freshen barrel?

[Trot]

Well, I don't know about re-rifling, just sort of clean up the rough spots on what is there. I have actually worked on it a bit, and I think it is better but I haven't had a chance to try it yet.

 

[shootrj2003]

I hope he never took it to a Gander Mt. gunsmith.

 

[M. De Land]

I seem to remember that H M Pope often used gain twist, but don't remember if he also use a little muzzle choke. Some where there's a book on Pope barrels that might have some discussion. Mine is stored in a box someplace

rayb

Pope was not really muzzle loading for the most part of his shooting career but rather seating the bullet through a false muzzle into a breech-ed , charged case. He did use gain twist and choke. Pope by the way did not but choke into his barrel but instead lapped it into them. Pope also liked left hand pitch (he shot right handed) as it torqued the rifle into his cheek instead of away from it. By the way the torque direction is the same as the pitch direction, not opposite as some folks insist. The reason is because the bullet friction on the rifling pulls the barrel pitch with it as it goes up bore. Newtons third law does not apply as some folks think.

 

[M. De Land]

Pope was not really muzzle loading for the most part of his shooting career but rather seating the bullet through a false muzzle into a breech-ed , charged case. He did use gain twist and choke. Pope by the way did not but choke into his barrel but instead lapped it into them. Pope also liked left hand pitch (he shot right handed) as it torqued the rifle into his cheek instead of away from it. By the way the torque direction is the same as the pitch direction, not opposite as some folks insist. The reason is because the bullet friction on the rifling pulls the barrel pitch with it as it goes up bore. Newtons third law does not apply as some folks think.

I used the word choke in the last post but more correctly should have said taper. Pope actually made a set of graduated, tapered diameter bore slugs, one inch long which was fit to it's predetermined depth, this accomplished by lapping to fit depth not mechanically cutting it as some have said. Each slug a bit larger was fit to the added length of barrel until the whole interior had been tapered it's full length. The depth of lapped taper we are talking about here are very small and in the ten thousands range. Frequent, freshly pored laps will maintain sharp rifling profile ,contrary to what some believe.
The reamed bore is the bed for the rifling head and cutter used in this period, all of which was known as single point cut rifling. The cutter was of either the hooked or scraping profile.
Before this technology evolution the grooves were cut with a graduated saw cutter fit into the slot of a hard wood or lead cutting head. The cutter was elevated by paper shims. This saw with it's row of teeth in line was actually the early equivalent of a modern day broach but only cut one groove at a time where as a broach cuts all the grooves at once. The same was used to "freshen" a barrel.
Other barrel makers such as Warner and Brockway of the period would cut the grooves with the single point method then lap a barrel level until the final three inches and would put taper in only this section which is more correctly described as choke. They found this method produced the same level of accuracy with much less effort.
An interesting quirk of gain twist rifling which also was employed by a few who thought it beneficial to accuracy is that the land width narrows and the groove widens gradually toward the muzzle. The reason for this is because as the pitch increases the cutter profile ,static angle, broadens. Think of a square or rectangular profiled cutter being pulled straight ahead now rotate that shape slightly on a central axis, the profile broadens and it will cut a wider path. This is what is happening as the pitch increases in a rifling head.
The thing about gain twist is that on a conical bullet the front is always progressively out turning the base producing a certain amount of increasing skid or stripping action. With a patched ball the rifling does not directly contact the projectile and the contact area is so short that is does not have the same effect.

 

[Woody Morgan]

Another option re: lapping is using compound on an unmentionable rifle or shotgun mop. It would conform to the barrel interior dimensions pretty well.

wm

 

[M. De Land]

Another option re: lapping is using compound on an unmentionable rifle or shotgun mop. It would conform to the barrel interior dimensions pretty well.

wm

The lap slug needs to hold the land corners of the rifling sharp and a mop will not do this. When I hand lap I cast a new slug every 250 round trips up and back and recharge the existing lap every 50 round trips. This will maintain a sharp land top corner profile and lap the bottom of the groove as well as the top and sides. Round groove bottom rifling does not mean the land top corners are round nor should they be for top accuracy.

 

[M. De Land]

Another interesting quirk I leaned somewhere along the way about single point hooked or scrape rifling is that the groove depth at entry and exit of the barrel being rifled will be shallowe in both ends. The reason is the cutter is being supported on both sides of the riling head while both are still in the reamed barrel interior. As one side or the other of cutter in the riling head are still clear of the reamed bore and unsupported while entering or exiting the groove depth is made shallower untl both sides of the cutter are again supported.
This can be used to advantage at the muzzle as it will choke the groove depth. The reason tapering and choking general contributes to accuracy is because the graduated resistance to bullet passage pulls on the barrel linearly and dampens barrel whip at ball/bullet exit.