Home Forums Reloading Varmint Rifles Why are different max pressures allowed in similar cartridges?

Why a different pressure allowance for the .222, the .223, or the .204 Ruger? It would seem not to be totally because the .222 was available in some less strong actions. Is there any reason that a .222 Rem in a Rem 722, a Cooper, or a Sako can't be run at the pressure levels of the .204 Ruger?
Is increased bolt thrust the reason that .308 bolt size cartridges, like the .270, tend to be allowed higher pressures?

Some older cartridges were developed prior to transducer technology to measure pressure, and haven't really been updated. Some cartridges are limited by the actions they may be found in, or their brass. Some cartridges exhibit odd pressure variations at times during a string of pressure testing which causes them to have a lower listed pressure to account for it.

In a modern rifle, with modern brass, I cant see a reason not to push the 222Rem a bit harder, and many do. Next question becomes, as you reach beyond published limits, how will you know whether your loads are 63k psi loadings, or 70k psi loadings when many of the signs associated with high pressures on the case often appear at much higher pressures than what a factory would allow?
Cheers...
Con

I use Quickload to get an idea of pressure using my true case capacity. Then I use velocity to help get a good idea of where I am. (If any pressure signs are evidenced, I back off quite a bit and at once, but seldom see any.) As for velocity, if a max at 55,000 psi for the fireball gives about 34-3500 for 40 grainers, and another 200 fps for the .222 Mag, than I figure that the .222 ought to give 35-3600 at comparable pressures. Seems to work OK.

Burning rates are effected by the cases fired in. So while a "good" indicator of pressure, velocity isn't the end-all. If you want to know what pressures you are truly running in your set-up, buy a Pressure Trace system.

What this guy said. It works. No more guessing.

I am inclined to believe that pressure levels were targeted more to the rifle than the cartridges. Prior to WWII, and after, a lot of experimentation was done. An example would be the Winchester model 43 was chambered for the 22 hornet, 218 Bee and I believe the 32-20. Actions were soft and frequently developed headspace problems. Many actions were brought back from the war, some questionable as to their strength.

If you review the old loading manuals, the 257 Roberts showed a maximum load far under modern american made gun loads. Right or wrong, powder or bullet companies wanted to protect themselves, thus published lower pressures on some cartridges.

At the time I had a 257 Roberts that would take 5 grains more H4831 before showing pressure signs, than any of the loading manuals.