Why three groove rifling on military arms?

[m1garand_man]

I have wondered for a very long time what the logic behind three groove rifling on military muzzle loaders and later arms was. As I'm are you are all aware the lands and grooves on the rifling I'm talking about are equal width. It seems to work just fine, but how did they arrive at that configuration and why?

[Clowdis]

Probably had something to do with the fact that you could cut them quicker than 7 grooves. Both versions were tested at Harpers Ferry and both performed well. The 3 grooves were also tapered depth starting about .012 deep at the breech and tapering to about .005 deep at the muzzle. The shallower depth was thought to make the minie balls more aerodynamic by creating less of a "wing" on the base of the bullet.

[rich pierce]

I have wondered for a very long time what the logic behind three groove rifling on military muzzle loaders and later arms was. As I'm are you are all aware the lands and grooves on the rifling I'm talking about are equal width. It seems to work just fine, but how did they arrive at that configuration and why?

We are focused on the longrifles here. Later arms are not a focus.

[Seth Isaacson]

My understanding is that it is easier and cheaper to cut three grooves than more and that they still provide sufficient accuracy. I wonder if it was found that they are easier to clean too?

[smart dog]

Hi M1,
Rich is right that we do not deal with firearms later than 1860.  However, the model 1855 Springfield rifled musket does squeak under the wire.  I believe the 3 shallow grooves were designed to: 1) enable the hollow based bullet to make a good gas seal when fired, 2) provide easy loading and cleaning, 3) be cheaper to manufacture.

dave

[m1garand_man]

I have also seen this on p53 Enfield muskets. Sorry for the ruffled feathers. I figured rifled muskets were a go for discussion. I didn't realize there was a  1850 cut off.

[Pukka Bundook]

The P 51 was four groove, and it was deemed that the projectile was not as stable as it should have been.  Something to do with the four -way expansion.  (I forget the details.)
The P '53 was as we know 3 groove, and the problem was solved.
Keeping this short as the ice is a little thin.  :-)

[Tim Crosby]

I have also seen this on p53 Enfield muskets. Sorry for the ruffled feathers. I figured rifled muskets were a go for discussion. I didn't realize there was a  1850 cut off.

 1860. The emphasis is on Long rifles.

 "The mission of AmericanLongrifles.org is to promote, preserve and support the traditional art and craft of building, collecting and using the American Longrifle. This would include accouterments and related arms of the period.

While the term American Longrifle may include a large and diverse group of firearms including those made for military and experimental reasons; the focus of the board is only those arms made primarily as sporting arms and utilizing a side lock ignition system."

  Tim C.
 

[Tanselman]

I realize this discussion started with a military-style, rather than civilian, muzzle loader. But the general premise of 3 grooves being superior to 4 grooves is an interesting discussion. I have wondered why civilian gunsmiths decided on different numbers of lands/grooves...always a presumption on my part they somehow thought it provided more accuracy...giving them a leg up on the competition.

       In Kentucky, where I research, the fine Bardstown rifles made in the 1810-1835 period by Jacob Rizer and David Weller, always had six groove rifling...unless recut at some later time. Why would some of the finest rifles made in KY have six groove rifling, when all the other Kentucky major markets, such as Lexington and Louisville, used the more traditional seven groove rifling? You hear old stories that rifles are more accurate with a land directly across from a groove, leading to an odd number of grooves. But why would one of the very best makers then decide to use six grooves, when he must have heard those same old stories? It makes identifying their plain guns easier...but there must have been a better reason than "just personal preference" originally.  Shelby Gallien
 

[Levy]

I think there was some discussion on the ALR a little while back about Postley barrels having 4 grooves.  I have a four groove Postley barrel on a back action half-stock squirrel rifle.  James Levy

[Bob Roller]

N.G Whitmore cut 12 grooves and his rifles were legendary for accuracy.

Bob Roller

[JCKelly]

Experimental work at the time showed 3 grooves in a tapered bore worked best for hollow base bullets, e.g. Minie or Pritchard (spel?). Most round ball rifles used more grooves.

For the non-longrifle stuff read: Report of Experiments with Small Arms for the Military Service by Officers of the Ordnance Department U.S. Army, H.K. Craig ©1856   I believe Mr. Davis was Sec'y of War at the time.

[Carney Pace]

I realize this discussion started with a military-style, rather than civilian, muzzle loader. But the general premise of 3 grooves being superior to 4 grooves is an interesting discussion. I have wondered why civilian gunsmiths decided on different numbers of lands/grooves...always a presumption on my part they somehow thought it provided more accuracy...giving them a leg up on the competition.

       In Kentucky, where I research, the fine Bardstown rifles made in the 1810-1835 period by Jacob Rizer and David Weller, always had six groove rifling...unless recut at some later time. Why would some of the finest rifles made in KY have six groove rifling, when all the other Kentucky major markets, such as Lexington and Louisville, used the more traditional seven groove rifling? You hear old stories that rifles are more accurate with a land directly across from a groove, leading to an odd number of grooves. But why would one of the very best makers then decide to use six grooves, when he must have heard those same old stories? It makes identifying their plain guns easier...but there must have been a better reason than "just personal preference" originally.  Shelby Gallien

they may have had to make the guide by hand.
It would be easier to lay out and cut a rifling guide using 6 grooves, even number rather than odd number.  6 grooves would be 60 degrees apart. 
Probably no other reason.   

Carney