Barrel Twists

[Buck Snort]

color=blue][/color]I was really happy when I stumbled on to this form. I have shot front end loaders since I was a teen. I never was shown anything about them and learned as I went. I've put together quite a few shooters, always trying to build a really good one. Some were and some needed to go back to be reworked. Great fun. I watched a show on the Outdoor channel about some fellow shooting in some competition, with a muzzleloader. He was shooting 500 yards and had like 45 minutes to complete so many rounds. I was totally intreeged. He shot a 400 - 500- grain slug ahead of 80 grains of powder and was hitting an 18 inch steel. Wow. Traditional style gun with a few newer looks to it. Basic side hammer and longer barrel, with a set trigger and target type open sights. I so want to do a build like that gun. My question to you guys that know what is going on, is, to shoot a large bullet in say a 45 cal., what twist would be the optimum and what length barrel would you shoot? I have read so much about Knight and their problems with the wrong twist and others as well, when shooting the slugs. I know from experience that the old kits that had 1 in 48 or something like that, would not shoot anything but balls. I am confused about the matter.

 

[bwhoffman]

My guess from looking into BPCR and such would be to have a twist of at least 1:16 if not even closer to 1:12 or 14 and probably at least 32 to 36 inches long.
Not an expert by any means, just remember when I too was enthralled with shooting outwards to 1000yds!

 

[paulab]

Hi Buck....If you are going to shoot long range with a m/l [up to 1000 yds.] You need a 30 to 34 inch barrel in .45 caliber with a 1:18 twist. Your bullets will either be grease grooved or paper patched up to bore diameter and weigh around 500-530 grains. Be advised that to take FULL advantage of your rifle's capabilities you will need to invest another $500 in a windage adjustable tang sight and spirit level windage adjustable globe front sight. Standard barrel sights just won't do for long range work. Check out the Pedersoli Gibbs long range M/L. It comes with all the bells and whistles right out of the box. Cheers Paul

 

[Idaho Ron]

Here is a TC Renegade with a 1-18 twist .458 diameter Green mountain barrel. It has a Lyman 57 SML peep sight and a Lee Shavers globe with a level on the front sight. This rifle would shoot out to 500 yards but so far the farthest I have shot it was 300 yards. Ron

 

[Billnpatti]

You can calculate the optimum twist rate using the Greenhill Equation. You can find it by Googling "Greenhill Equation" or you can find it in a book entitled "Understanding Firearm Ballistics" by Robert A. Rinker. It is on page 141 in my copy.

The equation is: (C x diameter of bullet squared)all divided by the length of the bullet. "C" is a constant based on the muzzle velocity of the bullet. If the velocity is below 1800 fps, C=150. For muzzle velocities greater than 1800 fps C=180.

Here's an example: Lets assume that you are shooting a .45 cal bullet that measures 1.1 inches in length at 1600 fps. "C" would equal 150 because your M.V. is below 1800 fps. That would give us (150 x (.45 x .45))/1.1= 27.6. So, the optimum twist rate to stabilize that particular bullet at that velocity, you would need a twist rate of 1:28 inches.

You might also find the Davenport Formula useful. It assumes an maximum efficient load of 11.5 grains per cubic inch of bore volume. It is not an exact number because it doesn't take into account the various brands of powder nor the various granulations but it is a good start. The formula is Pi X the radius of the bore squared X the length of the bore X 11.5.

Here's an example of the Davenport formula: Lets assume a .45 caliber barrel that is 34 inches long. The radius of a .45 barrel is .45/2 = .225. The square of .225 is 0.0506 So we multiply 3.1416 X .0506 X 34 X 11.5 = 62.155. Therefore the approximate maximum efficient load for this rifle would be 62 grains. This will vary considerably depending on your particular powder but it a good starting point. If you load more than the maximum efficient load, you are wasting powder because the excess will just be blown unburned out the muzzle.

If your local library does not have a copy of Rinker's book on the shelves, they can get one for you through interlibrary loan. It's a dandy book to have in your library so you may want to buy a copy. While it sounds rather technical, it is written for the average person.

I hope this has helped you. :thumbsup:

 

[dyemaker]

I had found this book earlier that relates to your topic. It was written in 1864 and contains some details about some of the 1860's volunteer and long range competition rifles and shooting them.

Notes on rifle-shooting By Henry William Heaton

book

 

[Buck Snort]

WOW you guys know your stuff. One of my projects was a 45-70 barrel I had laying around. It had a 1-18 twist barrel bt was only 20 inches in length. I built an inline with it and it shot saboted lead slugs, beautifully. That got me thinking anout the Knight rifles as to why they were said to not shoot slugs well, with the 1-20 twist. I'm going to take the information you guys gave me and start a plan for my build. I may not shoot competition but I would like to slip a big slug into a big boy with horns, out to 200-250 yds. Thank you guys

 

[ron ward]

the greenhill formula will give a close idea of the twist needed.... be aware that it was developed for big bore cannons and has been identified as only a good ball park equation for bores as small as 1/2 inch. lots of discussion about it's usefulness with small bores on the "accurate reloading forum", just search "greenhill". the formula's constants are more dedicated to bullet length than weight at different densities (different materials used for cannons) and diameters well above the bore diameters of small arms and will generally result in a twist that is just slightly too slow for the bore/bullet length of our guns. it is all explained clearly on the AR site.

 

[pchwcf50110]

most english .451-.461" target rifles were 1-18" to 1-22" with 1-20" being the most popular. there were some slower twists 1-30" but as the discipline of long range shooting was established most makers used 1-20". powder charges were 85-90 grs. bullet weights ran from 480-530gr. and kind of settled on 530gr.

 

[zrifleman]

Cabelas has the Pedersoli Gibbs on sale and it is a bargain at regular price. You get a really accurate rifle ready to go right out of the box. You will be hard pressed to build one that even comes close to it for the same money. If you insist on building one Track Of The Wolf sells a Rigby kit, so does Pecatonica River.

 

[dyemaker]

To remind you, another option if you are interested in buying a good used Volunteer replica would be to try to find a Rigby rifled 2 band Volunteer rifle made by Parker Hale in the 1970's or whenever. You might be able to find a good one if you are lucky. They made Alex Henry rifled 2 band Volunteer rifles later on too. Unfortunately Parker Hale is no longer in business. I know they were still making barrels up until a couple years ago or so. It's too bad because the rifles were nicely made replicas.

Otherwise make sure to post pictures if you build one!