Loosening Primer Pockets

[jpretle]

Seems to me, getting the most usable shooting life out of brass is the objective. At least that is my pursuit.
If you are running enough pressure to continue expanding the primer pockets, using a larger diameter primer will play out after another firing or two.
Measuring the head just above the extractor groove will let you know at what pressure the brass quits growing. Staying at or below that pressure level should give you the max amount of brass life, as the case mouth, neck, shoulder will give up before anything else---unless of course, you make annealing part of your brass prep.

 

[ShootDots]

Seems to me, getting the most usable shooting life out of brass is the objective. At least that is my pursuit.
If you are running enough pressure to continue expanding the primer pockets, using a larger diameter primer will play out after another firing or two.
Measuring the head just above the extractor groove will let you know at what pressure the brass quits growing. Staying at or below that pressure level should give you the max amount of brass life, as the case mouth, neck, shoulder will give up before anything else---unless of course, you make annealing part of your brass prep.

I JUST measured a few cases fired (0.499) and a few unfired (0.498)>> that is little or no pressure.. The measurements were taken at the base of the webbing right before the extractor groove..

 

[swampshooter]

I agree with measuring case head or web expansion just ahead of the extractor groove. I use this method when developing my loads and then back off the powder charge until I get "0" case head expansion. Maybe that's why I'm running a full grain less in my 284 than most others. I anneal regularly and I'm still using the same 100 rds. of brass that I bought when I first got my 6.5x284. I burned that barrel out and have about 650 rds. through my new barrel. I have about 15 loads with that brass now and still going strong, like the Energizer Bunny, it just keeps running. I've lost about three due to split necks.

 

[swampshooter]

If you don't want to be continually replacing your brass, I would consider .001 case head expansion as quite a bit. My guess is that you're opening up your primer pockets .0002 every time you fire, or thereabouts. Can you reduce your powder charge .5 grs. or even a full grain and still stay in a good accuracy node?

 

[swampshooter]

I'm shooting an unmodified 284 with 180 SMK's, jammed .005, 53 grs. of H-4831sc. My velocity is only running about 2800 fps, but accuracy is very good. Better than .4 moa. I figure at my age I'm not going to win any matches anyway, so that's good enough for me. I don't figure an extra 50 or 75 fps would gain me many points on the match anyway.

Bill Batson

 

[jpretle]

Shootdots, in order to get a baseline for case-head expansion you need to fire a new case in your chamber, using loads light enough for the brass to expand into your chamber. Once you have 2-3 cases you have done this w/, you have a starting point. You can then increase your powder charge---say in 1/2g increments until you get a notable jump in the head measurement. Having then reached this point, you have met the threshold of pressure for maximum case life. I generally back off 1/2g at a time here, until I get the accuracy I am looking for.
Bob Hagel has an excellent dissertation on this process, in his book 'Guns, Loads, and Hunting Tips.
I have been using this process for years, w/ excellent results.

 

[ShootDots]

My FireForming load is 55.5grs of H4831SC with 180 VLD's jammed 10k... In like butter, out like butter.. When I first got my Shehane, I was trying H1000>>>I found with that, and subsequent powders, that I have to be about 2885f.p.s. for my rifle to start shooting really good. I get "vertical stringing", "scatter groups", and least of all, E.S.'s that are 30 or so f.p.s.. I have no chouice, with this barrel but to be "up there" so to speak. Having said that, my "good loads" are still less than what Hodgdon states as max with a standard .284 using, I believe, a 175gr Partition. If you have ever seen one of those 175 Partitions, they have the longest bearing surface I have seen on any bullet, including the 180 Scenar "L"! Remember, a Shehane has right at 3.3grs more water capacity. So in reality I am no less that 3+grs UNDER max for a Shehane. I don't see where that could produce that level of pressure with a slow burning powder like H4831SC.. They go into the chamber like butter and come out like smooth butter and into my sizing die the same way... T-Rust me, there is NO INDICATION of pressure.. I am hoping, as others have iterated, that the "loosening" will eventually subside.. That, as we say, remains to be seen..

 

[ShootDots]

Shootdots, in order to get a baseline for case-head expansion you need to fire a new case in your chamber, using loads light enough for the brass to expand into your chamber. Once you have 2-3 cases you have done this w/, you have a starting point. You can then increase your powder charge---say in 1/2g increments until you get a notable jump in the head measurement. Having then reached this point, you have met the threshold of pressure for maximum case life. I generally back off 1/2g at a time here, until I get the accuracy I am looking for.
Bob Hagel has an excellent dissertation on this process, in his book 'Guns, Loads, and Hunting Tips.
I have been using this process for years, w/ excellent results.

