Gunsmithing 7mm SAUM gas gun question

I'm thinking of building one......anybody done a gas gun in 7 saum?.....or any magnum???

I'm wondering if it will be difficult getting it to feed reliably.
DPMS used to do a 300 saum or or something.

The guy at Accuracy Systems says he can do a gas gun in 7 WSM....but with the steeper shoulder on the wsm I question whether it would ever feed reliably.

I'm interested in hearing what other builders think.