The point of using Trail Boss is to get light velocity with high case fill.

Cyrano,
If you want to get more out of the 45Colt and your Mountain Gun, look in the "Ruger/TC" only section of the newest Lee manual. There are some real whompers there and I think I would leave the heaviest of those alone, but there are loads that are what I would call +P ones that would be fine in your firearm. Look for data that doesn't exceed 20,000psi. There may even be some loads with W231/HP-38 there as well.

The M625 will take 20,000psi all day long and stay tight. There are folks that regularly load them to 30,000psi. You will find some of those loads in that manual too, I wouldn't start off with them though!