After having a positive experience with 7MM/08 Lapua brass, I purchased some in .243. I had serious pressure problems using the exact same load that had worked quite nicely in Winchester brass. The bolt handle had to be firmly rapped in order to get the Lapua brass ejected. After reducing the powder load several times, I finally got a very light load that would eject and showed no signs of pressure. The other day I weighed a sampling of both the Lapua and Winchester brass. On average the Lapua weighed 15 gr. More than the Winchester. My question is: could this difference in case capacity be enough to cause my pressure difficulty? One other sidebar, I had to uniform all the Lapua primer pockets in order to get my CCI primers to seat in the initial seating. I’d appreciate your thoughts.
Case capacity question.
- Thread starter Topwater
- Start date
I had similar problem with Lapua 308win brass...
I worked up a load and once I saw signs of pressure I backed off 1 gr. at a node.
After 3 reloads I was getting pressure signs, so I backed off 2 gr down to the next node.
All was ok for 2 more reloads, then pressure signs showed up again and no matter what I did the brass would not shoot anymore.
Also could never get 243win and 7mm08 Lapua brass to shoot as good as Winchester brass.
I worked up a load and once I saw signs of pressure I backed off 1 gr. at a node.
After 3 reloads I was getting pressure signs, so I backed off 2 gr down to the next node.
All was ok for 2 more reloads, then pressure signs showed up again and no matter what I did the brass would not shoot anymore.
Also could never get 243win and 7mm08 Lapua brass to shoot as good as Winchester brass.
The 243 and 7mm-08 appear to be the same as Winchester’s 308 brass (157 - 160gr). I forget the term but Winchester removed some material from the case head to increase capacity for some Palma match brass in the 90’s if I remember correctly and stayed with it for commercial brass. It typically works out to about 2gr of water more than LC brass and about ~1.3gr for Lapua.
In 308 I typically back off .3 grains for Lapua brass but this is not on a high node.
In 308 I typically back off .3 grains for Lapua brass but this is not on a high node.
Case capacity can have a major difference. I retired some .308 Hornady cases I was working up a load with and bought 100 new cases. I was using 200.20x Berger bullets and powder charges were within .02g and all set to jump .005". My group size suddenly got quite a bit larger. The average velocity before was 2,531 fps and with the loads exactly the same and the weather conditions similar, the average dropped to 2,495. I started working up the charge. I had to go up from 42.5g to 43.2g of Varget to get the velocity back and the accuracy returned with it. I spot checked several cases and they new lot averaged about 7% larger in capacity.
When considering that Winchester brass has thinner walls than Lapua, this stand to reason as Winchester brass will have less brass material than Lapua given the same outside dimensions.
To put it simply . . . YES.
Ned Ludd
Silver $$ Contributor
You're lucky you didn't kill the primer pockets of every piece of Lapua brass in which you ran your Winchester brass load. Any time you change a component...ANY component, it must be treated as a new load development. That is, you start at the low end and work up carefully and incrementally.
Bullets from different Lots don't always have the same dimensions, powder from different Lots may not have the same burn rate, and primers from different Lots may exhibit different brisance. Different brands of brass can have widely different case wall thickness and therefore widely different internal volume. Even Lot-to-Lot variance in case volume can be observed with same brand of brass.
Bullets from different Lots don't always have the same dimensions, powder from different Lots may not have the same burn rate, and primers from different Lots may exhibit different brisance. Different brands of brass can have widely different case wall thickness and therefore widely different internal volume. Even Lot-to-Lot variance in case volume can be observed with same brand of brass.
Winchester308 for a long time was the go-to brass among Palma shooters.
Pushing <156 grain 308 bullets to stay supersonic benefitted from the copious case capacity Winchester provided. (Keep in mind too this was when Sierra’s 2155 / 155 SMK was about the only 155 grain bullet out there, affectionally referred to as an aerodynamic brick....)
Newer bullet designs are more efficient (though 2155’s are still used by some) so case brands with less capacity are more the norm (to say nothing about how Winchester brass QC has been vilified since they abandoned production at the East Alton ILL plant years ago) despite their higher cost.
The only 308 case I know that has less capacity than Lapua’s two offerings (LR & SR primer styles, the latter tagged as Palma brass) is pretty much any year’s LC-stamped 7.62 NATO stuff. But it’s real close.
Developing a load using Win cases, then switching to another brand of case without backing off charge weights is a known-easy way to ruin new brass at the first firing.
Pushing <156 grain 308 bullets to stay supersonic benefitted from the copious case capacity Winchester provided. (Keep in mind too this was when Sierra’s 2155 / 155 SMK was about the only 155 grain bullet out there, affectionally referred to as an aerodynamic brick....)
Newer bullet designs are more efficient (though 2155’s are still used by some) so case brands with less capacity are more the norm (to say nothing about how Winchester brass QC has been vilified since they abandoned production at the East Alton ILL plant years ago) despite their higher cost.
The only 308 case I know that has less capacity than Lapua’s two offerings (LR & SR primer styles, the latter tagged as Palma brass) is pretty much any year’s LC-stamped 7.62 NATO stuff. But it’s real close.
Developing a load using Win cases, then switching to another brand of case without backing off charge weights is a known-easy way to ruin new brass at the first firing.
The Speer reloading manual, think it's the latest edition but maybe not, comments specifically on this issue in its 243 Win technical notes saying the loads data-sets were developed and pressure tested in Winchester brass and stresses they mustn't be used with other case makes. It says that in their technicians' experience, 243 had an unusually large variance in capacities, more than enough to cause over-pressures.
As Ned Ludd says, switching components (especially brass) in nay cartridge really does need a charge reduction and load rework, but the fact that Speer singled out 243 Win for this comment is interesting and likely significant.
As Ned Ludd says, switching components (especially brass) in nay cartridge really does need a charge reduction and load rework, but the fact that Speer singled out 243 Win for this comment is interesting and likely significant.
I was told long ago that eight to ten grains of extra case weight was equal to an extra grain of powder,it would be advisable to batch your cases and load to suit the case capacity.
1.5 grains less in heavy 22Nosgar cases compared to lighter 22Nosler cases works for me.
Case weights in the pic include a reversed fired primer.
The Nosgar (6mm Hagar) have been set back on the shelf for now.
I use Nosler brand 22N or Nosler Dogtown now. About a 3 grain difference.
I have measured water volume on both of these, New, and Fired.
I can hedge charges a tad and get pretty much the same external ballistics.
Try it. You'll like it.
Case weights in the pic include a reversed fired primer.
The Nosgar (6mm Hagar) have been set back on the shelf for now.
I use Nosler brand 22N or Nosler Dogtown now. About a 3 grain difference.
I have measured water volume on both of these, New, and Fired.
I can hedge charges a tad and get pretty much the same external ballistics.
Try it. You'll like it.
Last edited:
so, this is just proof positive that reading books before reloading is a good thing.
you change ANYTHING in a load, YOU BACK UP AND WORK UP AGAIN.
the simple safe thing here would have to measure case volume of each and make adjustments as required.
so now that you survived,
do it NOW.
AND THEN work up a load
you change ANYTHING in a load, YOU BACK UP AND WORK UP AGAIN.
the simple safe thing here would have to measure case volume of each and make adjustments as required.
so now that you survived,
do it NOW.
AND THEN work up a load
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.