Headspacing questions

I'm nearing the end of my 450 Bushmaster build and I need an extra opinion regarding headspacing. I have proper gauges on the way but in the mean time I wanted to get everything together in it's proper place when I was working on my stock so I went ahead and set it up with an unfired factory round.

Here's where I'm at currently with everything tightened up,

Bolt closes on unfired factory round without resistance
Bolt closes with very slight pressure with .002" brass shim stock
Bolt engages but won't fully close on .003" brass shim
Bolt will not move on .004" brass shim

My question is since from what I've read this seems ideal would you guys recommend me to disassemble and completely start over when the gauges get here? Or if it closes on the go but doesn't on no go just leave it alone? I'm trying to minimize the amount of wrenching that I have to do on the new cerakote but I also want to make sure it's right.

FWIW I don't reload so most likely factory ammo is all that will ever be fired from this rifle.

I don't care what anyone says.Wait for the gage and set it right to sammi standards and factory ammo will fit perfect and safely.

Were it me...if it passes the go/no-go as is, your good to go. Why risk damaging a finish if not needed. Just my 2 pennies worth.

Ok, but once the gauges get here and If I test them in it where it is currently set up and the bolt closes on the go gauge but doesn't on the no go can I assume that it is correct or should I loosen it back up and start over with the gauges?

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Originally Posted by COplains

Were it me...if it passes the go/no-go as is, your good to go. Why risk damaging a finish if not needed. Just my 2 pennies worth.

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Answered my question while I was typing. Thanks!

I did a similar process with mine. Just used the go/no go to double check. I would not start over. I would just throw both gauges in there, double check, and go shoot.

if the gauges are on the way I would wait and use the gauges. that is my opinion.

Bruce

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Originally Posted by maroberson

If I test them in it where it is currently set up and the bolt closes on the go gauge but doesn't on the no go can I assume that it is correct

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that's what your going for.

starting over really won't get you any closer, but I wouldn't shoot it until you check it with the gauges.

Got the answers that I wanted to hear. Thanks for the input guys.

This is why the gages were 'introduced' in the first place. Think about an official language versus dialects....they can get you by but they are not the 'authority'. Checking with the gages will give you the peace of mind you need to confidently pull the trigger.

I would not recommend using UN-fired case to check headspace. Sounds dangerous to me.

Ok, the gauges came in today which leads me to my next problem. I initially tried the go gauge in the rifle and to would not close at all so I preceded to take it apart and set it up with the gauges.
I got it to close on the go and not on the no go but I noticed that I could not get the gauges to extract. Thinking that the gauges were not getting under the extractor I took the extractor out and verified that the it still fit the same. I then checked how the gauge fit into the opening in the bolt head and found the source of the apparent problem.
The gauges that I got are slightly larger in diameter and will not flush up to the bolt face. The rim of the gauge fits into the beveled part of the opening but stops there and will not go all of the way back to the face. The factory ammo that I have will obviously sit all of the way down to the bolt face.

Is this normal for a gauge to be slightly larger in diameter than factory brass? Should the gauge sit flush with the bolt face?


Thanks in advance

The gauge should sit flush on the bolt face.

That's what I figured. I guess I got the wrong gauges. They told me they have standard and ar-15 versions. I got the standard. I'm not sure of the difference but if that is the standard diameter of the 450 BM gauges then I'm not sure any of them will work.

I had the same problem when I rented my gauges for 450BM. I forget now which ones were which but they sent me the "other" gauges and everything was good. It's a little disappointing being that close only to have to wait a little longer. Hang in there, I'm sure you'll solve the problem with the other gauges.

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Originally Posted by clintsrv

I had the same problem when I rented my gauges for 450BM. I forget now which ones were which but they sent me the "other" gauges and everything was good. It's a little disappointing being that close only to have to wait a little longer. Hang in there, I'm sure you'll solve the problem with the other gauges.

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Thanks for the reassurance. I'm going to call them Tuesday and try to get the other set. You're right, it is kinda disappointing but this is my first attempt at doing this and now realize I've done things kinda backwards but I've certainly learned a lot and It'll be worth it in the long run.