Polygon groove barrels for ball?

[gunsports]

Has anyone tried, or made, a slow twist polygon grooved barrel for ball? First off, I am a student (and admirer) of Lt. Forsyth’s slow twist, shallow groove, narrow land barrels for ball and am in the process of acquiring two of these barrels to build rifles on.

To my way of thinking, a polygon groove would/should work very well for a ball barrel; especially in the very slow twists that Forsyth advocates.

Has anyone tried this and what, if any, has the success rates been.

Any thoughts on the matter?

[Rasch Chronicles]

Interesting question.

I remember Forsyth used a slug, and got excellant accuracy. It worked in the HK with modern projectiles, I wonder now, how it would do with a ball, assuming appropriate twist.

Best regards,
Albert “The Afghan” Rasch
The Rasch Outdoor Chronicles
Feral Bull Fighting: Another Chronicles Adventure!

[Dphariss]

I assume you mean 5-6-7 sided much like the Whitworth.
Poor choice for patched roundball.

Dan

[Dphariss]

Interesting question.

I remember Forsyth used a slug, and got excellant accuracy. It worked in the HK with modern projectiles, I wonder now, how it would do with a ball, assuming appropriate twist.

Best regards,
Albert “The Afghan” Rasch
The Rasch Outdoor Chronicles
Feral Bull Fighting: Another Chronicles Adventure!

Forsythe wrote of explosive shells, not slugs. He considered the conical and its various incarcerations to be worthless as a hunting bullet.

Dan

[Rasch Chronicles]

Oops!

Dan, you're right of course. I'm woking off of memory, and I really should look stuff up before I write. 

Best regards,
Albert “The Afghan” Rasch
The Rasch Outdoor Chronicles
Feral Bull Fighting: Another Chronicles Adventure!

[gunsports]

Please allow me to expand a little on my thinking here …

First of all; polygon groove rifling may, or may not, qualify as ‘traditional’ in the true sense of the word. But, I walk in the company of giants as regards knowledge of all things muzzle loading and your comment, and expertise, will be greatly appreciated.

To my way of thinking, a smooth bore barrel, well fitted with ball and patch, produces the best velocity per given load, at the lowest pressure for that load. Unfortunately, the smooth barrel lacks the ability to give stabilizing rotation to the ball, thus reducing accuracy, especially over the longer distances. With the addition of very shallow grooves, at a rate of twist just sufficient to impart stabilization to the ball; the benefits of a smooth barrel is retained, with the added benefit of superior accuracy. This is/was basically the conclusions reached by Forsyth; after extensive experimentation and field testing.

Now, if one can dispense with the need to groove the barrel, but in its place, cut the barrel with a poly groove similar to that used in modern gun barrels: i.e; very shallow ‘grooves’; one could theoretically, improve even further on Forsyth’s barrel design.

The poly groove should give superior sealing (much like it does to modern jacketed bullets) of ball and patch; very close or equal to, a smooth barrel; the slow twist will give rotation to the ball and the lack of sharply defined lands will obviate the risk of the ball and patch stripping on the lands under heavy charges of powder.

I am keen to make such a barrel but, before I commit to the project, I would appreciate some expert opinion.

[T*O*F]

I think you are referring to "Paradox" rifling where a smoothbore is rifled with a very slow twist for the last few inches of the muzzle.  It was used for slugs, which obturate, instead of round ball.

Alternatively, I have a smoothbore which is "scratch rifled" and I never knew it until I changed out the touch hole liner and examined the bore while the breechplug was out.  There are 3 faint grooves which are not evident if you drop a bore light down it and look from the muzzle.

[Daryl]

I believe he's thinking of the multigroove barrels like Marlin uses - ie; in their 'polygrooved' barrels, 12 very shallow grooves are cut, which spin the bullets just fine - but they are not polygon, but polygroove -  this apprears to mean  multigrooved to Marlin.

Rifling a choke, aka Paradox might work but they do need to be deep, and since we're loading from the muzzle, the ball and patch must pass through the choke first - sometimes this works, sometimes not.

 With Forsyth's slow twists, the grooves can be shallow anyway and multigrooves are then not necessary to spin and hold the ball/bullet.

In the Ctg. gun,  very shallow rifling required many grooves to hold and spin the bullet.  The fewer the grooves, the deeper they needed to be. 

In the ML, with shallow rifling and slow twist, the ball's needs are met with a moderate patch.

[Daryl]

The polygon shape, as Pac-Nor and some other makers are playing with in modern barrels is very similar to the Hexagonal rifling of the 19th century Whitworths - as Dan rightfully noted. i agree that it is not a good shape for round ball - imho - but perhaps someone needs to try it on Forsyth's principal - very slowly twisted.

