Fast twist = more pressure?

WeiserBucks

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Aug 16, 2016
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Been loading for my 8 twist 300 Norma. Anytime I even approach normal loads and velocity I'm seeing serious pressure, ruining the brass in 2 firings.

Could it be twist related ? I've been loading 225 ELD-M's over 81 grains of H1000 safely , getting 2900 fps initially, the same load is now clocking 2940 after 80 rounds fired .

Never used an 8 twist .30 before and I was expecting to load a little higher charge and get similar velocity to what many others are achieving.
 

MagnumManiac

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Feb 25, 2008
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I see that pressure/velocity is not effected by twist rate, BUT I do see a difference with the number of grooves and their width. My 3 groove match barrels in 300WM are faster than my 5R is at the same pressure.

I have a Remington and a Ruger in 25-06, the Ruger has skinny rifling, the Rem has the wide rifling. The groove number in each is the same which is 6.
The Ruger is faster than the Rem and shows pressure much later in the data, in fact it surpasses most loading manuals and the pressure trace shows the pressure is where it is supposed to be yet the velocity is higher.

Cheers.
 

Swamplord

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May 2, 2004
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H1000 may be the problem, you need a slower powder that allows up to 100% case fill before seeing pressure, I get that guys want to use H1000 due to it being more temp stable and availability but RL 33 is a much better powder for the 300 and 338 Norma Mags including the various improved cartridges
 

nbowlin

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Nov 29, 2011
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Imr 8133 is in the same park with retumbo, RL33 and 570. It takes a little more if it do the same speeds it seems. Which would help with case fill. It’s an enduron powder so it should treat you well with temp.
 

Mike 338

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Feb 4, 2012
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I had a 338 Norma in a Winchester 70 action that did the same thing. I had to load way down just to prevent pressure issues. I had one smith tell me it was an issue with the bolt. Sent the rifle in to another smith and he said everything was in spec. Never got a firm answer as to what the issue was. It makes me wonder if the brass was defective or to soft. Norma brass is notoriously soft. I ended up buying a new bolt/barrel and turning it into a 300 Win Mag.

Could be worth the effort of getting 10 cases of a different make and seeing if it helps.
 

WeiserBucks

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Aug 16, 2016
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Hopefully the Peterson brass will allow me to run the speeds I want with the powder I already have. I'm going to load a few this afternoon and see how they hold
 
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