Cartridges Gaining Butt Girth with Age?

[INTJ]

Maybe it is just the natural order of all things to grow in girth on the bottom end. People, trees, dogs......but I didn't think it would ever apply to cartridge cases.

In 2005 I had my first 1000 yd BR rifle built in 300 WSM. I ordered a match reamer from Dave Kiff and let him pick the specs. That first rifle was a LG and it shot very well, shooting screamer groups, winning aggs, and even setting a couple of club records from 2005-2007. I used Rem brass, Redding dies, and everything worked well.

I came back to LR BR in 2018 and got a lathe and a mill. In early 2020 I decided to try a 300 WSM LG again. I used that same reamer. Several on this forum told me that my reamer was too tight at the .200 line. I had custom dies made. I used Norma brass and while the rifle wasn't great at 600 yds, though I did win for score, I had no issues with brass at all. I decided to go back to 6 BRA for LG and build a 300 WSM HG.

Last week I got the HG finished. I went out and shot it with the Norma brass I had used in my LG. Even though it was the same reamer chambered by the same guy (me), the HG chamber is tighter than the LG chamber. The LG brass would size down and the bolt closed with no resistance, but when fired bolt lift was heavy.

This wasn't a pressure issue. The soft Fed 210s still had round edges, there were no extractor marks, and the velocity wasn't high. Once brass expands in the head, it never forgets and it likes to go back to that larger size when it's fired, even if it's sized down first. I knew this going in but hoped it would be close enough.

Well, I resigned myself to prepping new brass. I had 200 Nosler cases and started with those. However, the bolt wouldn't close without a lot of effort on this new brass even when sized. So I measured the head. Both the Nosler and Norma were .552 at the head. My reamer is .5527 at the .200 line, and I made this HG chamber right.

Then I remembered that I still had 150 rounds of the original Rem brass I used in 2005-2007. I checked those cases and they measured .548 at the head, .004" less. So I prepped all those cases and am heading to the range to test.

I have no idea why WSM brass has grown in the butt over the years. Regardless, I do have 190 300 WSM Nosler cases that all weigh within 1 grain of each other to sell....

 

[457ciSBC]

My 2 cents......over the years we have see various cartridges that have grown a few thousands larger at the .200 point. The public wants a case that’s more robust (higher pressure tolerate) in the primer pocket area and that comes with a price, the extra mass has to go somewhere.

 

[Rsadams]

I honestly don't think this is so odd...If I am reading this correctly which can be alot to ask sometimes.... Your thinking that a different barrel should be the same as the first even though you're using the same reamer that doesn't mean the barrels are the same in hardness etc or even that when you were cutting it you left it in the chamber as long etc... Everything is different especially giving the time difference.... I could be absolutely wrong but it doesn't seem like anything is necessarily wrong... I am sure someone else who has alot more experience than myself will chime in.... I am interested in your post so I will check back and see...

 

[INTJ]

I honestly don't think this is so odd...If I am reading this correctly which can be alot to ask sometimes.... Your thinking that a different barrel should be the same as the first even though you're using the same reamer that doesn't mean the barrels are the same in hardness etc or even that when you were cutting it you left it in the chamber as long etc... Everything is different especially giving the time difference.... I could be absolutely wrong but it doesn't seem like anything is necessarily wrong... I am sure someone else who has alot more experience than myself will chime in.... I am interested in your post so I will check back and see...

No sweat, I took a long to just to say that I am amazed that brass from 2005 measures .548 at the head while today's brass measures .552.

I am sure Dave Kiff knew that so it made sense for him to make a tighter reamer in 2005 than he does today. I'll just have to get a new reamer when I am done with this barrel.

 

[Rsadams]

No sweat, I took a long to just to say that I am amazed that brass from 2005 measures .548 at the head while today's brass measures .552.

I am sure Dave Kiff knew that so it made sense for him to make a tighter reamer in 2005 than he does today. I'll just have to get a new reamer when I am done with this barrel.

