad BOLT or from a bad BARREL.
In the case of new parts, let the manufacturer or the dealer handle it.

[choochoo]

The endspace is in the barrel extension, correct?

[ar15barrels]

The endspace is in the barrel extension, correct?

The endspace is the space between the back of the barrel and the front of the lugs inside the extension.
When endspace is off, it's normally the barrel that was machined wrong.
I have yet to see an extension that was out of spec other than one that was not hardened.

[choochoo]

bolt lugs - 0.2795"


will not rotate beyond this point


the bolt lugs are coming into contact with the barrel extension

[Devilock04]

I built a second upper for my AR-308 using a no name bolt that I got what I thought was a good deal on. The bolt would not go fully into battery and would stick closed with dummy rounds. I would have to mortar it to get the dummy rounds out.

I narrowed it down to the bolt being out of spec by trying the JP Rifles match grade bolt out of my first upper. If you know someone else with an AR, see if their bolt will close.

[ar15barrels]

bolt lugs - 0.2795"


will not rotate beyond this point


the bolt lugs are coming into contact with the barrel extension

Barrel is bad.

[emarkham]

OP, are you absolutely certain you are not getting interference from gas tube misalignment?

Remove the bolt and slide the bolt carrier back and forth in the upper receiver using finger pressure. Is it stiff or binding?