"Rounded" Grooves or Lands at Muzzle?

[Dan]

An observation about the effects of a flawed crown on accuracy:  The adverse effect is far more pronounced on flat based bullets than patched round balls. It is also a function of exit pressure at the muzzle.  A flat based conical upset by a non-concentric crown enters an adverse nutation state which is simply not possible with round balls. In point of fact, round balls do not require spin  for gyroscopic stability, but the slow twist common to such arms does provide for an aerodynamic stabilizing factor in that it distributes the effect of minor imperfections about a single axis of rotation.

I suggest that worrying about minutiae in this context is little more than mental exercise, insofar as round ball ML guns.

[D. Taylor Sapergia]

The effect of rifling on a bullet and a ball is the same...it makes the projectile travel along a straight line horizontally.  The bullet requires a much faster rotation than a ball, to achieve this.
And a crown at the muzzle that is not perfectly concentric WILL affect accuracy of a round ball.  I state this speaking from my own experience.  I made a rifle and simply used the factory crown.  It wasn't perfect, and I could never be satisfied with the4 rifle's accuracy.  So I cut 1/4" off the muzzle, recrowned it (conventionally) and voila!  excellent accuracy.
There is no reason a person working carefully cannot create the sculptured muzzle shown several times in this thread, without ruining the accuracy of a fine shooting rifle.  I was apprehensive myself, until I tried it, with excellent results.

[Dan]

With respect, I did not say it would not carry some influence, only that the affect on round balls is less profound.  There are more ways to make a barrel inaccurate than just a flaw in the crown.  The crown of a round ball muzzle loader simply does not require the precision that is necessary for conical bullets. 

[D. Taylor Sapergia]

I concur!

[WadePatton]

O I C

thanks fellas.  I like larnin' 




(oh i see, yet shedding the ballistical entrapments of moderns)

[Herb]

Smollett, I did not do that Bridger muzzle treatment on my Bridger copy.  The rifle shoots good enough to cut strings at 100 yards.  Doc White advised me not to do the treatment.  He has built a couple thousand (his words) muzzleloaders by now, exculsive of the Green River Rifle Works and White Muzzleloaders, and you see them for sale regularly on Track of the Wolfe.  He said he has bult rifles with that muzzle treatment but it made no difference in sale of a rifle.  It was not appreciated.  His opinion is that it is not worth the trouble.  My interest in doing it was to make as exact a copy of Jim Bridger's rifle as I could.  But my barrel is two inches shorter than his, I can always say I had to cut the barrel off because I damaged the muzzle!  Incidentally, Greg Robert's (production manager at GRRW) when he traced out the Bridger rifle when it was at GRRW in 1975 noted that the muzzle is not cut square.  Though I handled the Bridger rifle at the Helena, MT museum, I did not notice that.  This is the Bridger Hawken muzzle.

Here is another original Hawken at the Montana Historical Society Museum in Helena.

[Smollett]

Herb:  SUPER!  As for the treatment not being appreciated by consumers, that is interesting.    It appears to have been quite a  common treatment on 19th century rifles.  Thank you very much for the original post I copied and for your response in this thread; both are extremely informative and greatly appreciated.

Smollett

[Acer Saccharum]

Smollett, I gulleted the grooves.

[Acer Saccharum]

My thoughts on rifling and the roundball.

The round ball does not need spin to stabilize it, since a sphere is already stable.

It does need spin so that it leaves the bore with a consistent spin, with its rotational axis parallel with the line of flight. This guarantees equal air resistance on all sides of the ball. This consistency is what allows the ball to fly true.

Think about an unpatched round ball leaving the muzzle of a smoothbore with topspin, or left or right spin. This would cause the ball to climb, or drop, or veer left or right. You'd never hit the target on a regular basis, because every time the ball leaves the muzzle, it would have a slightly different spin.

[delivered]

Don (God rest his sole) had done a couple for me with the "Butt" design!
Looks neat!