Originally Posted By: dcrzfitter

The thought behind building on the mag upper receiver is to possibly be able to push this round a little more than with the standard AR15 upper.

As you dig into it, you will find that the upper receiver has nothing to do with containing the explosion.
That is the duty of the chamber, barrel extension and bolt.
Those three components are the "vault".

The upper receiver is just a "tunnel" for the BCG (bolt/carrier group) to ride in.

Olympic Arms has monkeyed with the WSSM cartridge in the mouse frame (AR15 as opposed to AR10) with varying degrees of success.
Many believe that their WSSM design renders critical areas too weak.

If you want a 458 SOCOM it is best to stay with Marty's design.
Just an oversized ejection port, 458 bolt and 458 barrel.
The round single stacks in a 5.56 mag.
No need to re-invent anything.

Welcome to BRD (Black Rifle Disease)....no known cure.
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NO STEP ON SNEK