[Dphariss]

Please allow me to expand a little on my thinking here …

First of all; polygon groove rifling may, or may not, qualify as ‘traditional’ in the true sense of the word. But, I walk in the company of giants as regards knowledge of all things muzzle loading and your comment, and expertise, will be greatly appreciated.

To my way of thinking, a smooth bore barrel, well fitted with ball and patch, produces the best velocity per given load, at the lowest pressure for that load. Unfortunately, the smooth barrel lacks the ability to give stabilizing rotation to the ball, thus reducing accuracy, especially over the longer distances. With the addition of very shallow grooves, at a rate of twist just sufficient to impart stabilization to the ball; the benefits of a smooth barrel is retained, with the added benefit of superior accuracy. This is/was basically the conclusions reached by Forsyth; after extensive experimentation and field testing.

Now, if one can dispense with the need to groove the barrel, but in its place, cut the barrel with a poly groove similar to that used in modern gun barrels: i.e; very shallow ‘grooves’; one could theoretically, improve even further on Forsyth’s barrel design.

The poly groove should give superior sealing (much like it does to modern jacketed bullets) of ball and patch; very close or equal to, a smooth barrel; the slow twist will give rotation to the ball and the lack of sharply defined lands will obviate the risk of the ball and patch stripping on the lands under heavy charges of powder.

I am keen to make such a barrel but, before I commit to the project, I would appreciate some expert opinion.

First.
A very smooth barrel, lower friction, does not necessarily mean higher velocity.
The English used to rough the first few inches of a ML  shotgun barrel to increase velocity.
Blackpowder will make more pressure when it has increased resistance.
One of the  reasons that GM barrels seem to shoot well with large charges may not be that the 70" twist is a 50 for example but that the lands are narrow and may produce less friction.
So the easier the ball moves the less efficiently it uses the powder.
This is why the larger bore rifles use the powder more efficiently than the smaller bores do.
The old timers used to claim that a barrel could shoot slick and needed to be etched to restore accuracy and they would, I have read, plug the nipple and poor the bore full of urine.

I believe that the current fad of polygonal rifling is just something the make the guns different.
If it were is anyway superior the serious competitors in bench rest and other precision shooting sports would use it.

I do not believe it will work well with a cloth patched projectile in any case. I think its too difficult to seal the "corners". To work well the ball must be  engraved with the lands and the patch fills the grooves. Narrow lands allow starting a tighter ball/patch fit.
Really narrow and/or really deep grooves are very difficult to seal the really narrow grooves , i.e. wide lands, load hard.

In a rifle shooting a long bullet 2-3+ calibers,  the high inertia of the bullet can replace bore friction and the heavier bullets fired with BP will expand to fill any bore shape.

Dan

[Don Getz]

That polygon shape of a bore was strictly english, and was not meant for round balls, but rather it shot a bullet that was
shaped the same as the bore.    It is somewhat rare to see a gun with this bore shape, so, apparently it didn't set the
world on fire.  It was a rifle that was built in the mid 1800's when a lot of things were going on in muzzleloading guns,
but came to a halt when they started to build rifles where you would stick everything in at the breech.  I can't imagine
how you would shoot a round, patched ball out of a bore like that.............Don

[gunsports]

Thank you for the advice. You saved me a lot of time, bother and expense making that barrel.

[Daryl]

Don might have something there in 'made to test a theory or merely for something different' - the polygonal bores - mostly on pistols - might have been a "hey - I was reading about this form, so I made a barrel and it shot reasonably well, so we made a few for sale".

[FL-Flintlock]

I think there's more confusion in the definitions than anything.

This is Polygonal rifling - no sharp edges or straight-cut lines and typically having 4-8 of what we'd associate with being "grooves".



Whitworth is a true Hexagonal bore having six straight-cut flats.



Paradox is not a rifling but rather a manner of combining a smooth and rifled bore where only the last 2-3 inches of the bore are rifled and typically done with some variation of Ratchet style rifling.



Modern shooters will most associate the term "Polygonal rifling" with HK's and Block's and associated warnings against using cast bullets in those bores but truth be known, all rifling is "polygonal" since the term merely describes a closed shape and not a particular style of groove or shape.  The modern termed "polygonal rifling" is nothing new or even modern, the style of rifling devoid of sharp or otherwise well-defined grooves pre-dates standard square cut-groove rifling.

The problem with cast bullets and other-than-cut-groove style rifling is typically concerning the deposition of lead caused by the use of incorrectly sized bullets where blow-by or excessive extrusion are the root causes resulting in what amounts to creating a bore obstruction.

The depth of the grooves, no matter what shape they are, is only one concern in the overall barrel.  If you go back to when Marlin started using the Micro-groove rifling there were a lot of concerns about it not working with anything other than low-velocity jacketed bullets yet that style of rifling has proven itself to be exceptionally accurate shooting with all kinds of bullets from the soft bare lead .22LR to the so-called "premium" copper to the bi-metal jackets.  It's like anything else, each style of rifling has its benefits and drawbacks which often depend more on who's doing what to the loads they're stuffing in the barrel. 

