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Excessive Headspace!

 
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  #8  
Old 12-16-2009, 03:58 PM
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Re: Excessive Headspace!

Johnny S and KDB, unless it was for a dangerous game rifle, I would set headspace as tight as it would go and still chamber unfired brass. I believe it helps with accuracy, brass life and safety. I have had 2 rifles that would not close on a go gage, but would chamber new brass. I left them that way. They never gave any problem of any kind and were very easy to full length resize. The rationale for me is that the Saami spec go gage is long enough to allow any brand of Saami spec ammo to chamber in a gun, so there is already quite a bit of room in a chamber that can just barely take a go gage.

On go and no-go gage lengths, I've never checked the difference in the belted magnum go and no-go gages, (I don't have no-go's) so I don't know what the differential is, but from memory, the headspace gages for shoulder headspaced cartridges that I do have both gages for allow about .006" differential.

I like to use go gages and shims like Chad, and I prefer go gages of the same brand as the reamer. I haven't bought a no-go gage in a long time, but I still use them in Garands and M1-A's.
If either one of them will close on a no-go, It has to be rebarreled. I've swapped out a lot of bolts, and never had one that would make up more than .0015", and that's not enough to bring a gas gun far enough back from maximum headspace. I have the G.I. field test bolt and gage for M1-A's, but never used them.

Sorry about getting long-winded, but headspace is critical, and there is no excuse for getting it wrong. The reason for no-go gages is safety. Excessive headspace can be catastrophic. If you want to crowd a headspace gage, go for tight, not loose. Anything over no-go is unacceptable, and .005"-.010" over no-go is scary. Don't fire another round until it's set back and headspaced properly, whoever you have to get to do it.

Good luck, Tom
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  #9  
Old 12-16-2009, 05:25 PM
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Re: Excessive Headspace!

Thanks for all the responses. I spoke with the gunsmith that did the work and he requested I send it back to the shop so he can fix it and figure out how it managed to leave the shop with improper headspacing.

They typically do very good work and I know they will honor their mistake so I am not going to push the issue. However it was a sobering reminder to trust your gut when something just doesn't seem right.

I am going to have him set the headspace for 1-2 thousandths max.

Thanks again,

-John
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  #10  
Old 12-16-2009, 10:29 PM
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Re: Excessive Headspace!

Quote:
Originally Posted by KDB View Post
Nat and Chad...This is obviously a novice question, but you both are very keen dudes, so I am going to ask anyway.

What is the optimal number for headspace? Is it as close to zero as possible, or is there a need for some minimum tolerance, eg .001-.002 and why? Is it caliber specific or standard across the board?

Thanks in advance.

KB

Pretty much what JE said. It is largely application specific. a rifle that will only be fed carefully hand tailored ammunition can be chambered on the conservative side because of this. A working field gun that will be fed what ever the sporting goods store has on the shelf that weekend will typically get loosened up some. Same thing with breech clearances. Rifles that see a sterile environment can run tighter. Do that with a sniper rifle and it's possible the owner may go home in a bag because his rifle locked up tight on him.
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  #11  
Old 12-17-2009, 01:24 PM
KDB KDB is offline
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Re: Excessive Headspace!

Thanks for the reply. So, if headspace specs is application specific, what is head clearance and how does get determined?

Thanks again.

KB
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  #12  
Old 12-17-2009, 03:36 PM
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Re: Excessive Headspace!

Chad has responded very appropriately. Yes, he is a smart dude.

I have great respect for him. He and I tend to be be a little more on the independent thinker side. Sometimes we catch hell for that.

Have a great holiday and may your rifle return to shoot great.

Nat Lambeth
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  #13  
Old 12-17-2009, 04:36 PM
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Re: Excessive Headspace!

Quote:
Originally Posted by KDB View Post
Thanks for the reply. So, if headspace specs is application specific, what is head clearance and how does get determined?

Thanks again.

KB

While I certainly appreciate Mr. Lampert's kind remarks I'm afraid now I'm going to sound anything but smart. I don't know what head clearance means. I've never heard that one.

If your referring to bolt/breech face then again I base that on the application. A "bench queen" runs tighter (because most customers will have a brain seizure/fit if it's not done that way) where's a working gun gets loosened up so that it'll function in a broader range of conditions.


I'm going to go out on a bit of limb here to try and put some of this into perspective. Let me preface this by plainly stating that IF YOU DON'T KNOW/UNDERSTAND WHAT YOUR DOING STOP IMMEDIATELY AND SEEK THE COUNSEL/GUIDANCE OF AN EXPERT.

There, hopefully that'll thwart the "sea lawyers" out there.

The truth is if a guy was to build a rifle in his basement and screw up the headspace by .005, .010, .015" etc, it's still not quite as big a deal as it's often made out to be. SO LONG as a competent handloader, who understands how to compensate for it, does the handloading work.

You seat that bullet a mile long so that you know beyond the shadow of a doubt that the case head is firmly seated against the bolt face and you fire form the brass. This is nothing more than wildcatting 101. That's all your really doing. If our hypothetical homegrown gunplumber puts the kabosh on a 308 Winchester by gauging it with a NO/GO during chambering by mistake it is not a cardinal sin for him to use that gun. All he's done is create a ".308 Brainfart Improved" and now he has a little extra work to do when loading that first batch of ammunition.

If the shoulder is allowed to blow out to the chamber shoulder nothing really gets upset or hurt because of it.

HERE IS THE PROBLEM:

If this rifle were built for or sold to another person who isn't as careful or who lacks the experience to know what is truly going on then the person who built the rifles is very foolish/reckless and they deserve everything the attorney(s) are going to unleash on him. The reason being is if this poor bastard were to start running factory loaded ammunition through this fuggered/hybrid chamber then it is quite possible/likely going to "sneeze" a cartridge case and send someone to the ER. Ignorance is not bliss when facing the laws of physics.

Make sense?
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Last edited by NesikaChad; 12-17-2009 at 05:45 PM.
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  #14  
Old 12-17-2009, 05:17 PM
KDB KDB is offline
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Re: Excessive Headspace!

I think that the bolt/breach relationship is what I was trying for. I am interested becoming more knowledgeable about the finer details of gunsmithing, but am no machinist. I was reading an discussion on Benchrest Central, in the gunsmithing section, where there was what I would describe as a heated agruement over headspace vs head clearance in regards to a new measuring tool made by Larry Willis.

To make a long story short, it got me thinking about the relationships between chamber, case and bolt and how those dimensions/specifications affect accuracy (if any) and case life. Further inspired by this thread, I thought that I would pose the question.

I guess that I wanted to know if there was a magic number and why. But it seems that there is a +/- tolerance up to saami spec's, depending on application and environment. In terms of case life, more tolerance = more case streach resulting in bumping the shoulder back + degree of tolerance when FL sizing. So, if I am on track in simplistic terms, then do these measurements have any +/- effect on accuracy potential, real or theoritical?

Last edited by KDB; 12-17-2009 at 05:35 PM.
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