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Checking head space with barrel installed


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I made a tool for checking Head Space with the barrel installed in the upper, I don't like using the bolt carrier to check head space because I think it gives to much mechanical advantage rotating the bolt. The tool I made is for AR 15's but it will work on LR 10/308's as well, its a little sloppy in a LR bolt but it works. the aluminum piece that goes in the cam pin hole is loose in the bigger bolt and the piece that centers the tool in the upper is also loose but you get a feel for it, If I can get access to a lathe I am going to make one for the LR 10 platform...






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Checking headspace with a barrel installed are exactly what headspace gauges do....  Mounted barrel, installed bolt - headspace gauges tell you if you're good, or not good.  In-service weapons, and the Field gauge, are few and far between.. .

What are you accomplishing here, with this device?... 

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It just makes it easier to hold the bolt, I use it with head space gauges. Like I said I don't like to use the carrier because you have no real feel when you just push the carrier in, with this I can feel the bolt turn and feel how tight or loose it is.  I have a couple of cheaper LR 308 barrels that when checked bare [uninstalled] and turning the bolt by hand they will almost close on a NOGO [1.634"], but when installed and torqued to 40-60 foot pounds and checked with a carrier they will close on the NOGO but with my tool you would have to turn it pretty hard to get it to close on the NOGO. All testing done with a stripped bolt.


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So you are taking the bolt carrier out of the equation. I would be MORE interested in the results of the head space measurement in the configuration I would be firing the rifle. Doesn't but almost closes on no go gauge my way. But closes on no go gauge when I measure like most people. Just doesn't sound safe to me.

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Closing on a NOGO is not the end of all things, closing on a FIELD yes. The biggest problem closing on a NOGO is if you are reloading ammo for several different guns, you need to keep the brass from the rifle that will close on a NG separate form brass from other guns with tighter chambers.  Two barrels I have are a brand new BA barrel the other is a ELD? barrel I got for $40 from a guy that never installed it, I have tried 3 different bolts and they are all the pretty much the same, they will close on a NOGO [1.634"] but not on a 1.635" gauge. I would like to try them with a NIB bolt and see if the coating thickness is enough to make them pass the NOGO test, I have never used one so I don't know much about then them, do any body make longer bolts for the LR 308 to help with head space?


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2 hours ago, earthquake said:

Closing on a NOGO is not the end of all things, closing on a FIELD yes.

Only if it's on an in-service weapon - not a new build.  The Field gauge is only used on an in-service weapon, and no other time.

A Field gauge should never be used to judge a new weapon, or it's headspace condition. 

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