Does anybody use this product to protect the external parts of the gun, or do you use regular oil for that?
I use Bore Butter to protect the metal of my percussion arms, inside and out. I've got no complaints.
It does stiffen up in cold temps, and I do use it in sub-freezing conditions. I haven't experienced any undue grief in doing so.
I use it as a patch lube in both of my rifles. I use it on over-powder wads in my percussion revolvers and my percussion shotgun. After cleaning, I use it to protect the bores of my gun and rifles, as well as the chambers of my revolvers. I then apply the stuff on all of the external metal.
The newest percussion arm I own is 17 years old. None of them have a speck of rust on them anywhere. They get handled and shot frequently throughout the year.
However, one of my rifles (A Purdey replica made by Antonio Zoli and market by Garrett Arms) has been in storage for about 15 years due to problems with the lock that developed when I last shot it. It got cleaned up and got the Bore Butter treatment. Then it got put away, awaiting repair that it is STILL waiting for. It doesn't have any rust on it, or any pitting, and presents as new -aside from the lock problem.
So, yeah, I like the stuff. But I seem to be in the minority here.
-JP