Competition chambers

K

kchw7gsv

Guest
In chambering a competition benchrest rifle much has been written and discussed about not “just” using go/ no go gauges. I can understand the stacked-up problems that could arise using SAMMI specs for a chamber and then hoping that my competition sizing die is perfectly matched.
My question: If a barrel was chambered using SAMMI specs- go/ no-go gauges- probably not a crush fit on a virgin case, then the brass was normally fire-formed, and a custom sizing die was purchased to match the cases, what if anything would be left on the table?

Kurt H.
 
Kurt, just about any "Benchrest Chamber" can be considered a custom item. Heck, I don't have a clue what a SAMMI spec guage would even fit like in my chambers, if at all. I decided years ago that was what I wanted, and as you have noted, I have dies that make everything correct after fireforming. I have a headspace gauge that I made so I can duplicate my chambers every time, time after time.

This is another one of those senarios where a little common sense goes a long way. Fireform your cases, and, using a die that is correct for your chamber, (as you noted), set it up so that you are bumping your shoulders about .001 or so, and that's about it.

Well, not quite, there is that "tune thing" and all of that, but that is another book.......jackie
 
Going a little closer to finished brass size can help some with primer pocket life. Most competition rifles are shot on the warm side (load wise), so they can sometimes be hard on primer pockets. Other than that and what was mentioned above, no, you're not missing out on much.

You didn't mention what round you're chambering for. Depending on what it is, there may not be such a thing as a SAMMI spec for it. I don't think there is such a thing for round like the PPC or 6BR, amongst many others.
 
If fired brass (preferably well used, and work hardened) is available, for whatever caliber you are planning on building, you might consider buying your die, sizing some cases, an ordering your chamber reamer for the fit that you want.

As far as improving longitudinal fit for fire forming goes, you can always expand necks and form a false shoulder that gives you the fit that you want/need. I have not found that this is necessary for my PPC.
 
Thanks for the replys. I am talking 6ppc. I just needed a little re-inforcement in this area.

Thanks again,

Kurt H.
 
Kurt, I don't think that I am going out on a limb by saying that many shooters overthink this entire thing.

What in reality is a simple task to us is protrayed by many as shrouded in mystery, clouded by uncertainty, and beyond mere mortals thought proccess. But, as I said before, the instituting of a little common sense into the whole senario goes a long way in stripping away the very things that scare us the most........jackie
 
jackie schmidt;619500 What in reality is a simple task to us is protrayed by many as shrouded in mystery said:
Boy, you got that right!! :) As Pogo would say: "We have met the enemy and it is us."
Click to expand...
 
First of all, understand that I am one of the people referred to as "overthinking this stuff."

There are some things I will disagree with in the above statements.

#1, minimum dimension chambers WILL NOT help to contain your primer pockets. I've got chambers that run the gamut from tight to loose in 5 common chamberings and can state from actual testing that you CANNOT contain caseheads using either the chamber or the boltface recess.

#2, fireforming using sloppy end clearance WILL result in crooked brass. This is specifically why some folks will always advocate greasing cases. Itr's the ONLY reason for greasing cases.

Many folks disregard the fact that we Stand on the Shoulders of Giants, that pioneers have gone before us and paved the way, that a lot of what we do has been bought and paid for by others.

"Overthink" my achin' ass........ accuracy is hard. What makes me laff is when the "doers" come back after several years and preach what they scoffed at prior. I see this a lot.

go out, spend the money and find out for yourself.

Or lissen to the thinkers.

BTW, where did you find SAAMI specs for the PPC?

al
 
Al, I wasn't thinking of you at all. You generally keep to the practical side of things.

As for the SAAMI PPC, that probably goes back to the originol Sakos and Rugers that were Factory Chambered for the 6PPC. That would be my best guess........jackie
 
Why Thanks Jackie ;)

From someone who actually DOES try stuff and experiment I'll take that as a real compliment.

I'm a little gunshy in this area. I can't count the emails, posts and PMs from guys insisting that I make it all too complicated!

As one who's owned Ruger #1's, Ruger 77's and a Sako in "6PPC USA" I'll suggest one stay away from SAAMI Spec if this is what it's based on.

Jim Borden taught me how to headspace the PPC and I can state as fact that if you get one of his chambers and buy his prep'd cases they'll form up straight and true. Without grease.

al
 
alinwa said:
First of all, understand that I am one of the people referred to as "overthinking this stuff."

There are some things I will disagree with in the above statements.

#1, minimum dimension chambers WILL NOT help to contain your primer pockets. I've got chambers that run the gamut from tight to loose in 5 common chamberings and can state from actual testing that you CANNOT contain caseheads using either the chamber or the boltface recess.

#2, fireforming using sloppy end clearance WILL result in crooked brass. This is specifically why some folks will always advocate greasing cases. Itr's the ONLY reason for greasing cases.

Many folks disregard the fact that we Stand on the Shoulders of Giants, that pioneers have gone before us and paved the way, that a lot of what we do has been bought and paid for by others.

"Overthink" my achin' ass........ accuracy is hard. What makes me laff is when the "doers" come back after several years and preach what they scoffed at prior. I see this a lot.

go out, spend the money and find out for yourself.

Or lissen to the thinkers.

BTW, where did you find SAAMI specs for the PPC?

al
Click to expand...

I don`t know if you`re interested, but CIP backs the 6mm PPC. I`ve never seen a SAAMI drawing.
the CIP drawing for cartridge and chamber is on pg70 of this site.
http://www.poliisi.fi/intermin/images.nsf/files/AE55118F4B9B6506C2256FBE0032C6DE/$file/TABIcal.pdf
 
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