[Rasch Chronicles]

FL-Flintlock,

I've been mulling the same thing all day here. "Why, wouldnt a ball and patch combination not work in a polygonal bore?"
If the ball and patch combo wasn't tight enough, I could see some problems. But otherwise I don't know what might cause an issue. It would be interesting to find out though.

Regards,
Albert A Rasch
The Rasch Outdoor Chronicles
Wild Pigs: Not Tough Enough to Face Ol' King Coal

[Daryl]

FL-Flintlock,

I've been mulling the same thing all day here. "Why, wouldnt a ball and patch combination not work in a polygonal bore?"
If the ball and patch combo wasn't tight enough, I could see some problems. But otherwise I don't know what might cause an issue. It would be interesting to find out though.

Regards,
Albert A Rasch
The Rasch Outdoor Chronicles
Wild Pigs: Not Tough Enough to Face Ol' King Coal

The ball and patch combination would have to be very tight - but we're used to that, up here. As noted above, built on Forsyth's principal- 24" to 26" tubes, 1/4 turn, it might work just fine.

[Don Getz]

Albert........where are you going to find a barrel with a bore like the second one down?   Just off hand, I don't know of anyone doing a bore like that, and, being a former barrel maker, I would not make you a barrel like that...........Don

[FL-Flintlock]

The patch/ball combo need not be made any tighter than is necessary for any other bore.  If you're getting a seal, it's tight enough to grip - remember the style isn't all that different than some of the round-bottom rifling that's been both praised and cussed in the ML community.  I had a round-bottom barrel someone insisted needed replacing because "That #$@#$% thing won't shoot!".  Well, perhaps that person was right since the lady who now has it couldn't get it to do any better than this at 75yds.



Look back in history and there's been all sorts of methods of getting spin on the projectiles, some were nothing more than a twisted oval shaped bore and others were insanely complex like the one done with grooves that sort of looked like the letter "W".  The common modern rifling termed "polygonal" came about primarily as a way of reducing the time, and subsequently the cost, of hammer-forged barrels since the style permits the allowance of far greater tolerances than would otherwise be acceptable or safe in a bore having standard square-groove style rifling.  There was also a lot of fuss made about the number of grooves until reality proved that a two-groove barrel is more than capable of shooting just as good as a six-groove or eight-groove.

Don,
There's still a few shops the will make a Whitworth hexagonal bore but they're so problematic with fouling that hardly anyone wants one to actually shoot with.  I know a fellow who had three of them made, they'll shoot if you take the time to swab the bore perfectly clean for each shot.  BTW, ratchet rifling is starting to make a strong comeback in the centerfire arena.

[Acer Saccharum]

Just off the top o' me head: the more facets you have the closer to round bore the barrel will be. A ten sided polygon bore would probably work with round ball. A square bore would not work with round ball.

Why would the number of sides make a difference?

Gas sealing. With a square bore, you'd never get a ball/patch combo to fit tightly in the corners. With ten sides, the ball and patch will fill the corners much easier, and the bore has enough bite to spin the ball properly.

Tom

[Dphariss]

Just off the top o' me head: the more facets you have the closer to round bore the barrel will be. A ten sided polygon bore would probably work with round ball. A square bore would not work with round ball.

Why would the number of sides make a difference?

Gas sealing. With a square bore, you'd never get a ball/patch combo to fit tightly in the corners. With ten sides, the ball and patch will fill the corners much easier, and the bore has enough bite to spin the ball properly.

Tom

I have seen seven sided bores on American rifles. I had a restocked barrel once in 36 caliber that was rifled in this manner. It was also turned for a starter. I was too young and ignorant to check it out properly and it got sold off. Before I was drafted or after I got back?
They have grooves cut into the corners. I have an illustration of this somewhere. Maybe in Dillion's book. I think it was found on some German rifles too.
The problem will be that the the barrel will load hard if loaded tight enough to get much of a fit in the  corners.

Dan

[Rasch Chronicles]

I remember reading about a two groove bore for ball, where the ball had a waist band to ride in the grooves. Sort of looked like a fat Saturn (The planet, not the car!)

Best Regards,
Albert “Afghanus” Rasch
The Rasch Outdoor Chronicles: George Washington, President and Fisherman

[FL-Flintlock]

I remember reading about a two groove bore for ball, where the ball had a waist band to ride in the grooves. Sort of looked like a fat Saturn (The planet, not the car!)

