No go?

Discussion about 5.56mm ARs

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triggerman300
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No go?

Post by triggerman300 »

Recently got a good price on an 18" SPR barrel for my 5.56 upper. It's not here yet but broke the gun down awhile and cleaned everything real good. I figured I'd get some headspace gages and check the new barrel with my bolt,just to be sure. I thought I'd check my old barrel,just for grins. I stripped the bolt,dropped the go gage in and the bolt will spin when fully inserted. Only problem is it does the same with the no-go gage. I've got a couple hundred rounds through the old bolt/barrel combo and never had a problem,other than it not being real accurate. Now I'm curious how it would do with a field gage. The original barrel and bolt were bought seperately and HS was never checked.
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A-Game
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Re: No go?

Post by A-Game »

ARs are self head spaced because there is nothing to adjust. A tight chamber can only be reamed.
There are foreign pin protrusion gages that may be more useful.

Any in spec bolt will mate up to any in spec barrel.
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triggerman300
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Re: No go?

Post by triggerman300 »

This is the opposite of tight. I guess I'd have to try some different bolts to correct it. Hope I have better luck with the new barrel.
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bangbangping
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Re: No go?

Post by bangbangping »

That's why you should never check headspace. It only causes you grief and needless worry. :lol:
I kid, of course. Do you reload or shoot factory ammo?
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r.tenorio671
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Re: No go?

Post by r.tenorio671 »

triggerman300 wrote:Recently got a good price on an 18" SPR barrel for my 5.56 upper. It's not here yet but broke the gun down awhile and cleaned everything real good. I figured I'd get some headspace gages and check the new barrel with my bolt,just to be sure. I thought I'd check my old barrel,just for grins. I stripped the bolt,dropped the go gage in and the bolt will spin when fully inserted. Only problem is it does the same with the no-go gage. I've got a couple hundred rounds through the old bolt/barrel combo and never had a problem,other than it not being real accurate. Now I'm curious how it would do with a field gage. The original barrel and bolt were bought seperately and HS was never checked.
.....more than a single thing can influence the results of checking HS with gauges. If your NO GO is allowing the bolt to fully seat and rotate into a locked position the "possible" causes can be (in no particular order) assuming ammo's casing is to spec:

1. Barrel chamber erosion in area of shoulder(typical after high round counts)
2. Chamber cut out of spec (depth/length)
3. Barrel extension lug wear/out of spec
4. Barrel extension face wear/out of spec
5. Bolt lug wear/out of spec (front to rear dimensions)
6. BCG cam pin channel wear/out of spec
7. Cam pin wear/out of spec
8. BCG face wear/out of spec

...due the minimal measurement differences between the 3 typical gauges used, each of the referenced points listed above can allow/disallow the movement of the bolt accordingly. Items 5-8 can be readily resolved by parts replacement/swapping and sometimes resolve 3 & 4 as well. Items 1 & 2 are a little more involved, but doable.
triggerman300
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Re: No go?

Post by triggerman300 »

I shoot mostly reloads. I was checking with the barrel uninstalled and a stripped bolt. BCG wouldn't be a factor,only a couple hundred rounds through this barrel. Erosion shouldn't be either. Probably bolt problem. If I have the same problem w/new barrel I'll have to get some new bolts.
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