Shiloh Rifle Forums

Not really a gain twist, but a very distinct change in pitch about 3/4 of the way down the barrel to a visibly faster twist. The transition is supposed to shatter the patch for a clean release since the smooth rifling will not cut the patch. Without this feature, I don’t see how the patch could get a quick clean release from the bullet.

So it had an abrupt pitch change mid barrel ? I'd sure like to see an example of that as I heard this before but was not sure I understood what was being conveyed.

I got into this some years back and read up on Medford's rifling and what I came away with is he used polygonal rifling with a gain twist to break up the patch not an abrupt pitch change mid barrel . I don't see how that would be practical when gain twist would accomplish the same end.
If I under stood this correctly than my guess is that the confusion is probably from the term segment-al rifling.

Fwiw, there are 2 kinds of Metford Rifling. The earlier is a form of multigroove rifling, and the 2nd segmental. And yes, as made by Metford it was gaintwist.
Mine isn't, but patch release isn't an issue. Lancaster oval bore was also used with pp, and worked quite well.

I was thinking that if it shoots GG bullets well but not PP, maybe the lack of a twist change might be the problem. If it were my rifle I would try slitting the patch on opposing sides with a razor and see if this helps the patch to clear the bullet quickly. To clarify, slit after the bullet is seated in the case.

You might also pick up the fired patches, with and without slitting, and observe their conditions and distances from the muzzle.

The other thing that needs to be remembered is that in gain twist the lands and grooves change width as the pitch increases toward the muzzle which would also help break up the patch.

It actually might be more a fouling problem, as usually the 1st few shot with PP bullets shoot just fine, after shots 5-7 (depending),they start spreading... I once had issues due to uncorrrect cleaning technique with this barrel, so I firelapped it in order to get it back smooth. However, it still might be a bit too rough for PP. GG usually will support barrel roughness easier than PP.

Firing lapping works pretty good for a few inches up bore and I have used it in both rifle and revolvers but lead slug lapping is the best for longer barrels.
Lead slug lapping cannot be used in a gain twist but leather washer lapping can. As you have a even twist a good lap job will probably help and will never hurt if accomplished correctly.
The fire lap works very well in revolvers to get rid of the usual tight bore over the frame threads ahead of the forcing cone.

how far out are your patches when you fire?? is it like little strips or big chunks??