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Posted: 12/14/2015 8:33:24 PM EDT
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Hello, I am building my first AR15 from the ground up, started with a striped Spikes Tactical lower. I already have a 10+ year old Bushmaster XM-15 (factory with a few add ons) which works great and a few thousand rounds through it. On my new build I am running into a strange issue with my headspace tests. Both guns are 5.56 barrels but the gauges are .223 Remington (I'm thinking they should work for the 5.56 or am I way off?) In a nutshell the new AR15 build is running a Wilson Combat 18" 1-8 Twist Stainless http://shopwilsoncombat.com/Match-Grade-Barrel-556-NATO-Recon-18-1-8-Twist-Stainless/productinfo/TR-556RC18-18/ and a Spikes Tactical complete bolt assembly http://www.spikestactical.com/bolt-carrier-group-spikes-standard-phosphate-hptmpi-m16-bcg-p-286.html?zenid=75004553ac82ed5a3c267cf70c613daa . The problem is I striped down the bolt (removed extractor and pin) to ensure it wouldn't possibly create a mis-reading during the headspace check. Since these are both virgin parts never fired the bolt will not close with either the GO or the NO GO .223 gauges on this new rifle build. Oddly enough, when I drop these gauges into my used Bushmaster XM-15, that bolt (original Bushmaster, not the new Spikes Tactical) closes on BOTH of them... I would have expected it to NOT close on the NO GO gauge. When I tried to drop in my new Spikes tactical bolt carrier into the used Bushmaster XM-15 it failed to close on both the GO and the NO GO gauge.
So bottom line I am assuming: A) the .223 gauges should NOT be used in 5.56 barrels OR B) the Wilson Combat barrel and the Spikes Tactical bolt are too new and need to be broken in (I read this somewhere but I think thats a bad argument, and from an engineering perspective if its not within tolerances I'm not even going to risk it). |
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A 223 REM 3 gage set will work for a lot of situations.
The 1.4636” gage 223 REM [current] Go, 5.56 NATO Go. The 1.464” gage223 REM [old] Go. The 1.4646” gageUS mil-spec Go. Bolts have a tolerance range of .153” to .156” [bolt face to rear of lugs]. I have seen a number of barrels fail the 1.4636” gage with one bolt and pass with another. The 1.4666” gage223 REM No-go. The 1.4706” gageUS mil-spec No-go. You can use the 1.4696” 223 REM Field gage in place of the US No-go gage for estimating where your headspace may be. The Colt 1.4736” maximum chamber gage is the one you don’t want to fail with a used weapon. I would not accept a barrel that failed the Go gage with a minimum tolerance bolt. Headspace specs are set so a max tolerance round is safe in a minimum tolerance chamber. |
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Quoted:
A 223 REM 3 gage set will work for a lot of situations. The 1.4636” gage 223 REM [current] Go, 5.56 NATO Go. The 1.464” gage223 REM [old] Go. The 1.4646” gageUS mil-spec Go. Bolts have a tolerance range of .153” to .156” [bolt face to rear of lugs]. I have seen a number of barrels fail the 1.4636” gage with one bolt and pass with another. The 1.4666” gage223 REM No-go. The 1.4706” gageUS mil-spec No-go. You can use the 1.4696” 223 REM Field gage in place of the US No-go gage for estimating where your headspace may be. The Colt 1.4736” maximum chamber gage is the one you don’t want to fail with a used weapon. I would not accept a barrel that failed the Go gage with a minimum tolerance bolt. Headspace specs are set so a max tolerance round is safe in a minimum tolerance chamber. WOW! Way over my head! |
| So this gets even crazier, I contacted Wilson Combat support and their official response/position/stance was their machinists and engineering team confirmed their stainless steel barrels will not close on either go or nogo gages by default because they are insanely tight on tolerances. They noted that I need to build the rifle and take it to the range and load a single round from the magazine. The bolt has to close all the way and lock at which point it will fire (because if it doesnt close all the way it will block the hammer so it wouldnt be able to drop on the firing pin thus unable to be fired. They noted it will take a few rounds to break it in. If and only if I cannot get it to close on a round they I should reach out to them to look for next steps (likely sending it back to have it tuned up. It makes sense that a factory new Spikes bolt carrier group and factory new stainless steel barrel would be tight. I tore the whole thing down again and tested the gages (GO nor NOGO) just wont close but its close. I also tried a spent .223 case the problem with that is it sticks out a bit because it expanded already so it doesn't seat all the way down. The bolt closed on it but got stuck and trying to pull the bolt was a bitch, had to use a hammer and cloth to tap the charging handle to break it free. I ordered some snap caps to give them a try too (waiting on them to arrive right now). Some forums and youtube videos say test with a live round, I would never consider throwing a live round down there as a test, too risky even with a pin and everything removed, would be a stupid idea for anyone. So once I try the snap caps fail or no fail I will complete the build and torque to specs. Once at the range I can throw a live round down there to see if it closes all the way and give it a fire. |
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Snap caps cannot be used for your purpose. They are not anywhere near what a cartidge spec is.. Pull a bullet from a loaded round and use the case for a check. Do not attempt to do this without a firing pin in place. You may well lock the gun up with the cam unable to turn the bolt. If you are concerned you can sacrifice a firing pin and grind it short so it can't hit the primer.
Greg |
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Quoted: You cannot use .223 Remington gauges in a 5.56 barrel. All you need is a No-Go gauge in 5.56. You can use an FACTORY loaded round as a Go gauge. Windham Weaponry sells Clymer gauges, and they are running a sale now, too.  |
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Quoted: Snap caps cannot be used for your purpose. They are not anywhere near what a cartidge spec is.. Pull a bullet from a loaded round and use the case for a check. Do not attempt to do this without a firing pin in place. You may well lock the gun up with the cam unable to turn the bolt. If you are concerned you can sacrifice a firing pin and grind it short so it can't hit the primer. Greg I was under the impression that you test headspace with a stripped down bolt with no extractor or ejector in it, and turn it in the barrel extension with finger pressure, not letting it ride in the bolt carrier. |
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Quoted:
I was under the impression that you test headspace with a stripped down bolt with no extractor or ejector in it, and turn it in the barrel extension with finger pressure, not letting it ride in the bolt carrier. Quoted:
Quoted:
Snap caps cannot be used for your purpose. They are not anywhere near what a cartidge spec is.. Pull a bullet from a loaded round and use the case for a check. Do not attempt to do this without a firing pin in place. You may well lock the gun up with the cam unable to turn the bolt. If you are concerned you can sacrifice a firing pin and grind it short so it can't hit the primer. Greg I was under the impression that you test headspace with a stripped down bolt with no extractor or ejector in it, and turn it in the barrel extension with finger pressure, not letting it ride in the bolt carrier. I was referring back to the comment about using a live round. I use a bcg closed by hand and a stripped bolt. I have monkey fingers. Greg |
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