Speaking of 50's...the Govt Round

[Kurt]

I personally would not go with a groove deeper then .004" I just went through that with a barrel that had a .00575" deep and it shot great verticals of as much as 15" at 200 yards. A PP bullet will just not fill the grooves enough to hold the gases back to hold an ES. A GG bullet would cast at groove depth but you would never be able to seat it out deep in the bore.
The fouling collection in the bore with that deep groove was a bear. I have seen more original rifles with grooves very shallow then the .004" now used and they worked just fine.

Kurt