Shallow or deep rifling

[tom in nc]

After reading that some production guns, (T/Cs according to one person), do not have rifling cut deep enough, I wonder. How deep does rifling need to be? Would it differ with the caliber of the barrel? Or with the number of grooves? The purpose of rifling is to impart a spin on the projectile, right?
I just need to know how someone can look in the muzzle and say the grooves are not deep enough.

 

[diyj98]

I just need to know how someone can look in the muzzle and say the grooves are not deep enough.

I'd say they can't. I've heard various theories on rifling depth, but don't know if any of them are 100% correct. I've always figured deeper rifling made it hard to get a good seal. I always thought TC barrels were fairly well thought of.

 

[wiscoaster]

IMO if one uses a "PC" projectile the firearm that shoots it should also have "PC" rifling. This is one disadvantage of my repro 1861 Springfield that doesn't have PC rifling and therefore is not terribly accurate at shooting PC repro Minie balls.

 

[Cabincritter]

Rifling depth depends on what type of projectile the rifle is made to shoot. A general rule of thumb is that for a patched round ball, one wants deep grooves to catch and hold the patch. Rifles shooting an elongated bullet, as opposed to a ball, do best with shallower grooves. Deeper rifling will also hold more fowling, and allow one to shoot longer with out cleaning.TC used a comprise type of rifling in both twist and depth. They shoot reasonably well with either a ball or a bullet, but not particularly good with either. It is a compromise.

 

[nchawkeye]

Barrels made by Rayle, Rice, Green Mountain and others, for round ball shooting typically have cut rifling .012-015 deep.

Production guns typically are button rifled, .006-008 deep.

 

[Rock Home Isle]

After reading that some production guns, (T/Cs according to one person), do not have rifling cut deep enough, I wonder. How deep does rifling need to be? Would it differ with the caliber of the barrel? Or with the number of grooves? The purpose of rifling is to impart a spin on the projectile, right?
I just need to know how someone can look in the muzzle and say the grooves are not deep enough.

I stick my pinky into the muzzle and turn my wrist as my fingernail glides over the rifling. If my fingernail catches on the ridges of the rifling…I’m happy and it’s deep enough.