You may be aware of this, but Roy Dunlap used to market an alteration to the Model 70 bolt shroud which incorporated a flange on the left side, the purpose of which was to block the bolt raceway from escaping gas caused by a pierced primer or other mishap. You might be able to include that feature in your mounting base.
One of the most obvious faults with the Model 70 design was its poor ability to handle escaping gas.
I think I have a photo of the Dunlap alteration somewhere in my files. If I can find it, I will post it here.
