View Full Version : Twist Rate references?

May 21, 2008, 10:08 PM
Anyone have information on a collection of factory rifling twist rates for major firearm manufacturers?

I'm working on a project and am trying to save myself the effort of 're-inventing the wheel' in this regard. I suppose if I must, I'll have to start writing to various manufacturers.

Anyone know of any websites or books?


James K
May 22, 2008, 11:46 AM
Each manufacturer uses several twist rates, based on the cartridge the barrel is made to fire. For example, Remington uses nine different twists in the Model 700, depending on caliber. Further, some makers have changed twist when a different bullet weight became popular in a given caliber.

Even so, those twist rates are compromises to some extent. The "ideal" twist rate depends not only on caliber, but on velocity, bullet bearing area, bullet sectional density, etc.


Jim Watson
May 22, 2008, 01:24 PM
Most makers have their twist rates listed by caliber in their catalogs and their websites.

I guess I could look them up for you. What is your budget for consulting engineers?

May 23, 2008, 10:14 AM
I've been doing the searching on websites. Ruger is the only website I've found with the information provided. I will continue to look but I was hoping someone - in their extensive readings and mental travels - might have seen a reference work or site that has already compiled the information. (Usually I find such things AFTER I've painfully dug up what I wanted...)

I fear my budget for consulting engineers, or consulting researchers, is rather limited. Thank you ever so much for your kind offer.

Mr. Keenan, I'm aware of the Greenhill formula and such. What I'm seeking is the actual twist rates used in specific models of firearms. The point of this project is forensic identification.

I'm putting together a different research project into 'updating' the Greenhill formula, seeing if ballistic coefficient has a bearing on ideal twist rate - but 'ideal twist rate' is a whole different matter than historical or reference information.

I never knew firearms research could be so - tedious.

Thank you both for the replies. I appreciate your time.

Jim Watson
May 23, 2008, 10:38 AM
OK, here's a freebie:

Remington, from their website:

17 Remington Fireball 9"
204 Ruger 12"
22-250 Remington 14"
223 Remington 12"*
308 Win 12"

243 Win 9 1/8"
270 Win 10"
7mm Rem Mag 9 1/4"
30-06 10"
300 Rem Ultra Mag 10"

*They have tackytickle models in .223 with 9" twist.

James K
May 23, 2008, 05:54 PM
The information on the 700 Remington is from a book called "The Remington 700, 25 Years" by John Lacy.

Here are the ones in the book:

.222 Rem, .222 Rem Mag, .22-250, and 458 Win Mag - 1 in 14" twist.

.250 Savage, .257 Roberts, .25-06, .270, .308, .30-06, .300 H&H, 8mm Rem Mag, and .338 Win Mag - 1 in 10" twist.

.223 Rem, .375 H&H - 1 in 12" twist.

.243, 6mm Rem - 1 in 9 1/8" twist.

7mm-08, 7mm Mauser, 280 Rem, 7mm Rem Mag - 1 in 9 1/4" twist.

.308 Win, Varming Special - 1 in 12" twist.

.350 Rem Mag - 1 in 16" twist.

I am not sure why you want to update Greenhill, except maybe for something like the .17 caliber, which IIRC Greenhill doesn't cover. To do so would require a lot of both computer work and actual experimentation. The Greenhill formula will produce an ideal twist rate. But firearms engineers don't work in an ideal world. They have to produce a rifle in, say, .30-'06, that will be reasonably accurate with bullets from 110 grain to 220 grain, plus the Remington Accelerator. They know all about the Greenhill formula and have some of the best ballistic software in the world, but still have to compromise. The alternative would be to tell the buyer of a Remington 700 in .30-'06 that he can use only one specific bullet if he wants accuracy, an approach not likely to make many friends for the gun company.

For forensic purposes, police firearms examiners (misnamed "ballistics experts") have access to data provided by the factories. For obsolete guns, especially handguns, they have Matthews and other reference books. I am much afraid you would be re-inventing the wheel in that area, but have fun.


May 23, 2008, 10:24 PM
Thanks for the information. I suppose I'll have to buy that book for my library. Trying to be the smartest guy in the world is an expensive undertaking. :)

Updating Greenhill is more of an intellectual exercise. You are right of course in that the manufacturers figure on the whole range of 'likely' bullet lengths to be used and twist things accordingly. It's not like one 'sets' the spin for a specific bullet one fancies this week.

I just have an inquiring sort of mind about such things. Besides, one discovers very interesting things when researching theoretical abstractions.

As for the forensics abstract, I've read too many 'insider' memos and reports with some amazing gaps in the data about 'bullets'. :eek: Just trust me on this.

Mr. Watson, I appreciate your input as well. Back to 'digging'.