Fast twist = more pressure?

[WeiserBucks]

It just seems odd that many others are loading 84-85 grains of H1000 , 230s and getting close to 3000 FPS in a 26" . These same shooters are also claiming 5-7 firings on Norma brass.

The 1st load I tried was 83 grains of H1000 and 225s, it made 2960 and killed the brass in one firing.

 

[tim_w]

I'll do you one better, I just received 250 pieces of Peterson brass

I think their brass ran a bit tight in the head area so don't be surprised if you get a bit of swell depending on your chamber spec. I know someone posted on this when the Peterson NM cases came out. It should be within the first few pages in this or the rifle ballistics forum.

 

[tim_w]

It just seems odd that many others are loading 84-85 grains of H1000 , 230s and getting close to 3000 FPS in a 26" . These same shooters are also claiming 5-7 firings on Norma brass.

The 1st load I tried was 83 grains of H1000 and 225s, it made 2960 and killed the brass in one firing.

Was it primer loosening and/or case head expansion as well? Might also want to check the h2o volume of your cases and compare to that of others. I know norma has had variations in the past in case volume.


With your load you should not have wrecked the case in one loading. That takes over 70k normally. Can you accurately find and mic the largest diameter section of those eld bullets and see what you get.

 

[J E Custom]

With every brand of brass being different, and every chamber being slightly different, my first thought would be the dies are not seating the bullets deep enough to allow bullet jump.

Also different cases have different case volumes. (Smaller volumes can increase the pressure with the same load.

With the big Magnums. some freebore/bullet jump is necessary to reach high velocity @ SAMMI pressures. Check your bullet jump to see what it is and then try seating .010 to .020 deeper.

J E CUSTOM

 

[WeiserBucks]

I've been running them at .020 off the lands

 

[gohring3006]

Did it always show pressure?
Or did start after some rounds thru it?
Standard reamer, or???
Reason I ask is,
Is there a carbon ring already, this happens sometimes with in just. 20-30 rounds with some powders and chambers.
The reamer can affect pressure depending on throat and freebore.
I had a 7 mag that gave me pressure at light loads, I started using hex, and it smoothed out the pressure curve and allowed me to get the velocity I wanted.

 

[WeiserBucks]

The very first round I fired with 83 grains of H1000 ruined a piece of the Norma brass. Backed it off to 81 grains and zero pressure signs.

 

[Nieko]

WeiserBucks, I have been fighting the same thing with my 300 Norma. 24 inch 10 twist Benchmark- 81 grains of h1000 with 230 berger. Virgin Norma brass chambers smooth and ejects fine, second firing starts to get stiff(had to have Whidden make me a die to get base area sized down enough to chamber). The brass is too soft and not enough spring back. It grows substantially each firing and creates a donut inside the case at the neck shoulder junction. If you don't ream the donut out, you will see pressure rise.(could be your problem) I would say it is not your 8 twist causing pressure. I just got some Peterson brass and I will begin to run it through the paces to see if it is not as soft as Norma as far as growth goes.

 

[WeiserBucks]

Peterson brass is looking promising, 85 grains of Retumbo and 230s produced 2969 fps. Brass showed just the slightest signs of pressure and grew .002 at the case head . ES was pretty wild , I'm going to load a few with H1000 as it was producing single digit ES with the Norma brass.

 

[Pdvdh]

If the case head diameter grew 0.002" on the initial firing, your pressure is excessive, in my experiences.

 

[WeiserBucks]

I would tend to agree , however I've been testing different loads all day with interesting results. I've tried 2 different powders and 3 different bullets.

I've loaded the 230s from 2700-2969 , all grew .002". Loaded 215s from 2850-3060 , all grew .002" .

 

[Pdvdh]

I'll suggest loading one casing repeatedly at those pressures to see how many shots your primer pockets hold snug. Will help ensure case life is acceptable to you at those pressures

 

[WeiserBucks]

I'm running a durability test as we speak. So far after 3 firings of 87 grains of Retumbo and 215s the case head hasn't grown past the initial .002" , length grew .007" after 3 full length sizings and needed to be trimmed . Primer pockets are still like new . I'll report back later once it's a confirmed kill .

 

[WeiserBucks]

I pussed out at 10 firings, got tired of swapping dies ect . Primer pockets are still like new, had to trim 3x . After 10 firings, no case head expansion beyond the initial .002" on the 1st firing.

Peterson brass is for real folks.