Lands and Grooves

[oldfrank]

I recently found a little skinny light that I dropped down the barrel of my Lyman Trade Rifle. It was pretty interesting to see.

Now the lands are all smooth and shiny but the groove looks like it has lines all running through it.

Am I correct in thinking that is from when the barrel was made or is that a result of poor cleaning?

Thanks!

 

[Rifleman1776]

Am I correct in thinking that is from when the barrel was made

Yes.

 

[Billnpatti]

The usual procedure for barrel makers is to polish the bore after it is bored. Then the grooves are cut. Often this is done by pulling a button through the bore to cut the grooves. The result is smooth lands but tool marks in the grooves.

 

[M. De Land]

Most muzzle loading barrels are usually cut by broach or a hook cutter because when shooting patched round balls the grooves need to be deeper than when shooting greased lead and a carbide rifling button pretty well limits out at .004 in depth producing ability.
Most barrels cut for patched round ball will have grooves of .008-.012 in depth.
The bores are reamed after deep hole bored to bring them up to ID spec and to smooth them some what. The high end barrels will be lapped to get out the reaming scratches and then rifled.,
The hook or broach cuts steel in a chip shear fashion which leaves a knap in the grooves that show up as longitudinal scratches.
This will abate with time and use as the groove bottom polishes out from the patch abrasion/polish action.
Hand lapping after rifling can greatly aid this process as well.

 

[oldfrank]

I feel better now. Thank You all!

 

[Richard Brinkman]

It's a lot better to have the longitudinal scratches in the grooves that to have what looks like railroad tracks on top of the lands.

RB