Please Explain Twist Rates

RangerEd · #1 03-06-2010, 10:22 PM

Could someone please give me a better understanding of twist rates. I have seen (If I recall correctly) opposing information. Trying to understand this, I have read where one wants higher twist rates on heavier bullets and then just the opposite. Does it differ from caliber to caliber, load to load, situation to situation?

Thanks,
Ed

NomadPilot · #2 03-06-2010, 11:07 PM

All else being equal, heavier/longer bullets need faster twists.

GunTech : Calibers and Twists - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools

MontanaRifleman · #3 03-09-2010, 10:08 AM

It has a lot more to do with the length of the bullet than the weight of the bullet. Longer bullets require tighter twists than shorter ones to stabilize.

Chas1 · #4 03-09-2010, 10:47 AM

Ditto w/others. Here are a couple of links that may be of interest:

GS CUSTOM BULLETS - Twist Rates and Bullet Length

GS CUSTOM BULLETS - Bore, Groove and Twist Specs

long range erik · #5 07-05-2010, 05:33 AM

Im confused, if faster twist rate mean you can fire heavy and light bullet, why don't all barrels have a fast twist rate. Is this because it is harder or more expensive to produce or is it because slower twist rates are more accurate for certain bullets ect.

groper · #6 07-05-2010, 05:58 AM

Quote:

Originally Posted by long range erik

Im confused, if faster twist rate mean you can fire heavy and light bullet, why don't all barrels have a fast twist rate. Is this because it is harder or more expensive to produce or is it because slower twist rates are more accurate for certain bullets ect.

Its because every bullet has an 'ideal' twist rate that works best for that individual bullet based on its length, velocity and weight etc. Gun makers can only barrel a rifle with a twist rate that they think will be the best compromise for all the bullets likely to be popular with that particular rifle they are bringing to market.

much like a car has features within a given model based on which market that model is likely to be sold to. its not perfect for everyone, but rather works for most people in most instances, in order to be appealing to the majority, to sell as many as possible...

different rifles have differnet purposes, and there are different bullets for many calibers... some are suited for long range, some are suited to short range, off hip hunting, some are suited to varminting, some for big game, the list goes on... one twist rate will not be ideal for everything, so people and gun makers try to best match a barrel twist rate based on its intended purpose (and therefore bullet type) for that type of gun.

johnnyk · #7 07-05-2010, 09:49 AM

Ed,
Twist rates were/are kinda established by the firearms mfg's but are not "written in stone" as being something that you and I have to stick with. These twist rates are recommendation's to fill the general public's need to shoot different weight bullets in the same rifle.

For instance, back in 1955, Winchester came out with the .243 and about the same time Remington came out with the 6mm. Win. brought theirs out with a 1-9 (maybe 1-10) twist while Rem. came out with a 1-12 twist. Shooters quickly found out that the .243 would stabilze both light varmint bullets and the heavier 95-100gn bullets, good for deer. The 6mm's 1-12 was only good for the lighter bullets and this error created just enough of a stall for the .243 to gain the shooting publics interest and kudo's. I imagine the 6mm's lighter rounds at slightly faster speed caused alot of deer sized game to "run off", also putting a strike against this round. Rem changed the barrels for the 6mm but the damage had been done.

This was all before my time and I have read it in magazines hundreds of times over the years but illistrates (to me at least) the importance of the right twist rate, especially on new cartridges being introduced to the shooting public. They (twist rates) can make or break a new cartridge.

A good source for twist rate "recommendations" is the bullet/barrel makers. Berger and Lilja immediately come to mind, but are not the only source. You can probably Googe "bullet twist rates" and get a ton of info on the subject. Compare a couple of different bullets from difference mfg's, say a .257 115gn Berger VLD and a Nosler 115gn Ballistic Tip. Look at the differences in overall lengths and bearing surfaces. The ogives are two different examples, the Berger being a "secant" ogive while the Nosler is a "tangent" ogive. Google that (ogive) too. Lots of interesting read.

Hope this clears up some of the confusion for ya. JohnnyK.