I actually have that book in my library... Hagel was excellent! He was my fav author..

 

[bigedp51]

ShootDots

I'm not trying to change the topic but in AR15 forums over sized primer pockets and soft brass has been discussed quite often. Many of the problematic cases were traced to thin webs at the flash hole and this cause the primer pocket to expand. Below in the center of the photo is one of the cases with thin brass at the web flash hole and over sized primer pockets.

CatShooter was king enough to post the rockwell hardness of .223/5.56 cases and Lapua came in second behind military Lake City cases. BUT I'm wondering how thick the Lapua cases are at the web flash hole area?

To check for these cases a two inch rod was used to measure web thickness and the end of the rod inserted into the case was counter bored to clear any burs on the inside of the flash hole. And then the case was checked for web thickness and the defective thin cases were culled and gotten rid of. (or used for lower pressure loads)

Is it possible that the Lapua cases you are using are too thin in the base web area or does this happen with all your Lapua brass and is strictly a pressure issue.

You might need some cases built Ford Truck Tough.

 

[ShootDots]

It has been my experience with Lapua S/R primer brass, i.e. 6.5 x 47, is that it is nearly indestructible.. A few friends of mine use the Lapua "Palma" brass in their 308 F-T/R rifles and they are running "too high of pressure for "forum usage" and no discernible problems with their brass, including the primer pockets. I am beginning to suspect that, for whatever reason, the .284 case design (rebated rim) may have something to do with this as I never have this problem with other Lapua OR Norma brass without a rebated rim.. I don;t know.. BUT if there are any of you fellows that have the "wherewithal" to start a cartridge manufacturing company, making S-T-R-O-N-G 6.5 X 284 or a straight .284 case with thick webbing, to address these types of issues, would find a gold mine!

 

[swampshooter]

Hagel was my favorite gun writer also. I have an autographed copy of his book "Guns, Loads and Hunting Tips" in my library. His writings many years ago started me measuring cases to estimate pressures.

 

[ShootDots]

Hagel was my favorite gun writer also. I have an autographed copy of his book "Guns, Loads and Hunting Tips" in my library. His writings many years ago started me measuring cases to estimate pressures.

Bob Hagel was not only a "reloading hunter" if you will, he shot competitively, benchrest I think.. He employed many of those loading techniques to his hunting rounds. He loved those "Mashburn Magnums"! He was as far ahead of other hunters / loaders in his day as P.O. Ackley was in his niche!

 

[swampshooter]

I misspoke, CRS, I suppose. My Hagel book is "Game Loads and Practical Ballistics for the American Hunter" It's a first edition copyrighted 1978. I ordered it when it first came out. I was an avid reader of Hagel's when he wrote for the "Rifle" magazine.

 

[mysticplayer]

Nothing wrong with old Lapua brass.

So maybe it is in the action/chamber and bolt. If there is not enough support for the rear of the case, it will expand at moderate pressures.

Maybe there was extra space to account for the rebatted rim?

Maybe the base dimension of the reamer was a bit bigger then the case you are using so the case has to form to fit... and thus pockets loosen?

If this is correct, the brass will stabilize and "harden" to the chamber dimension...and thus, pocket size will no longer expand.

See if there is info on the reamer used or how your rifle is set up.

Jerry

 

[ShootDots]

I read Bob Hagel, Jack O'Connor, Layne Simpson, Jon R. Sundra, Dave Mileck and Rick Jamison almost exclusively. I loved to read about hunters who took great pains in reloading for their rifles..

 

[ShootDots]

Hey Mystic! I ordered the reamer from Dave Kiff.. I told him what I wanted, then he made a suggestion on neck and freebore, then I decided on a .315neck and .220freebore. Other than that, I don't have the reamer info anymore..

 

[swampshooter]

I have most of Jack O'Connor's books, I think all of his hunting oriented books, also Elmer Kieth, Karamojo Bell, James Corbett, Peter Capstick, J. A. Hunter, and a few others.

 

[ShootDots]

All excellent writers! You have a wealth of history as well as reloading knowledge at your fingertips!

 

[swampshooter]

Thank you, Ben. If I have any that you would like to read I would loan them to you.

Bill Batson

 

[ShootDots]

Thank You Bill! I may very well take you up on that offer!!