Don,
I have used all different type greases and any good quality HIGH PRESSURE grease will work! But, I receommend the that you give the syhnthetic lubricants a try. Neil Keller has graciously offered to send you a sample and I do recommend his grease. The KELLUBE is fantastic! It is high pressure, does not attract dirt as bad as regular grease, and will not let the stainless "gale" with itself. Only a small amount is needed to wrok effectivly. You will love the synthetic grease better than any other you have tried.
For years, I use a synthetic grease on my M-14 Nat. Match rifle and never had any problems. Oh yea, it is far more heat resistant too.
Marvin
P.38 Forum