Polygonal rifling

[flintster]

Hi Guys,  I have a question regarding polygonal rifling on a muzzle loading rifle. Has it ever been tried and what were the results. Seem like a good compromise between a smooth bore and a rifled barrel. Easy to clean and load and still accurate. Forgive me if this seems a stupid question but this type of rifling has worked very well in cartridge guns. Thanks for any response.

[rich pierce]

I've got a John Getz barrel with what I guess is polygonal rifling. Haven't built and shot it yet.

[Bob Roller]

I've got a John Getz barrel with what I guess is polygonal rifling. Haven't built and shot it yet.

Polygonal rifling? Think WHITWORTH with the hex bore and bullets to match. Nothing new
about it.

Bob Roller

[Hungry Horse]

The polygonal rifles used during the Civil War experienced rapid barrel wear. Leading to a rapid drop off in accuracy.

  Hungry Horse

[Daryl]

Some Euro Air rifles are now using a polygonal-type rifling, they call invisible rifling.

Pac-Nor, the modern rifle barrel company in the States used to make or maybe still does make polygonal rifling.

One of the Euro 9mm's had polygonal rifling. Seemed many people rage about it for a year or two - then nadda.

I wouldn't expect it to wear any more quickly than any other rifling, or maybe not as quickly, however, how deep the rounded grooves were from the rounded lands, I do not know.

Lancaster made what might be called polygonal rifling in some of the DR's back in the 1880's- called it invisible rifling, but the grooves, wide as they were, were actually about .010" deep and actually displaced a lot of metal and shot well enough, I guess.  They were popular for a time.

[James Wilson Everett]

Guys,

Years ago i made a pistol with a polygonal bore barrel.  It was seven sided, and I called it my "Whitworth" barreled pistol.  The barrel was a lot more work than a normal seven groove barrel as there is probably 3 times more metal to cut out in the rifling process.  I could find no advantage to this, but it was interesting.

Jim

[Jerry V Lape]

And the point that James just made was why it fades out as there I no appreciable advantage derived from going the trouble of making the polygonal rifling.  There was also rifling done in England with a bore which was a little oblong in cross section with an appropriate twist to the oblong feature.  It too has faded into historical oddities which worked but weren't worth the effort with barrel and with the specialized projectiles. That may be the invisible rifling Daryl referenced. 

[WadePatton]

Hi Guys,  I have a question regarding polygonal rifling on a muzzle loading rifle. Has it ever been tried and what were the results. Seem like a good compromise between a smooth bore and a rifled barrel. Easy to clean and load and still accurate. Forgive me if this seems a stupid question but this type of rifling has worked very well in cartridge guns. Thanks for any response.

What you may not fully comprehend yet is that any twist imparted by the bore is bad for shot loads.  The centrifugal forces scatter the shot such that you'd yet have a rifle without lands and grooves. It would not be like a "smoothie" because shot loads would be irrelevant.

and what the other fellows said.

Also, rifles are easy to clean and load.  I think there's a thread on it. 

[Bob Roller]

And the point that James just made was why it fades out as there I no appreciable advantage derived from going the trouble of making the polygonal rifling.  There was also rifling done in England with a bore which was a little oblong in cross section with an appropriate twist to the oblong feature.  It too has faded into historical oddities which worked but weren't worth the effort with barrel and with the specialized projectiles. That may be the invisible rifling Daryl referenced.

Lancaster oval bore.It came along at the time of Alex Henry,John Rigby and others like the two
groove Brunswick.

Bob Roller

[ron w]

if it were good, it would have survived. I would think that like the Whitworth, unless the rifling is distinctly hexagonal and the projectile close fittl and similarly hexagonal in section, there would exist a very large potential for the round to skip rotation from the rifling being also cushioned by a patch.

[Hungry Horse]

The hex bullet in a whitworth torqued against the close fitting hex bore of the barrel, with no chance of "stripping" as a regular bullet in a traditionally rifled barrel would have, with such massive charges. The wear was substantial enough that some Confederate examples captured near the end of the war were no longer using the polygonal bullets, but had gone to a traditional bullet, finding that they gave a reasonable degree of accuracy, where the polygonal ones did not.

  Hungry Horse

[Daryl]

There is a difference, at least today, between the hexagonal rifling of the Whitwhorth and what the Euros and Pac-Nor are turning out as POLYgonal rilfing.

Even Wikipedia has it right.  The key words are: rounded, hills and valleys.

https://www.google.ca/search?q=Polygonal+Rifling&ie=utf-8&oe=utf-8&gws_rd=cr&ei=-HbNWNvFO4jPjwSLv7zoBQ

In cross section, the picture on the right, compared to normal on the left, is the type of polygonal rifling I was referring to.



Further- I can see it working WELL, with jacketed bullets only, not so well with lead or patched, unless the twist was VERY slow -ie: 90 to 120inch.