My son has two of them. The story is that the older USA made CVA Mountain Rifle barrels were made by Douglas.
That's what I understand as well, and my rifle barrel is stamped; Made In USA, and it also carries a maple stock.
I also have other Douglas barrels and the one thing I've learned in using them, both in .45, and .50 caliber, they like a tight patch and ball combination. This has been my experience.
As for 70 grains of Pyrodex,,, it is my understanding that this is the equivelent to 90 grains of black powder. That equates to about 470 ft. lbs. at 100 yards. That should
be adequate for elk in that range and under. If you feel you need to get up to 500 ft. lbs. at 100 yards, try 80 grains of the Pyrodex with this equaling 100 grains of black powder and 500 and change ft. lbs of energy at 100 yards.
Just some suggestions. Right now by using 90 grains of Pyrodex you're producing about 540 ft. lbs at 100 yards. That's about 110 grains of black powder.
Which ever you decide, I still think much is going to rely on a good tight fitting patch and ball combo in that Douglas barrel. You can always reload with a looser fitting combo after your shot, but personally I'd stay with the tight combo and spend the few extra seconds it takes to load it.
Good luck!