Expanded case head

[josh.rizzo]

Someone asked for chamber dimensions... Despite my love of being precise i have no way of measuring my chamber dimensions that I can think of. Any tips on that? Its the .308WIN chambering of this model: http://www.savagearms.com/firearms/model/10FCPHS if that helps.

Its awesome to see so many people genuinely interested in solving this problem. You guys are awesome and I'm glad I joined this forum!

 

[Syncrowave]

I'm just now getting back into rifle reloading after being away from it for about 30 years. I was just re-reading my 1979 Speer reloading manual, specifically a 1963 piece written by Jack O'Connor.

Jack writes:

"The first sign of [excessive] pressure our boy should look for is the sticking case...His next sign is the primer leak. He will notice that the primer appears dark around the edges...If the whole primer has flattened against the bolt face and filled the primer pocket to the edges, pressure is probably too high. Likewise it is probably too high if the primer metal is cratered up around the firing pin indentation. Any measurable expansion of the case at the rim shows pressures that are much too high."

Despite my love of being precise i have no way of measuring my chamber dimensions that I can think of. Any tips on that?

Measure a fire-formed case (before resizing)? That's the best I can think of...

 

[josh.rizzo]

You have leaking around the primers, and case heads are expanded, right?
If so, they're not blown primers.
CCIs and WLRs are different thickness, and affecting load pressures a bit(not much), but really nothing more than distraction to the issue.

4 of them were blown out completely but most just showed leakage as shown in the link from 243winxb (http://s338.photobucket.com/user/joe1944usa/library/Firearms%20%20and%20%20Reloading/Primer%20Gas%20Leak)

I switched t a larger shell holder and got primers into 18/20 of them (2 would not hold a primer at all). They definitely felt loose though, judging from the fell of my Lee hand priming tool. This is using the CCI200s.

 

[josh.rizzo]

I'm just now getting back into rifle reloading after being away from it for about 30 years. I was just re-reading my 1979 Speer reloading manual, specifically a 1963 piece written by Jack O'Connor.

Jack writes:

"The first sign of [excessive] pressure our boy should look for is the sticking case...His next sign is the primer leak. He will notice that the primer appears dark around the edges...If the whole primer has flattened against the bolt face and filled the primer pocket to the edges, pressure is probably too high. Likewise it is probably too high if the primer metal is cratered up around the firing pin indentation. Any measurable expansion of the case at the rim shows pressures that are much too high."

Funny enough, NONE of them showed flattening or felt stuck - just leakage. They did have some pretty good extractor marks on them though. https://www.dropbox.com/s/d143gd2fw5oy5lw/2014-01-03%2020.27.05.jpg The scratches are from trying to jam it into the shell holder (it did NOT come out of the gun that way).

 

[Syncrowave]

Looks like the brass flowed into the ejector plunger cutout on bolt face maybe (circular mark on head by "L" in LAPUA)?

If so, that's a sign of way high pressure I think.

 

[Shynloco]

Josh,
I'm not sure this is relevant, but I recall a old timer (been reloading for over 60 yrs) once told me that a method he uses for checking for "excessive pressure" is to remove the spent primers and mic them. If they are more than .002 larger in either height or width, you have "excessive pressure" like it or not. I've found that when I've used this method, I've also found some very minor cupping as well that is NOT necessarily as pronounced as some using the "fingernail feel across the top" approach can show you.

 

[scott_at_vortex]

What is the measurement of the web diameter on a virgin piece of brass? fired,but no pressure? and finally one of blown primer piece's?

The virgin piece should have a measurement around .469"

 

[josh.rizzo]

What is the measurement of the web diameter on a virgin piece of brass? fired,but no pressure? and finally one of blown primer piece's?

The virgin piece should have a measurement around .469"

I don't have any unfired brass at the moment, but ALL my brass measures .470"-.471" on the case rim and base of the body, so that seems right. The extractor groove is what changed from .405" to .410" on the bad cases. Seems to be the only affected measurement.

 

[itchyTF]

Chamber dimensions? Try a chamber cast with Cerrosafe.

 

[Syncrowave]

Any chance somebody mistakenly annealed the entire cases, instead of just the neck/shoulder area, leaving some of them with "soft heads" that expanded...?

Just throwin out ideas here...

 

[josh.rizzo]

Any chance somebody mistakenly annealed the entire cases, instead of just the neck/shoulder area, leaving some of them with "soft heads" that expanded...?

Just throwin out ideas here...

Good call, but no. They were brand new from Lapua and I could tell the neck was annealed in the proper place from the color.

 

[Old Navy]

Blown primers that are weak and get pierced and etch the bolt face is a problem but that should not cause a pressure problem that expand the case head – two different problems.

+1 Later! Frank