twist ????

[trapperdan2061]

I have done some research and am finding that a 1 in 70 twist is the best for a patched round ball, have you also found this to be true?

Thanks

 

[David W.]

I have done some research and am finding that a 1 in 70 twist is the best for a patched round ball, have you also found this to be true?

Thanks

Welcome to the forum!

It depends on the caliber. .32 to .45 the twist should be around 1:48, .50 thru 54 1:56, .56 .62 1:66.

 

[nkbj]

Just to give an idea of the way it calcs out with the twist formulas on the interseine, here's the results for projectiles that are one caliber in length:
32 cal = 1:48"
40 cal = 1:60"
45 cal = 1:67"
50 cal = 1:75"
54 cal = 1:81"
58 cal = 1:87"
Those are ballpark, they're approximate and change around a little bit with whose calculator you use and whatever you input.

 

[paulvallandigham]

It really depends on the caliber of the gun, and the amount of powder you want to use. A PRB will fire accurately out of any ROT, including very fast, " Pistol " ROTS that are 1:20 or less. But, the velocities at which a PRB is accurate when turned faster, are reduced. The Slow rate of twist tends to be more forgiving to changes in powder charges, than faster ROTS. That is why RB guns tend to use the Slower ROTS.

Shooters like to measure their powder in the filed by simply using a cup like powder measure to determine the powder charge by VOLUME! NO one measures their powder charge by actual WEIGHT. With volume measures, there can be variations in the actual amount of powder thrown, and the slower ROT allows the ball to shoot to the same POI down range, even with a variation as wide as 5 grains of powder( by weight). With faster ROTS, a variation of the actual weight of the charge by that much may send the ball to a different POI.

Finally, some shooters claim that the slower ROT results in less recoil. My personal experience is that I don't notice any difference shooting RBs, but a faster ROT can increase the felt recoil shooting conicals. You generally will need a faster ROT to shoot conicals accurately. :surrender: :thumbsup:

 

[Tom Compton]

PRBs tend to shoot more accurately w/ deeper grooves (.100 -.015) and tight ball and patch combinations (like .495 ball and .012 patch).

 

[Dphar]

I have done some research and am finding that a 1 in 70 twist is the best for a patched round ball, have you also found this to be true?

Thanks

The round ball does not seem to care a great deal what the twist is. Douglas used 66 for everything.
Some like 48 some like 72 depending on caliber. Bill Large made a lot of 56 twist barrels.
I would prefer a 48 over a 70 in a 50 caliber but not sure there is any real difference.
Some say the 48 is more finicky than a slower twist. I would suggest then look at John Baird's "Hawken Rifles the Mountain Mans Choice" for a description of a test of a 48" twist barrel.

Dan

 

[BrownBear]

There's some really useful info on twists scattered through this thread.

In my own use of different twist rates and calibers, I think there's a whole lot more keyboard ballistics than fact in the topic.

 

[longcruise]

formulas on the interseine,

I'm stumped. What the heck is the "interseine"?

 

[necchi]

net=seine, some time ya gotta 'fish" for the right info, :haha:
the internet can be insane? :wink:

 

[David W.]

Just to give an idea of the way it calcs out with the twist formulas on the interseine, here's the results for projectiles that are one caliber in length:
32 cal = 1:48"
40 cal = 1:60"
45 cal = 1:67"
50 cal = 1:75"
54 cal = 1:81"
58 cal = 1:87"
Those are ballpark, they're approximate and change around a little bit with whose calculator you use and whatever you input.

I am not too sure about this calculation chart, maybe it has some merit.

All I know is that my .62 rifle is with a 1:66 twist made by H&H (Hoppie Hopkins) who was the top barrel maker of that time. I also have an H&H .36 with a 1:48 ROT. If a top barrel maker chose that twist, I figure he knew what he was doing. I understand the company is owned now by DeHass and produces the same high quality barrels. I have absolutely no complaints with acheiving top accuracy, except for my aging eyes.

 

[Walks with fire]

Don't forget barrel length affects how much powder can be consumed so carbine length barrels can have faster twists because the velocity is lower. The trick to the carbine lengths which are so handy is to to match the twist, caliber and 3f powders so you can get the power in a handy and light firearm. I have a 24" 1:28 twist 50 caliber flinter that shoots balls,bullets and conicals outstanding with 3f powders. I like the faster twists better in short barrels.

If I were to have a 42" barrel in 50 cal. for a ball gun then I would probably want something in the 1:60 twist range for good accuracy with up to 110 grains for short ball-ets and roundball. My primary use is deer hunting with little target shooting.

 

[bkovire]

get the twist you think is the best, if you shoot only rb then 1 in 70 is ok if you are to shoot mines or them other type of lead then get 1 in 48 or faster, back when flint was the only one, 1in 48 and one half was the common twist, and the length 48 in long, some were as fast as 36, slow as 80+ something, i was reading on this last night. if i knew how to post the link i would.

 

[nkbj]

The only merit those figures have is just to show the purely theoretical twist needed to stabilize projectiles that are one caliber in length.

 

[rmark]

http://en.wikipedia.org/wiki/Rifling

scroll down to the discussion on the Greenhill and Miller formulas.

 

[nkbj]

I've kind of copped the attitude that rifling spin is like going to Mardi Gras: If you don't have excess you don't have enough.
The various formulas are pretty good for figuring out the general danger zone of not having enough. Some have inputs for ogive and base types. Somebody may even have a really sophisticated one that includes grease grooves.
I think that for bp the ol' Greenhill is all you need to get you in the ballpark. After that it's still a matter of if something shoots then by golly it do.

 

[longcruise]

net=seine, some time ya gotta 'fish" for the right info,
the internet can be insane?

