Number of grooves

[gemmer]

All the muskets I have had relined were done with three grooves. I see mention of relines done with five or seven grooves. What advantages do they have over a three groove barrel?

[R. McAuley 3014V]

There is no reliable evidence that having more lands touching a bullet does anything. But one way to look at this has more to do with the surface area that the lands are touching on a bullet and how much less the amount of friction may be with a multi-groove (i.e. 6, 7, 8-groove) rifling than with the traditional 3-groove rifling. Obviously, the greater the number of lands, the smaller surface area that is touching the bullet, hence how much the lower the frictional forces acting on the bullet. Bullet stabilization has more to do with the internal ballistics or dynamics of the bullet design than with the rifling, though certainly having a greater number of contact points on a bullet might assist in its stabilization. The standard 3-groove rifling was simply the most economical, though obviously 2- and 4-groove was also used.

[Jim Brady Knap's Battery]

I believe Mr. Burton's experiments at Harpers Ferry showed a preference on three grooves for rifle muskets. His reports are very interesting and can be found in a book titled Small Arms 1856. It shows that every rifling style, bullet design, and powder charge was done with a reason and economy doesn't seem to enter into the final choices. The book also has some reports on experiments in some European countries.

Amazon has a few showing https://www.amazon.com/Small-Arms-1856-Experiments-Military/dp/0939631016/ref=sr_1_1?ie=UTF8&qid=1505960849&sr=8-1&keywords=Small+arms+1856

[Phil Spaugy, 3475V]

https://books.google.com/books?id=YXkDAAAAYAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Here is a link to the online copy of the book Jim is referring to.

[Charlie Hahn]

When looking at built groove barrels I believe it is more important to decide if you want equal groove and land width. Next is rifling depth. Tis is a function of the bullets ability to form into the entire barrel surface and limit the gases from blowing by the bullet and causing leading.

When looking at the 7 L&G barrel I have found that a narrow land and wider groove has and advantage, (Pope Style). The bullet when fitted correctly can touch the bottom of the groove and pre-engrave on the edges of the land. Helps with pre-load when the ballistic event begins. Can be finicky to load if your lube is not consistent.

If you use equal/equal L&G, the depth of the rifling needs to be looked at, and shallow is better, however the material of the barrel needs to be a little harder to keep the edge of the land from washing out.

I have muskets with several combinations I am developing. Not sure I am really doing anything that has not been done by the old masters, but still looking for the optimal for our sport.

These include, 5 x 5, equal L&G with a gain, similar to one of Burton's test designs

7 x 7 equal L&G very shallow in 4140G full length tube constant twist.

3x3 equal L&G shallow depth in SS.

7x7 equal L&G deep rifling, (older design from Ray Goode 1972) 4130 steel.

One in slow twist high velocity light bullet.

Mr. Hoyt has been kind enough to tolerate my requests and is making barrels and liners from 86L20 to help with torque, (barrel whip) that I an developing.

I do believe any combination will work, I am hoping to find one that will stay constant over time.

I know this is much more information than asked for in the original question, but there are so many more considerations that need to be addressed when looking at the barrels we use, and is offered as ideas for discussion.

Charlie Hahn

[Wayne Shaw, 1985V]

Harry Why don't you stop into the SAC office (you know where it is) and ask! Open Wed Thurs Friday 9:00 to 11:00 We will be able to answer your Question !!!!! Wayne Shaw National IG and SAC

[hobbler]

Thinking back to reading the papers on small arms development, three groove was chosen over five or more at least in part for the same reason as slower twists, because of wanting to minimize spin induced lateral movement of the bullet that showed up at long ranges. Having an odd number of grooves was preferable for manufacturing and fewer grooves meant less sideways thrust being induced while the spinning bullet was pulled downwards by gravity and it's forward momentum slowed by atmospheric resistance.