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338 Lapua Headspace Problem?

 
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  #1  
Old 11-23-2009, 02:49 PM
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Location: Arvada, Colorado
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338 Lapua Headspace Problem?

Hi,

I had a custom 338 Lapua built a couple months ago and have seen pressure signs using 90.0grns H1000 powder. Ejector marks on case are very noticable.

A little bit about the rifle, Stiller Tac338 Action, 28" Lilja Barrel 1-10 Twist. Velocity is 2723 average. Bullets are seated to magazine length (Badger M5 BM)

It has been suggested to me by someone on this site, that I might have a headspace problem. I ordered Headspace gauges from PG&T. Sure enough the go gauge goes but so does the no go gauge. The no go gauge was not an easy closing of bolt but it was not hard to close either.

Can someone tell me how much pessure should be used when trying the no go gauge? Once again, I did not force the no go gauge. When I tried closing the bolt it started to cam over pretty easy and when finishing the closing of the bolt it was a little stiffer.

I plan on using .001 brass shims to measure exactly what my headspace is. Look forward to hearing your suggestions.
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Old 11-23-2009, 07:01 PM
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Re: 338 Lapua Headspace Problem?

When using headspace gauges you should strip the bolt(fire-pin, ejector, extractor.) That way you can FEEL what is happening. Using pressure to close the bolt on a hardened gauge is not somthing you should do. A couple of problems that can happen; unlubed lugs may gall from the pressure between the 2 surfaces, as the bolt is forced. Or the gauge may mar the shoulder of the chamber, under certain circumstances. You should use no pressure to close the bolt when it is stripped, it will basically flip flop very easily because there are no springs or a cocking piece to cam. Just let gravity take the handle down, or at most pinky pressure.

A couple things on pressure, Shawn a few months back brought up some info on newer runs of H100 being a little faster, some members here have found this to be the case, and it may be affecting your loads. Seating jammed or very close to the lands can increase pressure. Do you know what the lead length is in your chamber? Some barrels do not run as fast as others, and if your very early in round count your barrel may speed up with some use.
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Old 11-23-2009, 08:25 PM
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Location: White City, Saskatchewan
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Re: 338 Lapua Headspace Problem?

My stiller 338 (338 LAI) leaves an ejector pin mark no matter how low of a load I put in it. After fire forming I was only loading a maximum load of US869 for the straight 338 Lapua and it was doing it. It even did it with the fire forming loads. I plan on contacting Jerry about it again!!! I am only neck sizing so head space is not the issue. My ejector pin is even stuck now that enough brass has ended up in it.
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Old 11-25-2009, 03:47 PM
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Re: 338 Lapua Headspace Problem?

Cowboy,

Sorry I have not replied sooner, have been helping my son get ready for his guided Mule Deer hunt.

I took your advise and completely stripped the bolt and cleaned everything. When trying the Go pin the bolt dropped freely. I did the same thing with the No Go gauge and it also dropped freely.

I finally got my .001 shim stock. I took one .001 shim applied a very small amount of grease (TW25B Kleen Bore Grease) layed it on the bolt face and tried the No Go gauge again. It too closed freely. I added one more shim for a total of .002 and the bolt did not close.

I called PTG and they said the tolerance between the Go & No Go is .004 This is telling me that I have .005 headspace.

On a side note, when I took the ejector pin out of the bolt I noticed the material around the ejector hole was raised above the bolt face. It looked to me like the ejector pin hole had been drilled / reamed after the bolt face was machined.

I believe that the excessive headspace and burr around ejector is what I have been seening as pressure signs.

Ray
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Old 11-25-2009, 06:06 PM
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Re: 338 Lapua Headspace Problem?

I would hope that the smith would correct the problem for you, It's not that difficult to get a barrel to headspace within .002 of the go gauge.

If he won't and you decide to live with it just set up your dies so you don't push the shoulder back any further than neccesary.

If he will set the barrel back for you, have him FIRST take a skim/truing cut on the bolt face to get rid of your displaced ejector button hole.
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  #6  
Old 11-25-2009, 10:13 PM
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Re: 338 Lapua Headspace Problem?

Thanks Jim,

I have 200 once fired Lapua cases. If I understand you correctly, I should be able to control headspace now that the cases have been fire formed to my chamber? I use Redding Competition bushing dies and prefer neck sizing only. If I only bump the shoulder back when necessary, does the headspace even matter at this point?

I deburred the ejector hole with 320-400 grit sandpaper and it is fine now. I would prefer to leave the rifle as is if possible. It is a shooter and got it where I want it but do not want to sacrifice quality either. I believe the smith did a heck of a nice job on this rig and the burr on the ejector contributed to my headspace problem. As I said I have run 200+ cases thru this action already. Who knows how big the burr was to start with.

Ray
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  #7  
Old 11-25-2009, 10:27 PM
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Re: 338 Lapua Headspace Problem?

Ray as long as you size accordingly everything will be fine. The problem with excessive headspace is when the brass is allowed to stretch and then FL resized a number of times. This will cause the web area to get worked overtime and eventually seperate. Continue as you have been and when the shoulder needs to be bumped, give it just a wee bit so it will chamber freely and not over set the shoulder.
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