- January 17, 2017 at 4:51 pm #32784GoodsteelKeymaster
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Ruminations, ponderings and observations of 40 years of muzzleloading barrel making.
Lesson one: choke and how it relates to the muzzleloading barrel..!!!
Well men, it appears my old buddy Frank House has prodded me into discussing the more scientific side to shooting a flintlock or percussion rifle. More so, what exactly occurs when the blackpowder rifle is fired. At least as far as internal bore dynamics are concerned, and how the 18th century barrelsmith and myself deal with this form of percieved alchemy. ..lol…!!! Better yet, how we try to dictate what the patch, ball and powder will do..!!
Now everyone knows that a barrel is merely an octagon, octagon to round, round or some other variant there of. Which is either rifled or smooth…right?? End of story…correct..? Well….not so fast guys…there is a bit more going on than meet the eye here.Bore geometry definately comes into play here, and in a recent conversation with Frank House we got to discussing some of the finer nuances of barrelmaking and their effect on accuracy.
First off, wheather the barrel is of modern steel manufacture or hammered from a glowing orange “skelp” of iron, matters not. Once a uniform bore dimension is established in either one by means of a drill of one sort or another, the barrel is ready to ream. Or bring it to its finished bore dimension. Or say .500″ in a .50 calibre, or wherever the 18th century gunsmith deemed it to be sufficiently uniform and smooth….albeit maybe 47 1/2 cal..??
Now…technology of yesteryear dictated that one would use a 6″-7″ rectangular hardened “square reamer”, backed with a piece of hardwood and then drawn though the barrel while an apprentice spun the barrel in his period reaming machine. They went until said hardwood wedge no longer held up and then a new wedge was added to the reamer until it gave up the ghost….and so on and so on. Until the muzzle was reached. Its important to note that it MUST be done from BREECH TO MUZZLE. This was effectively cutting a choke or taper in the bore….usually too much taper. So the gunsmith would have to go back and remove all but about .002″ . What does choke do..??? I’ll get to that. I do the same thing through modern alchemy….employing a pair of 10 flute reamers…done back to back and ground very uniquely to give me the same desired effect. Once again, Ill explain why shortly. Now that the barrrel has a very uniform and smooth surface….it is ready to rifle.
Once again, this procedure is done breech to muzzle…..Everytime. Where as I use a modern steel rifling rod and head with carbide cutters and flooded with oil, the period gunsmith employed a steel rod with either an iron or hardwood rifling head. It utilized a scraper type cutter that was lubricared with oil and fine paper or wood shavings to regulate depth of cut.. it again was drawn through the barrel by the apprentice. Again…as the wood shim wore as it shaved off the iron grooves, additional shims need to be added to finish the cut end to end…..once again creating a taper to the rifling from breech to muzzle. I utilize a specual rifling head to perform the same task…tapered rifling from back to front.!!!!! These two dynamics are the secret to an accurate barrel..!!!! Why..?
For years people used to say to my father and I…”there’s a tight spot in my barrel 5″ down from the muzzle”! And I would jokingly say. “No, there’s technically a loose spot behind it..!”. Anyway…..what could that choke possibly do to help accuracy..?? After all, that patched round ball only remembers the last inch of rifling….right..?? Well fellas….it dosent really affect the ball persay. BUT it dictates A LOT what that powdercharge does..!! By providing more resistance to the patched roundball …which “upsets” at detonation then grows tighter and tighter as it approaches the muzzle. This creates much higher pressures within the bore which creates a much better burn enviornment for more complete and UNIFORM combustion. Which translates into uniform velocity. AKA ….ACCURACY..!!! In BOTH rifled and smoothbore configurations. Get it..??? Famed barrel maker Harry Pope of the 1870-1880s utilized gain twists to provide the same resistance in the balckpowder cartridge realm. The same net as “choking”….. both the tapered rifling and bore constriction make a lethal combo. Wheather they knew it was an accurate system or it just worked out that way is anyones guess…but it certainly made an impression on the British during its Colonial War. Okay guys…my thumb is aching. Hope you guys enjoy my ramblings.
- January 17, 2017 at 5:01 pm #32786Rattlesnake CharlieParticipant
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Thanks for the article. Very interesting theory.
I had read that a ML with a choked barrel was supposed to be more accurate. When I made the barrel for my ML pistol from the shaker shaft of a Massey-Harris combine I wound up with one end being a larger bore than the other. On accident. I don’t know how it happened since I bored it on a 20th century lathe. I did make the tight end the muzzle.
- January 17, 2017 at 5:22 pm #32787GoodsteelKeymaster
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I’ve been thinking about choked barrels here lately. I keep wondering how to get around the bullet getting sized down by the lube in high velocity smokeless shooting. Ordinarily, I would say barrel quality played a much bigger role in accuracy than rifling form or choke, but if our bullets are getting smaller as they proceed to the muzzle, it does make me wonder what would happen if the barrel chased the bullet a little bit. It certainly would not eliminate the problem, but it might give us an edge, and as I’ve domonstrated time and again, sometimes all you need is a slight edge in the right direction to make interesting things happen!
Regardless, this was written for BP context, and I agree with what is said so this is where I put it.
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