Pressure rating of Different Calibers
- Thread starter ZeroJunk
- Start date
arizona hunter
New member
You may wish to check out the SAAMI web site for info.
Although sometimes it does appear arbitrary, mostly it looks like they are just being cautious due to very old designs (like my 6.5 x 55 Swede is a 96 Mauser vs. a 98 or newer). Also it appears that there are different specs when a cartridge began as a wildcat due to the many different chambers made by the wildcaters before the cartridge was picked up by one of the big factories.
Although sometimes it does appear arbitrary, mostly it looks like they are just being cautious due to very old designs (like my 6.5 x 55 Swede is a 96 Mauser vs. a 98 or newer). Also it appears that there are different specs when a cartridge began as a wildcat due to the many different chambers made by the wildcaters before the cartridge was picked up by one of the big factories.
A lot of variables enter into the equation. What kind of rifles is the cartridge chambered in, how much freebore does it have, what is the relation between case diameter and bore size, as well as how much body taper does the round have are all factors. The SAAMI site has a lot of info on it.
It has to do with when the round was adopted. Certian rounds can see an improvement in modern guns (45-70 for example) I see the max pressures as the redline of the round, once you go past that point, you are on your own. I only hotrod two rounds, the 22-250 and the 45 Colt. Other rifles that have weaker actions I stay well below the max data and generaly stick with the starting loads.
Where??? I spent ten minutes searching http://www.saami.org/ for info about common caliber pressures and testing info. Came up with zip zilch nada.
Looks like my massive archive of gun related internet links has come in handy.
SAAMI Pressure Specs
/Has a copy of SAAMI specs on gun safe.
SAAMI Pressure Specs
/Has a copy of SAAMI specs on gun safe.
Edward429451
Moderator
So why is it that 30/30 and 444 Marlin are both listed at 42K and 45/70 is at 28K. All are LA rifles. Can I exceed 28K in my 45/70 GG with no fear of damage to the gun? I do not own any trapdoor springfields so ammo mixup would not be a problem.
Ruger #1 loads appear to top out at 40K in the manuals, so it's not the brass.
Someone 'splain.
Ruger #1 loads appear to top out at 40K in the manuals, so it's not the brass.
Someone 'splain.
The 45-70 has such a low pressure spec because of the trapdoor rifles. Almost all factory ammo is loaded so it won't blow up a trapdoor. In reloading manuals there are 3 levels of 45-70 loads: Trapdoor, Modern Lever action, and Ruger Only. Loading the Lever Action loads will result in a big performance boost. I'll have to take a look at my Speer reloading manual to find the pressures of the Lever and Ruger load data.
Jim Watson
New member
High end published .45-70 loads - the 28,000 stuff - is for the stronger old line guns like 1886 Winchester.
No doubt your Marlin could stand more but in addition to chamber pressure, you have to consider case head area and bolt thrust. The .45-70 is a big diameter case so its pressure has a lot of area to act on, and that is what your rifle's lockup sees.
The question now becomes, not whether you can safely exceed 28,000 psi by some amount, but to know what that amount is and when you have reached it. I know of no finely graduated load tables from, say 30,000 to 40,000 psi in 2000 increments. So you would be thrown back on computer programs and rules of thumb. I think the high end regular loads are plenty for my use.
No doubt your Marlin could stand more but in addition to chamber pressure, you have to consider case head area and bolt thrust. The .45-70 is a big diameter case so its pressure has a lot of area to act on, and that is what your rifle's lockup sees.
The question now becomes, not whether you can safely exceed 28,000 psi by some amount, but to know what that amount is and when you have reached it. I know of no finely graduated load tables from, say 30,000 to 40,000 psi in 2000 increments. So you would be thrown back on computer programs and rules of thumb. I think the high end regular loads are plenty for my use.
Edward429451
Moderator
Good answer and just what I wanted to hear. Top end 28K loads are enough for me too.
I ran some 350 gr bullets loaded to 1613 fps & 1886 fps through the ballistic explorer (21K & 39K respectivly ala quick load) and there's so little difference in the flight path & MPBR that I see no reason to use the 39K load. Why increase the wear on the brass, gun and shoulder when there's no practical benefit? Thanks.
I ran some 350 gr bullets loaded to 1613 fps & 1886 fps through the ballistic explorer (21K & 39K respectivly ala quick load) and there's so little difference in the flight path & MPBR that I see no reason to use the 39K load. Why increase the wear on the brass, gun and shoulder when there's no practical benefit? Thanks.