Home Forums Hunting & Shooting Ask The Gunwriters Who Set Max Average Pressure For SAAMI Cartridges?

264 Win mag, 300 Win mag, 338 Win mag is set at 64,000 PSI, The 458 Win mag is 62,000 and the 7mm Rem mag is 61,000 PSI
Why would they not all be the same?

Winchester bribed saami so their cartridges could outrun Remington’s

Modern pressure testing results reveal the 7mm Rem exhibits a bit more irregularity shot to shot than originally thought. So the average pressure was lowered to reduce the probability of any particular shot exceeding the maximum allowable.

A similar change has occurred for the 243 Winchester.

I have wondered if it had something to do with the throating of the various cartridges. Never studied it to see if any correalation, but do know they are not all the same

Lou

Not arguing anything here, just wondering---specifically about the pressure limits of the .280 vs. the .270. I've read a lot of opinions stating that it had to do with the first rifles chambered in .280, but there seems to be some holes in that logic. Maybe there's more to it.

Yeah, that's a different situation.

Remington wanted a cartridge that approximated the 270 with low enough pressure to work in their semi auto

But they eventually chambered it in the 270 which moots the pressure consideration.

Not until they brought out the 7400, which involved some changes. They apparently never chambered the 742 in .270.

Exactly 💯

I read somewhere that Remington specified a lower pressure for the .35 Whelen so it could work in their semi-auto.
PJ

According to an old Gun trader's Guide with yellowing pages, the 742 was offered in 6mm Rem, .243 Win, .280, .30-06, and .308 Win. There is no reference to .270 Win in the 742.

MD, since the 6mm Rem is rated at 65,000 psi currently, but that long ago the copper crusher pressure measurements would have been used (I assume). Were the 6mm Rem C.U.P numbers the same as the .280 C.U.P rating when that system was in use?

I believe it was set by the original manufacturers in the case of new cartridges and the rifles they were chambered in. Old cartridges such as the 7x57 and many others were set to be safe in older rifles, such as the 93 Mauser, the Remington rolling block and so forth.

Answered my own question, remembered my old Lyman 46th manual lists pressures in c.u.p.

The .280 appears to have been limited to 50,000 c.u.p. and the 6mm Rem limited to 52,000 c.u.p.

So, if the .280 was set to 50,000 because of the action strength limitations of the 742, how is it that Remington saw fit to chamber the same rifle in 6mm Rem at 52,000 c.u.p.?

That's why I think there's some other reason. And maybe it WAS because Remington wanted the cartridge to operate at lower pressures from the outset, but the question remains, "why?"

quote=RiverRider]


Answered my own question, remembered my old Lyman 46th manual lists pressures in c.u.p.

The .280 appears to have been limited to 50,000 c.u.p. and the 6mm Rem limited to 52,000 c.u.p.

So, if the .280 was set to 50,000 because of the action strength limitations of the 742, how is it that Remington saw fit to chamber the same rifle in 6mm Rem at 52,000 c.u.p.?

That's why I think there's some other reason. And maybe it WAS because Remington wanted the cartridge to operate at lower pressures from the outset, but the question remains, "why?"[/quote]

The 6mm Remington is smaller in diameter and less bolt trust than the 280 would be my guess

The 280 was chambered in Remington's worst semi-auto the 740 (It's a POS rifle), which pre-dated the much better 742. The other chamberings were 244, 30-06 and the 308. I'm not sure why the 280 was loaded at lower pressure though.

Bolt thrust is determined by chamber pressure and the area of the case head. Both .280 and 6mm Rem are .473" diameter. The size of the bore has no bearing on bolt thrust. Assuming I'm not mis-remembering something...it's happened before!

Bugger, where did you dig that info on the 740 up?

Never mind that question.

The head gunsmith for Remington was a close personal friend. I’ve hunted deer and pronghorn with him and he used to come to visit. I worked at Illion in engineering and my brother was in upper engineering management at Illion.

The gunsmith friend told me the 740 wasn’t worth its weight in firewood.