Which bullet weights with which twist?

MADISON · February 16, 2008, 08:52 PM

Which bullet weights with which twist?

Does anybody have a list of which rifle bullet weights goes with which twist, they can post?
MADISON

Scorch · February 16, 2008, 09:19 PM

Go to just about any barrel-maker's site and you will find a chart outlining suggested twist with bullet weights in different calibers.

NAVET · February 17, 2008, 12:47 AM

This is second hand so take it with a grain of salt. I asked a friend of mine about that very same thing as I am still reading up on reloading BEFORE I buy my first set up. He quoted the Greenhil Formula. I have never put it to the test to see if it's true or if it's a math problem meant to confuse us normal non math geek types.
T=150 X Dsquared / L
T=Number of twists per inch
150 for rounds going less than 1800 FPS. Substitute 180 for rounds over that
DSquared=Bullet diameter squared
L=Bullet length
My only question is there are some pretty wild twist rates out and the math works out sometimes to an impossible number. IE A Ruger Blackhawk in .41M has a 1:20 twist. That works out to an "optimum" bullet length of 1.26075".
Again, I have never tested the formula to see if it works, just passing along info. Personally, it is WAY to much math for me. But IF its any good, it would save time and money by at least getting you in the ballpark. The downside is trying to find bullet length without actually measuring each Manufacturers bullet and weight.

Toolman · February 17, 2008, 09:02 PM

Depends on the caliber. Most bullet manufacturers have that info and will recommend rifling twists for specific bullet weights.
ie: Sierra #1380, 22 cal (.224 dia) 69 gr HPBT-Match says 7"-10" twist barrels.
In my experience with .223 Rem & 5.56 NATO, 36 gr bullets like a 1:12/1:14 rifling whereas 69 gr bullets like a 1:9 rifling. 55 gr bullets in a 1:9 twist barrel have given me decent groups too.
YMMV

February 16, 2008, 09:19 PM	#2
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	Go to just about any barrel-maker's site and you will find a chart outlining suggested twist with bullet weights in different calibers. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

February 17, 2008, 09:02 PM	#4
Toolman Senior Member Join Date: April 7, 2006 Posts: 514	Depends on the caliber. Most bullet manufacturers have that info and will recommend rifling twists for specific bullet weights. ie: Sierra #1380, 22 cal (.224 dia) 69 gr HPBT-Match says 7"-10" twist barrels. In my experience with .223 Rem & 5.56 NATO, 36 gr bullets like a 1:12/1:14 rifling whereas 69 gr bullets like a 1:9 rifling. 55 gr bullets in a 1:9 twist barrel have given me decent groups too. YMMV __________________ Crime Control. NOT Gun Control.

February 16, 2008, 08:52 PM	#1
MADISON Senior Member Join Date: January 1, 2000 Location: Roanoke, Virginia Posts: 2,678	Which bullet weights with which twist? Which bullet weights with which twist? Does anybody have a list of which rifle bullet weights goes with which twist, they can post? MADISON

February 17, 2008, 12:47 AM	#3
NAVET Member Join Date: February 16, 2008 Location: Lansdale, Pa Posts: 25	This is second hand so take it with a grain of salt. I asked a friend of mine about that very same thing as I am still reading up on reloading BEFORE I buy my first set up. He quoted the Greenhil Formula. I have never put it to the test to see if it's true or if it's a math problem meant to confuse us normal non math geek types. T=150 X Dsquared / L T=Number of twists per inch 150 for rounds going less than 1800 FPS. Substitute 180 for rounds over that DSquared=Bullet diameter squared L=Bullet length My only question is there are some pretty wild twist rates out and the math works out sometimes to an impossible number. IE A Ruger Blackhawk in .41M has a 1:20 twist. That works out to an "optimum" bullet length of 1.26075". Again, I have never tested the formula to see if it works, just passing along info. Personally, it is WAY to much math for me. But IF its any good, it would save time and money by at least getting you in the ballpark. The downside is trying to find bullet length without actually measuring each Manufacturers bullet and weight.