Gunsmith Or Metalurgist Question?

[moooose102]

I was cleaning my rifle last night, after being out in the snow / rain for 3 hours, and thought about this when i looked down the bore. the bore, looks, well, machined. of course it is, but how would you go about polishing it smooth, and would it be worthwhile doing so? i have seen special ammo loaded for this purpose in some calibers, i do not know if it works, or not. if it would be worthwhile or not. in any case i do not remember seeing it in 45-70 caliber. also, what about the jacket material of bullets? is this self lubricating? or does it just go down the barrel at 2 million miles per hour galling along the way. i have heard of copper fouling, i do not ever remember seeing anything that looks like copper in the bores of any of my guns. but the patches sure come out dirty for at least the first 3 or 4. i would expect the first one is probbably mostly powder residue, after that is it mostly the copper coming out? what about the thin layer of oil in the bore, i run a patch with oil on it, then a clean one to wipe out excessive oil. is this tiny bit of oil the only lube the barrel will ever see? if so, what would keep the bore from galling? i am kind of a lubrication nut, a former mechanic. i never really thought about this before, now i may have to switch to moly coated bullets in everything i own! awe crud!

 

[1911 guy]

Don't bother.

I'm assuming you've got a few rounds through the rifle. The moly bullets are, in my opinion, a gimmick. Lapping a bore serves no function if there's not a problem. As far as copper wearing on the bore, yes it does. But in most calibers, bore life is measured in tens of thousands of rounds. Copper is softer than steel, that's why you have small amounts of copper left in your bore instead of small amounts of your bore leaving with the bullet.

The pressure and velocity generated in a .45/70 is low enough that I'd expect to still be shooting the rifle accurately if you lived to be changing your great, great, great grandkids diapers. I'd be more concerned if I were shooting one of the new very fast .30's or .33's

 

[Onmilo]

Don't do MolyCoats unless you plan on shooting them and nothing else for the life of the barrel.
Mirror polishing a bore has been proven to do no real good and can sometimes lead to bigger problems when the polisher gets too aggresive and opens up the bore diameter.

You won't see copper fouling on patch material using standard barrel cleaning solvents, you need specialized solvents designed to attack and remove copper deposits.
If you actually see copper fouling in a bore, that bore is Waaaaay past useful and may actually be dangerous to fire high pressure rounds through.

Never use copper solvents in relation with a bronze bore brush, you will think that the bore is never getting clean when in fact the copper solvent is eating the bore brush and leaving traces in the bore.
Always use copper solvents with stainless steel or nylon brushes. I prefer nylon.

A .45-70 bullet travelling at 1350 feet per second is travelling approximately 960 miles and hour, not two million.

Yes, two dissimilar metals will gall, we call that "fouling".
In the case of copper jacket bullet material we call that galling action "copper fouling".

Too much oil in a barrel bore can increase pressures to the point the barrel can bulge or burst.
A thin film is recommended for rust protection and it is recommended that even this light film be wiped out with a dry patch prior to firing the weapon.

Oil will not prevent copper fouling and even if the barrel does or does not burst or bulge,,,,the oil will burn away with the first shot.

I am a gunsmith and a machinist.

 

[1911Tuner]

The .45-70 is at its best with lead bullets. More velocity at less pressure for a given load, and if you shoot the big Sharps rifles...black powder is a fascinating avenue to explore.

That said...The dirty patches are likely dirty from carbon fouling. Copper fouling will leave a greenish-blue deposit on your patches...but you have to uncover the stuff first. If you use an aggressive copper solvent, like Sweet's 7.62 or the like...follow the directions, and don't leave it soaking in the bore for more than a few minutes. I like to use a chemical copper solvent once...remove it thoroughly with patches wet with rubbing alcohol...and follow up with J&B Bore Cleaner on a tight patch. Remove all traces afterward.

Unless the bore is heavily fouled with copper, you really don't need to be that aggressive, though. The best medicine is in the prevention. Cleaning the bore with a good solvent like Shooter's Choice or Butch's Bore Shine every 10 rounds or so will keep your rifle happy.