OK, I think I follow. The guns we used would have been later as they were Canadianand we had a heavy bbl standard. I see the spot at the front of the bbl jacket you speak of without holes. The whole thing about the thin bbl is something we didn't issue, so that must have been early, this gun didn't surface until after WW2, right? Then would have succeeded to the...M60?
I guess this would be the time to acknowledge an apology to RCS for arguin'. I shoulda knowed better...