Rice Barrels makes the polygon Alex Henry for the Rod English/Don Brown Alex Henry
long range.They are 7 wide grooves and narrow inverted lands.This system surpassed
the hex Whitworth and is VERY useable with common cylindrical bullets paper patched
or grooved.
Bob Roller
I will check it out, thanks.
I am not convinced the original Whitworth polygon is the cat's meow. The 21 inch twist might be it. I will run Postells through the Sharps with 18 inch twist for some trials. I have sizer dies in .456, .457 and .458. One should work out.
18" will work better with long bullets in 45, the last LR bp/lead bullet guns in the US used 18 twist. Remember when the gov't adopted the 22" the 405 gr bullet. The longer bullet was an after thought.
Also Greenhill's formula is always about 2" slower than it what works best being intended to calculate twist rates for ML artillery.
I and a "rifle crank" friend once (back about 40 years) had a barrel cut by Ron Long that was rifled with a .456" or .457" BORE. It allowed a Lyman 457125 to be started with the fingers with none of the coning fad. The bullet design does not suffer from having the nose slump off center so a soft alloy could be used. Recovered bullets would show bore riding nose was really riding the bore all the way to the ogive. It shot pretty good for our knowledge level of the time. Needed a platinum lined nipple even with 70 gr of powder. IF I were going to make a LR ML I would set it up with a false muzzle with a guide starter and shoot PP bullets. No leading and the bullet is more aerodynamic for LR shooting. I would likely play around with swage making too. Though somewhere in the shop there is a 40 and a 45 swage already that work pretty good.
The twist rate much over 18 in a 45 cal bullet gun is a mistake IMO. Cast bullets ALWAYS have flaws, the greater the RPM the greater the chance there will be a flaw that will cause a flier. Greater than a slower but adequate twist would produce. I know a guy (that rifle crank) who played with this. This is why the old time slug gun shooters, the precision bench rest shooters of their day, used swaged bullets from before the US Civil War. They also used false muzzles on the guns with a guide starter. The false muzzle was crowned or relieved so that the muzzle of the barrel was left perfect. They often used a "cross" paper patch. Some used two piece bullets with a harder streamlined nose to prevent slumping under initial acceleration, the two pieces were then swaged together. Swaging cast bullets reduces the size or any flaws in the bullet. Also if you are REALLY serious you need to find a barrel maker that is expert in precision barrels, like Krieger or maybe Bartlein barrels or one of the others and ask about coning.
And finally the LR percussion rifles the Whitworth and Rigbys etc were designed for quasi military rifle competitions. All comments to the contrary not withstanding they were not the high precision rifles of their day being rules limited in weight and used unsupported in matches.
In context of this website...
Elongated bullets in MLs are problematic for any use other than military tactics of the 19th c or competition on a range. For hunting they are prone to slide away from the powder charge. This was a problem with the military as well (the Minie Ball and variants if not thee then the close to the most useless projectile for civilian purposes (the military never did make it work for the cavalry) ever invented, the original "Maxi-Ball" is not far behind). While the cloth patched "Picket" or "Sugar Loaf" bullets would no move off the powder they still needed a guide starter to obtain usable accuracy. Without the starter, precisely fitted to the barrel and the ram carefully fitted to the bullet nose accuracy is "problematic". The one I made for my 40 cal experiment weights about a pound and they are easily damaged. No matter what one might think from reading Ned Roberts. The the average person staid with the round ball for the ML rifle. And not just because of the extra gear needed to shoot elongated bullets. If we read Greener, Baker "A Hunters Wanderings in Africa" and especially Forsythe "The Sporting Rifle and It's Projectiles" we will see that there were and are killing power issues that favored the RB.
