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Excessive Headspace!

 
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  #1  
Old 12-15-2009, 02:36 PM
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Join Date: Oct 2009
Location: Northern Alberta
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Excessive Headspace!

So here's the deal, I have excessive headspace on my .338 Lapua (Timeberwofl Action). I confirmed this with a no-go gauge and some .003 paper. The best I can figure it is somewhere between .005" and .010" over the no-go gauge tolerance. This explains alot of problems I have been having including:

-Failure to extract un-fireformed brass. This was my first indicator but the gunsmith assured me the headspace was fine and opened up the extracotr claw instead.
-Excessive force required to full length size brass.
-Near case head seperation after firing full length sized brass.

The accuracy has been erratic but I'm not sure if this is attributable to the headspace or not as most of the rounds I fired were necksized only.

Anyhow for all the gunsmiths on the board could this have caused any damage to the action (It's been fired around 200 times)? I only want to know because I would like to know how far I should be going with the gunsmith on this one.

Another questions is how much headspace should there be for optimum function and accuracy? The intent for the rifle is a long range hunter in conditions which don't require a "loose" chamber so accuracy is primary.

Thanks,

-John
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Last edited by Johnny5; 12-15-2009 at 04:22 PM.
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  #2  
Old 12-15-2009, 03:26 PM
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Location: South Dakota
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Re: Excessive Headspace!

Everything needs to be checked, double checked, and then checked again.

It's the only way to know.

Chad
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Last edited by NesikaChad; 12-15-2009 at 03:31 PM.
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  #3  
Old 12-15-2009, 04:27 PM
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Join Date: Oct 2009
Location: Northern Alberta
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Re: Excessive Headspace!

I contacted PGW to ask whether or not that would damage the action or bolt and they assured me the action was plenty strong enough to take that with no damage which puts my mind at ease some. Still ticked that alot of good and very expensive brass was ruined and the chamber needs to be re-done but at least I'm not screwed on the action.

Can anyone suggest what the optimum headspace should be. The Kiff gauges give a .005" tolerance between the go and no-go, is there some kind of sweet spot in there or anywhere in that range is good?

-John
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Old 12-15-2009, 06:57 PM
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Location: South Dakota
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Re: Excessive Headspace!

Here's what I do:

I don't own any NO GO gauges. Not one.

I buy all my GO gauges from PTG.

I have a spool of .001" shim stock made by Starret.

Strip the bolt of anything that has a spring or plunger. Drop in your gauge and allow the bolt to go home. It should rotate into battery under the weight of gravity.

Now start cutting little postage stamps of shim stock and sticking them to the bolt face with a dab of grease. Keep stacking until the bolt handle no longer wants to rotate.

The way I refer to this dimension is "GO plus whatever the number of shims are."

This can be a very valuable tool to a guy if he starts doing this from day one, especially with a "boomer" magnum.

Say on day one of receiving your rifle you do this and you come up with "GO+.002" for a headspace dimension. Now a thousand rounds later you check and it's changed to "GO+.006". Obviously something has moved. It could be the lugs have peened back, something is wearing, whatever. You at least had a starting point that a GO/NO GO can't provide by themselves.

Last, it allows a guy to set his dies up right at the bench. If you measure your chamber and then replicate this by running your die to the same point you should have a more accurate representation of your chamber's depth so that you don't push the shoulder back further than it needs to be. Just plop the gauge in the shell holder with the shims in place and screw the die to the gauge. Perhaps remove a shim or two so that things chamber easily.

That's my way.

Chad
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  #5  
Old 12-15-2009, 09:08 PM
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Join Date: Dec 2007
Location: Youngsville, NC
Posts: 374
Re: Excessive Headspace!

Dave Kiff is in the business of making custom tooling. He will make reamers and gauges to almost any specification.

SAAMI spec Go and No Go gauges differ by .0035" not .006.

We all know that we fire form to make wildcats. We also know that outside SAAMI specs things can get dangerous very quickly.

I would highly recomend you have a reputable gunsmith check your gun.

When shooting magnums at the top end of the presure grid there is no room for error.

I agree that what Chad Dixon said about using shims works. However, if you are working in a shop that has liability insurance, they require the use of "steel gauges, both Go and No Go." It takes any guess work out of the equation.

Nat Lambeth
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  #6  
Old 12-16-2009, 02:04 PM
KDB KDB is offline
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Location: Arkansas Delta
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Re: Excessive Headspace!

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
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  #7  
Old 12-16-2009, 03:02 PM
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Join Date: Jul 2004
Location: Texas
Posts: 5,383
Re: Excessive Headspace!

Quote:
Originally Posted by Johnny5 View Post
So here's the deal, I have excessive headspace on my .338 Lapua (Timeberwofl Action). I confirmed this with a no-go gauge and some .003 paper. The best I can figure it is somewhere between .005" and .010" over the no-go gauge tolerance. This explains alot of problems I have been having including:

-Failure to extract un-fireformed brass. This was my first indicator but the gunsmith assured me the headspace was fine and opened up the extracotr claw instead.
-Excessive force required to full length size brass.
-Near case head seperation after firing full length sized brass.

The accuracy has been erratic but I'm not sure if this is attributable to the headspace or not as most of the rounds I fired were necksized only.

Anyhow for all the gunsmiths on the board could this have caused any damage to the action (It's been fired around 200 times)? I only want to know because I would like to know how far I should be going with the gunsmith on this one.

Another questions is how much headspace should there be for optimum function and accuracy? The intent for the rifle is a long range hunter in conditions which don't require a "loose" chamber so accuracy is primary.

Thanks,

-John
The amount of head space will vary depending on the rifles use.

I would recomend a max of .003 for factory rifles that only shoot factory ammo because it
varies in size and if you don,t reload brass is not a problem.

For the accuracy buff I will normally set head space less than .0015.

And for the belted cases I like .0005 to minimize brass stretch at the first firing.

As a general rule I would say that .001 to .003 is the best range for head space and then
minimum sizing of reloads.

The only thing I would recomend other than getting the head space issue resolved is to toss
the brass that you fired in it because with excessive head space case head separations
are common due to stretching the web area of the brass.

Hope this helps

J E CUSTOM
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