Best Regards,
Albert “Afghanus” Rasch
The Rasch Outdoor Chronicles: George Washington, President and Fisherman

The "banded" or "belted" balls were created not long after Pyotr Alexeyevich Romanov (a/k/a Peter the Great) founded the official State arms factory at Tula but when it was found that they couldn't produce reliable consistent accuracy, they quickly went away  and stayed away until the Brit's resurrected it in the 1830's, IIRC, with the Brunswick rifle.  Interesting note is that the Brunswick had the band/belt oriented in the direction of travel plane or with the belt leading and trailing as the ball flies.  This is often misidentified as a "winged" ball but should not be.  There were a multitude of "winged" ball designs from the mid-18th century typically having three to six individual protrusions or wings placed symmetrically around the equator of the ball oriented in the same manner as the belt on the ball shown below.  The wings mated with either straight or twisted grooves in the bore and were oriented in the vertical plane as the ball flies - note that all these designs were also scrapped because of loading and accuracy issues.  The belt-leading Brunswick ball again proved to be difficult loading and inaccurate at range.

Greener again resurrected the vertical plane belted ball design only to learn that it was still worthless nearly two centuries after it had already been proven a failure.  I'm not sure when it was given the name "paradox ball" but following Greener there were numerous attempts to continue using similar designs in cartridge loadings.  Often you'll find some of the later ones presenting many individual wings or having slanted slots in the belt which were touted as "air rifling" - despite the sales hype about the so-called "air rifling", the projectiles were launched in the supersonic velocity range whereby the wings, grooves or otherwise did absolutely nothing except disrupt the flightpath just as had happened with all the other belted and winged balls.

[Acer Saccharum]

That belted style bullet can roll down the barrel AND twist at the same time, which will lead to unpredictable trajectory.

[FL-Flintlock]

That belted style bullet can roll down the barrel AND twist at the same time, which will lead to unpredictable trajectory.

Other than Greener and the other cartridge gun applications, I don't believe any belted balls were used in smoothbores.  In ML applications where the belt was oriented perpendicular to the bore plane, the ball was set on the muzzle then smacked to swage the belt to the bore.  I've not read, or at least don't recall reading, anything that specified the loading issues - one could reasonably conclude that when being evaluated, orienting the belted balls correctly in the heat of battle would likely be the primary issue.  Starting the ball square to the bore could also be problematic in a paper cartridge configuration as one wrinkle of paper could cause it to start out of square.  Orientation but more-so buggering the ball belt on loading was the primary issue with the parallel to the bore orientation of the Brunswick rifle.  Nonetheless, even when orientation and loading issues were resolved by putting the belted balls in cartridges, they still suffered from poor accuracy.

[Dphariss]

I remember reading about a two groove bore for ball, where the ball had a waist band to ride in the grooves. Sort of looked like a fat Saturn (The planet, not the car!)

Best Regards,
Albert “Afghanus” Rasch
The Rasch Outdoor Chronicles: George Washington, President and Fisherman

The most wide spread use of the belted ball was the result of many English and some other European's believing that the larger the ball the faster the twist had to be. This resulted in "bore" rifles with twists so fast that any charge of powder that would make the rifle useful for heavy game they would blow the patch. The answer? Fitted balls like the belted thing. I suspect they were shot patched. But I have no information on the loading of the Brunswick rifle etc. but I doubt the belted ball was shot "naked" it would have leaded and the lack of a patch with lube on it would have produced very hard fouling unless a lubed wad was used under it. It would also be difficult to keep it in the bore unpatched.

Sir Samuel Baker used one but the disadvantages already enumerated were noted by hunters like Forsythe who advocated shallow grooves and narrow lands coupled twists that many makers simply refused to accept as usable.
The silly part in all this is that the 20 bore Baker rifle was a slow twist with "modern" rifling and worked very well. There were writings in the 1830s in England that expounded on very slow twists. They also knew the "small bore"  American was a slow twist, but the one turn in the barrel was very close to 48" in the long barreled American rifle.  But they still ended up making short barreled heavy game rifles with one turn in a 24-28" barrel. The high inertia of the large ball was not able to start turning rapidly under initial acceleration (IMO) and the patch blew. So the powder charges were cut back to anemic levels.
Today we are hampered by the fact that we don't know the ball size, bore size, rifling form and patch used in examples such as this...
Forsythe writes:
"A Purdey rifle I once possessed, 13 bore, with a turn in 3 ft. 6in., invariably stripped if I gave it the least thing more than 1 3/4 drachms :---with that charge, it shot splendidly, but the elevation was excessive, the rise in its 100 yard trajectory being 11 inches, rendering it utterly useless and absurd for sporting purposes, that is, for shooting game in the field.

I think part of the problem was shooters in ENGLAND not wanting to use the charge of powder that would give accuracy with the slower twists they also liked light rifles. This needed powder charge was often far above what a shotgun of similar bore size would use. 5 to 6 drams (or even more) in rifles of 16 to 12 bore.

Dan