Pressure

[Nova66et]

I've got a question about pressure. I looked up two loads:

308 load using a 165 gr bullet and IMR 4064 powder. It called for 42 gr starting load with 47,700 PSI, with a max load of 46.3c with 59,700 psi.

243 load using 85 gr bullet and IMR 4064. It called for 33.8 gr start with 49,200 PSI with a max load of 36 gr with a PSI of 56,700.

Question is, is the 308 built stronger to hold a high psi load than the 243 and if so is this normal variance across calibers

 

[45_auto]

SAAMI max average pressure for a .308 is 62,000 PSI.
SAAMI max average pressure for a .243 is 60,000 PSI.

http://www.saami.org/specifications_and_information/specifications/Velocity_Pressure_CfR.pdf

So yes, the .308 is designed for higher pressures.

The pressure range you're seeing across the loads from light to heavy is normal.

 

[rcmodel]

Both are based on the same case.
So the case is capable of handling the same pressures.

Most rifles chambered in both calibers are also capable of handling the same pressures.


But more variables can come into play blowing the same amount of powder through a small .243" hole then in a larger .308" hole.

Then again, SAAMI pressure limits make less sense then that in a lot of other calibers based on the same case.

So who knows?.

rc

 

[klausman]

The pressure rating may have more to do with the action it is fired in than the case per se.