Greetings All,
There appears to be some misconceptions about correct rifling twist being discussed here.
But first Justin, you are going to have to decide if you want to shoot conicals or round ball most of the time. Each bullet/ball type requires a different type of rifling.
Patched round balls in 50 caliber or above give best accuracy with slow twist like 1-60 or slower. BUT only if the grooves are not less than 0.010" deep and are at least equal width to the lands. Wider grooves are not harmful and usually can take a tighter ball/patch combination.
The slower the twist, the higher the velocity needs to be to obtain the best accuracy past 50 yards. This means heavier powder charges and more recoil.
The reverse is also true to a point. Historical research reveals that the 1-48 twist was a standard among most BUT NOT ALL old time gunsmith and was still the most popular twist until the mid 1950,s or so. Around that time the 1-66 began gaining in popularity and evenually became the new standard. As a rule, best groove depth is 0.010-011". 0.012" and deeper seems to break over into the point where too thick a patch is needed and accuracy suffers. Most original Hawken rifle barrels had a 1-48 twist. Interestly enough, a few very late Hawkens manufactured by Sam Hawkens successor, J.P. Gemmer have quick twist rifling that would accomadate only a conical projectile. Evidently, Mr. Gemmer recognized the advantages of a heavy conical for the bigger game of the American West.
The truth be known, I'd bet that more Western big game was killed with the Post Civil War rifled-musket and minie ball, than all of the pre-war round ball guns put together. One of my friends swears by his Civil War replica Enfield and conical for our Texas deer and wild hogs. He seldon uses a round ball rifle anymore.
A 1-48 twist with 010-011" deep grooves will shoot round balls very accurately. In fact, match winning accuracy, but is somewhat more temperamental in regards to varying velocity ranges which interprets to powder charges. The 1-48 handles(in 50-58 caliber) 50-65 grain charges of 2ff or 3ff with out standing, match winning accuracy. 80-85 grains of 2ff or the equivalent load of 3fff seems to be the limit for best accuracy. Velocities faster than this seem to cause the ball to jump over the rifling.
Currently the only way to rifle this deep is to use the cut rifling method such as used by custom ML barrel makers or operations like GREEN MOUNTAIN.
The Lyman GP rifle with a 1-66 twist has the deeper rifling that promotes great round accuracy. Rifling depth in the other models with the 1-48 or quicker twist is more shallow and designed for conicals. The button rifling method is a less expensive mass manufacturing process, but also induces horrendous internal stresses in the barrel and is limited to shallow groove rifling. Custom centerfire barrel makers who use this process stress anneal twice during the manufacturing procedure.
I have long suspected that some the wildly inaccurate black powder rifles are due to stressed button rifled barrels.
Good, sometimes great accuracy can be obtained with a shallow groove button rifled 1-48 barrel, but generally in the 50-60 grain powder range generating lower velocities. High velocity loads will definately "jump" the rifling. The patch and ball diameter is also a critical factor in a shallow groove barrel as well as patch lube and how it is used.
With calibers of 45 and smaller, the 1-48 works much better. In fact, a number of barrel makers do not offer a faster twist for 45 caliber and smaller. In reality, who needs high velocity in a 32-36 caliber bunny or squirrel rifle? Anybody have any idea how many bunnies and squirrels have been shot with the 22 long rifle cartridge? Me either, but none of us have the time to count that high: at not at my age.
Anyway, back to the subject. The shallow groove, fast twist rifling pitces are designed for conicals, but all conicals are not equal.
It is not enough to find a conical that has a proper fit in the bore, but length is also important, not weight. Weight is important only in relation to length. Heavier bullets are generally longer. As a rule, longer bullets require a qicker rifling twist, while short bullet(lighter weight) need the slower twist. The old GREENHILL FORMULA was developed for lead conicals/blackpowder combinations and is still valid today for that combination.
For hunting purposes, conical point shape is also important. Sharp pointed designs have a tendency to punch a hole in deer size animals without expanding unless a bone is hit. A more blunted, slightly hollow pointed design seems to be a better big game design.
Having said all of this now and put myself out on a long limb, I acknowledge that exceptions to all of the above exist, and for these I have no explanation.
Hopefully, this desertation will be useful to newer shooters in this game and clear away some of the fog surrounding blackpowder rifling twist. Much more can be and has been written on the subject; my posting only hits the high points.
Best regards, John L. Hinnant
