Of the two products mentioned I would prefer LMF. But, I have discovered another product that works better, and is cheaper. A friend wanted to build his first muzzleloader. Instead of taking a traditional path, with a good grade kit, he decided he wanted to build a gun from purchased parts, and a carve it from a stock blank. I know this sounds like a formula for disaster, but being successful metal fabricator, and artist, he pulled it off beautifully. When it came to the metal finish, I prescribed several different products, all of which he tested, and decided against. He used an blackening chemical that he had in his shop that when used like other browning agents put down a reddish brown finish with an incredibly fine grain. So I would check out the local fabricator and see what he has. I don't recall the brand name of this product, but am sure there are several manufacturers that make a similar product. The best part is a pint of this stuff costs about the same as a small bottle of everybody else's product.
Hungry Horse