peashooter 0 Posted December 31, 2007 Report Share Posted December 31, 2007 How does the amount of twist effect bullet weight ie;- whats the difference between 1-8, 1-9 or 1-12 how does it effect a bullet, Cheers Rich Quote Link to post
Deker 3,478 Posted December 31, 2007 Report Share Posted December 31, 2007 How does the amount of twist effect bullet weight ie;- whats the difference between 1-8, 1-9 or 1-12 how does it effect a bullet, Cheers Rich The twist rate (produced by the barrel rifeling) does not have any effect on the bullet weight! 1-8 means a complete revolution of the bullet in the barrel in 8 inches, 1-9 means a complete revolution in 9 inches. 1-10, 10 inches etc etc. So a 1-8 is quite a tight twist and a 1-12 is quite gentle. Individual calibres and bullet weight, size and speed need different twist rates to optimise performance, stabilise the bullet as much as possible and therefore maximise range and accuracy. Sir Alfred George Greenhill worked out the twist rate formula....this is the time honoured formula everyone still works to and the really good news is...it nearly always works HHMMMMM!!!!! Pay attention The required twist in calibres is 150 divided by the length in calibres. So, if you have a 180 grain 30 calibre bullet 1.35 inches long, you first divide 1.35 by .30 to get the length in calibres (4.5). Then you divide 150 by 4.5 and get a fraction over 33. That's in calibres, so to bring it into inches of linear measure, you multiply by .30. It does work...most of the time...please don't ask what happens the rest of the time...George died in 1927! Cheers Deker Quote Link to post
markbivvy 6 Posted December 31, 2007 Report Share Posted December 31, 2007 How does the amount of twist effect bullet weight ie;- whats the difference between 1-8, 1-9 or 1-12 how does it effect a bullet, Cheers Rich The twist rate (produced by the barrel rifeling) does not have any effect on the bullet weight! 1-8 means a complete revolution of the bullet in the barrel in 8 inches, 1-9 means a complete revolution in 9 inches. 1-10, 10 inches etc etc. So a 1-8 is quite a tight twist and a 1-12 is quite gentle. Individual calibres and bullet weight, size and speed need different twist rates to optimise performance, stabilise the bullet as much as possible and therefore maximise range and accuracy. Sir Alfred George Greenhill worked out the twist rate formula....this is the time honoured formula everyone still works to and the really good news is...it nearly always works HHMMMMM!!!!! Pay attention The required twist in calibres is 150 divided by the length in calibres. So, if you have a 180 grain 30 calibre bullet 1.35 inches long, you first divide 1.35 by .30 to get the length in calibres (4.5). Then you divide 150 by 4.5 and get a fraction over 33. That's in calibres, so to bring it into inches of linear measure, you multiply by .30. It does work...most of the time...please don't ask what happens the rest of the time...George died in 1927! Cheers Deker top man deker, happy new year to you. Quote Link to post
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