I see what you're saying now sorry.... I was about to sweat to death when I read your OP... That is crazy how things change over that amount of time... I was nail sweeping my yard after having a new roof installed , for the fourth time.... Just did it again now that it's almost dark instead of 3:00 in the afternoon in central Texas... Start again tomorrow...

 

[JASmith]

I see what you're saying now sorry.... I was about to sweat to death when I read your OP... That is crazy how things change over that amount of time... I was nail sweeping my yard after having a new roof installed , for the fourth time.... Just did it again now that it's almost dark instead of 3:00 in the afternoon in central Texas... Start again tomorrow...

0.004” growth in diameter of new brass seems to be a lot. It would be interesting to compare the new case diameter at 0.200” with the current SAAMI specs.

 

[Uthink Uknow]

Cases simply grow in girth at the .200 datum line and that is a fact of life. You may try different shell holders to size tighter at the base but then you bump the shoulder too far back. We build and sell “ring dies” to size the base of the case only and have them in what would be standard sizes for WSM sized cartridges in .5545, .5535 and .5460 and .5495. We have these sizes in stock now. The die is straight I.D. Reamed and hones to exact specs. And diamond honed on the lower radius. Here is a picture of one such die and one of my .30BR cases with 50 firings on it. I size my cases after every firing and follow that up with a run through the ring die as well after every 3rd or 4th firing. we sell a die for $135.00 plus shipping and that sure beats making new brass or fighting with tight brass.
We can also make a custom die to any diameter you like at no additional cost.

 

[philip brousseau]

Tag

 

[JMayo]

Cases simply grow in girth at the .200 datum line and that is a fact of life. You may try different shell holders to size tighter at the base but then you bump the shoulder too far back. We build and sell “ring dies” to size the base of the case only and have them in what would be standard sizes for WSM sized cartridges in .5545, .5535 and .5460 and .5495. We have these sizes in stock now. The die is straight I.D. Reamed and hones to exact specs. And diamond honed on the lower radius. Here is a picture of one such die and one of my .30BR cases with 50 firings on it. I size my cases after every firing and follow that up with a run through the ring die as well after every 3rd or 4th firing. we sell a die for $135.00 plus shipping and that sure beats making new brass or fighting with tight brass.
We can also make a custom die to any diameter you like at no additional cost.

I'm interested ....Where to buy ?

 

[INTJ]

Cases simply grow in girth at the .200 datum line and that is a fact of life. You may try different shell holders to size tighter at the base but then you bump the shoulder too far back. We build and sell “ring dies” to size the base of the case only and have them in what would be standard sizes for WSM sized cartridges in .5545, .5535 and .5460 and .5495. We have these sizes in stock now. The die is straight I.D. Reamed and hones to exact specs. And diamond honed on the lower radius. Here is a picture of one such die and one of my .30BR cases with 50 firings on it. I size my cases after every firing and follow that up with a run through the ring die as well after every 3rd or 4th firing. we sell a die for $135.00 plus shipping and that sure beats making new brass or fighting with tight brass.
We can also make a custom die to any diameter you like at no additional cost.

I think you are referring to cases growing at the .200 line after firing, which is indeed a common issue and yes, a ring die--which I have--is the solution in most situations and I am glad to see that you have them in stock.

The only time a ring die doesn't always work is when a case has been fired in a larger chamber, sized, then fired in a smaller chamber. Even when sized with a ring die to the correct diameter for the smaller chamber, the brass often remembers and will try to expand all the back to its original larger size, making bolt lift heavy.

However, I am talking about unfired brass specs and how 2005 vintage Rem brass is .004" smaller than new Norma and Nosler brass. That is a lot more variance than I expected. It also means that as a newbie hobby gunsmith, that I need to spec out the brass I want to use before using an old reamer.

What I am wondering is if a ring die was used on new, unfired brass, would the cases work in a chamber that is tighter than the original unfired size of the brass?