Hah! Now I get it.

When Dan said;

The round ball does not seem to care a great deal what the twist is.

He hit the nail right on the head. Typical calibers used by many shooters today .45, .50 and .54 will shoot well with twists ranging from 1:48 up to 1:70 and probably much slower twists to boot. As long as it is not spun too terribly fast at too high a velocity, it will tend to shoot pretty well. There is no definitive point for a round ball where there is not enough twist and the ball simply flys haywire. A smoothbore with no twist can shoot pretty well and a rifle with a 1:200 twist would probably shoot good too.

The greenhill formula can be used with varying constants from 120 up to 180 to arrive at fairly accurate estimates of twist rates needed for bullets. As velocity goes up, the constant number needs to go up somewhat. I'm not capable of doing the math to determine the correct constant for any one caliber/length/velocity, but one thing is for certain; when a bullet is inadequately spun it is going to fly sideways within 25 to 50 yards and will usually impact many inches or even feet from point of aim. In addition, the elongated bullet undergoes a traumatic experience when it goes sub-sonic. Even the short for caliber military .30 cal 150 grain fmj for some reasons tumbles when it decelerates below the speed of sound. As far as I can tell, this destabilization does not happen with the round ball as it goes sub-sonic.

Even though a ball from a smoothbore tends to drift about a bit it is still in the realm of useful up to it's range limitations.

 

[paulvallandigham]

As a general rule, you can use the Greenhill constant of 150 for calibers that will fire a bullet at 1500 fps. or less. If you are shooting faster than that, increase the constant to 180.

Its also common to reduce the constant from 150 down to 120, or even lower when attempting to use the formula for short barrel rifles, and pistols.

Because BP rifles usually do not attempt to fire lead bullets at velocities greater than 1800 fps( yes, I know some guns where velocities are over 2,000 fps) normally that is as much of an adjustment to the constant that you have to make( 180 for 1800 fps and above.) If you have a small caliber rifle that will push a bullet at over 2,000 fps., go ahead and change the constant to 200 and try the formula to see what you get.

Understand that these formulas indicate the SLOWEST ROT that will stabilize these bullets( balls) at the velocity ranges indicated. You can always use a faster ROT in a rifle to improve performance. ( ie, if the formula says use no slower than a 1:72" ROT, you can shoot quite well with a barrel with a 1:60, or 1:66", and even a 1:48 or 1:56" ROT.) Whether a gun will shoot Conical bullets well is largely determined by the depth of rifling- not just the ROT. :hmm: :thumbsup:

 

[nkbj]

For conicals, more so design of the projectile, the manner of loading and the twist and style of rifling than the depth. If the twist is fast enough a tinkerer can generally make it work.

Came by a TC .50 barrel in a 1:48" twist that my "new" paper patched mould firmly fits with 25% rag onion skin. The TC has equal width grooves and lands. The Green Mountain LRH (1:28" twist) has small lands and larger grooves. It's going be instructive to see how the TC barrel compares to the GM.

 

[David W.]

I have done some research and am finding that a 1 in 70 twist is the best for a patched round ball, have you also found this to be true?

Thanks

I told you that you would get many different answers. Getting advise on conicals when you are asking about PRB's, extremely wide variations on twist. 1:28, 1:48, 1:66, 1:87, 1:200. No, I'm right, no, you are wrong and I am right. The fact of the matter is, that rifling IS set by the diameter of the bore and is a general guideline. It is also why you do not see barrels offered in every concevable twist imaginable.

Most of the people manufacturing barrels are not idiots. If you go to Green Mountian or Colerain, you will see twist the rates are close relitive to caliber and to each other. This is because they are not set up for a particular powder charge and attempt acheive to select a twist rate that is suitable over a wider powder charge range.

With all the formula's that you have seen for exactness, you would have to the rifling custom made. I would just go with one of the barrel makers such as GM, Rice, Colerain, DeHass and be done with it. Or you can spend big bucks and tell a custom maker what caliber you want, what powder charge you wish, what velocity you need, and what range you will be shooting, and open your pocket book.

There is no exact answer to this unless you are going to be competing for the world wide target trophy. Are you throughly confused by now with all the different answers? So am I! :hmm: :bow:

 

[paulvallandigham]

Everything you say is true, GoodCheer. However, so few people are " tinkers" who come to this sport that your expectations are far above the real skills of most shooters.

My comment was based on what I know about BP shooters, and how easily frustrated they get when the gun they want to shoot can't hit the side of a barn. They tend not to be Internet guys, like us, and, sadly, they have not heard of this forum. They don't belong to BP clubs, much less the NMLRA, and they have NO one to ask questions for guidance.

I also suspect that less than 5% of All Shooters even know what a Paper Patched bullet IS, much less how to do it. [BTW, I understand that there is a new book out explaining how to PP bullets.] Learning how to seal the bore of a rifle designed to shoot PRB, so that it will shoot a lead bullet accurately is a HUGE step for most shooters to take.

Learning how to shoot a PRB out of a barrel rifled to shoot conicals is quite a different adventure, but a day trip compared to the longer trip needed to be proficient shooting PP bullets out of a RB gun, IMHO.

I credit IdahoRon, a member here, for sharing much information with the rest of us about paper patching bullets in MLers. My only experience with PP bullets has been with BP cartridge rifles, but those rifles are rifled with shallow grooves, and have the correct ROT to shoot conicals, and bare lead bullets. They do not have deep grooves, or slow ROT rifling that you find in the average traditional, RB Mler.

In fact, I have been working with "squib " loads to find accurate RB loads to use in my BP cartridge rifles- the opposite of working up powerful, PP bullet loads in those guns. :youcrazy: :shocked2: :rotf: :surrender: :thumbsup: