My next long range build will be a 7mm short mag but I cant decide between 7WSM and 7SAUM. Is it True that you can equal the velocities but use less powder in the 7SAUM? If so then what advantage does the 7WSM offer?
I'm Trebark's buddy, guy looking for any favorite load data on the 7SAUM. Thanks to the folks that have replied. I appreciate it and I'm putting all this stuff in my notes.
On the 7WSM v 7SAUM issue. 7WSM appears faster by 50fps as it has a capacity advantage - however, there are a number of cartridge design issues with the 7WSM that reduce the actual speed advantage in the field.
(1) if you are building the rifle on a short-action, 7SAUM is a slightly shorter case, which is important because with the long 7mm bullets, you need every thousandths of an inch. Especially if you plan to mag feed
(2) 7SAUM has a longer neck, which puts the base of the bullet much less deep into the case vs 7WSM. Note that a lot of guys are necking down the 300WSM to 7mm for the longer neck in the 300WSM; however, the 7SAUM neck is longer than 300WSM.
(3) 7SAUM has longer, less sharp shoulders than the 7WSM. In theory, this should produce a more precise cartridge, although I'm not sure this plays out in real world (probably not apparent unless we put the guns on cement blocks); however, the shoulder on the 7SAUM do make it easier to feed the cartridge into the chamber vs 7WSM.
(4) barrel life. No other way around it: more powder thru the same diameter = less barrel life, so 7SAUM has an advantage there. I'm thinking 1500-2000 rounds for 7SAUM and perhaps 10% less for 7WSM. Some folks say longer necks reduce barrel wear; don't know if that is a fact or fiction.
(5) 7SAUM has some pretty good brass available- Nosler and Norma - although the Remington stuff is not up to par. Not entirely sure on the 7WSM brass.
There are a number of modified mags available to take the OAL length from 2.85-ish to 2.98-ish or even 3.10-ish and still mag feed on a short-action. 7SAUM appears to be the best cartridge for this route.
Best of luck on your build. And thanks again on the above load data.