 

[JMayo]

Cases simply grow in girth at the .200 datum line and that is a fact of life. You may try different shell holders to size tighter at the base but then you bump the shoulder too far back. We build and sell “ring dies” to size the base of the case only and have them in what would be standard sizes for WSM sized cartridges in .5545, .5535 and .5460 and .5495. We have these sizes in stock now. The die is straight I.D. Reamed and hones to exact specs. And diamond honed on the lower radius. Here is a picture of one such die and one of my .30BR cases with 50 firings on it. I size my cases after every firing and follow that up with a run through the ring die as well after every 3rd or 4th firing. we sell a die for $135.00 plus shipping and that sure beats making new brass or fighting with tight brass.
We can also make a custom die to any diameter you like at no additional cost.

Thought I'd bring this back to life with pics.
6bra 20+ firings after using the die.

The annealing ring down was resized on several. At the .200 line on others.
If I can get a season outta these it will have paid for itself.

 

[mikecr]

Both the Nosler and Norma were .552 at the head. My reamer is .5527 at the .200 line, and I made this HG chamber right.

What does the fired brass measure at that datum?

 

[INTJ]

What does the fired brass measure at that datum?

I found someone local with a lathe and he let me polish my chamber. I was told by a gunsmith/LRBR champion/friend to use 220 grit until the fired case would go in the chamber easily, then polish with 400 grit. I may have overdone it a bit, think I enlarged it .002 when .001 would have been enough. My Norma brass now fits and I think the Nosler would work as well.

Brass fired in the polished chamber now measures .5525 at the 200 line. It was .5505 at the 200 line before. That seems like a lot to have polished off, but I no longer have clickers.

All this also put my load out of tune, but I think just a little more powder should fix that. I am testing that tomorrow. Before the polish I was getting .6 to .7" 5-shot groups at 300 yds. After polish it went to 1.19". I really need to be under 3/4" at 300 for this load to compete well at 1000.

 

[mikecr]

You said earlier: "Both the Nosler and Norma were .552 at the head. My reamer is .5527 at the .200 line"
With this: "Brass fired in the polished chamber now measures .5525 at the 200 line. It was .5505 at the 200 line before" doesn't make sense.

 

[INTJ]

You said earlier: "Both the Nosler and Norma were .552 at the head. My reamer is .5527 at the .200 line"
With this: "Brass fired in the polished chamber now measures .5525 at the 200 line. It was .5505 at the 200 line before" doesn't make sense.

I have discovered more and there is now too much to this now to explain here...........

Although the Rem brass was .5475 at the 200 line when unfired.

 

[INTJ]

The back about 0.200" or a little bit more is not in the chamber. It sticks out so the extractor can grab it. So there is no chamber to limit expansion.

Actually, that part is indeed well within in the chamber. The case head is completely supported. Here is a barrel I chambered for one of my BAT actions

 

[Webster]

Actually, that part is indeed well within in the chamber. The case head is completely supported. Here is a barrel I chambered for one of my BAT actions

View attachment 1259819

Looks like I was wrong. I thought I saw drawings that showed more sticking out of the chamber. Look at post #11 why is there a shiny area at about 0.200". I see this a lot. Why do we measure for signs of pressure with a micrometer at 0.200". Is it just a place that's easy to locate on a case? Is 0.200" where most case body seperation occur? Just trying to learn more. Been reloading since 1970 and have never had a problem.

 

[Homerange]

Looks like I was wrong. I thought I saw drawings that showed more sticking out of the chamber. Look at post #11 why is there a shiny area at about 0.200". I see this a lot. Why do we measure for signs of pressure with a micrometer at 0.200". Is it just a place that's easy to locate on a case? Is 0.200" where most case body seperation occur? Just trying to learn more. Been reloading since 1970 and have never had a problem.

It's the point above the thicker base of the case where the wall thickness has thinned to become more parallel so shows any bulging earliest. Split a case with a hacksaw and you'll see what I mean.