7mm PRECISION RIFLE CARTRIDGE

[Lithgow]

"Load From A Disk" spec sheet for the 300 RCM tells me that the engine room/powder chamber wall is 0.0225 at the Web and 0.0112 at the Shoulder. Thicknesses for the 7 SAUM are 0.0404 and 0.0202. Based on that information, the capacity of the powder chamber of the 6.5 PRC is larger than that of the 7 SAUM by more than 5%.

Shobby, John, Frank and anyone who has loaded the 6.5 PRC and the 7 SAUM, what do you say?

IF LFAD and my calculations are correct, Shobby, you and your gunny could make a very nice 7mm, with at least 3% more powder chamber capacity than the SAUM and with a 0.315 neck.

Regards,
John T.
9.1.23

The 20thou of larger body at the shoulder of the SAUM is where its greater case capacity comes from but actual capacity between the two is very close, closer than most would think....

[Shobby]

Hi John T
I have shot both for some time 6.5prc (2 years) 7mm SAum (12years). The 7mm SAUM has definitely got the larger capacity but not by much. Initial testing 2 years ago showed me about 4% larger capacity than the 6.5prc but the ballistics that can be achieved more than makes up for it by running the heavy high BC 6.5mm projectiles against running the Berger 180gn Hybrids. They are virtually identical. (proven and tested through the target). I can give those numbers which have been proven through the target at 1000yds.
The necked up 6.5prc would make a good 7mm given 8gns less powder not taking into account the different in the density between the two powders. I'm running my 6.5prc on 2225 and the 7mmSAUM 2217.