dieseldogg Posted May 27, 2009 Report Share Posted May 27, 2009 An idle question I am aware that heavier bullets need a higher rate of spin, ie 1 in a lowish no, 1:9 say & lighter bullets get a slower spin/twist However is the rate of twist/spin constant from breech to muzzle? I presume it is Quote Link to comment Share on other sites More sharing options...
cubix Posted May 27, 2009 Report Share Posted May 27, 2009 The twist rate is more to do with stabilising a particular length of bullet, than weight. Weight does tend to have some correlation with length. There is a formula for it. It is the same right through the barrel. Quote Link to comment Share on other sites More sharing options...
Ninj Posted May 29, 2009 Report Share Posted May 29, 2009 Another variable is what the bullets construction is. A ballistic tip will require less to stabilise it than a soft point of the same length. There are charts which show lengths for a given bullet on shoot forum. Quote Link to comment Share on other sites More sharing options...
Ninj Posted May 30, 2009 Report Share Posted May 30, 2009 Goodness me, I'm awfully sorry to be so vague Thatll learn me Quote Link to comment Share on other sites More sharing options...
Harnser Posted May 30, 2009 Report Share Posted May 30, 2009 That is a really vague statement as a softpoint the same same length as a ballistic tip bullet in the same calibre will almost certainly be heavier if both bullets have the same base profile. Ballistic tipped bullets are more than likely to exhibit either a secant ogive or at least a higher calibre multiple tangent ogive whereas a softpoint is almost certainly a tangent ogive with a traditional radius. If you want answers, put your data into the grrenhill formula and see what comes out, be aware though that some modern bullet designs need different constant values due to the above mentioned factors, the formula was first developed when a tangent radius flat base bullet was the norm and since now we are using bullets with the aforementioned secant radius and boat tailed profiles, overall bullet lengths/weight ratio has changed greatly and it is length that is more critical. God ,that sounds complicated fister , I just buys my bullets ,load im and shoot im . Harnser . Quote Link to comment Share on other sites More sharing options...
dieseldogg Posted June 1, 2009 Author Report Share Posted June 1, 2009 Erm, Perhaps poorly worded but my origonal "idle" question was about twist rates, being fixed? or variable? from breech to muzzle No wiser Just perhaps a little better informed cheers M Quote Link to comment Share on other sites More sharing options...
henry d Posted June 1, 2009 Report Share Posted June 1, 2009 ......It is the same right through the barrel. :blink: Quote Link to comment Share on other sites More sharing options...
chrisv Posted June 1, 2009 Report Share Posted June 1, 2009 (edited) Henry is correct, mostly. The "gain-twist" barrels that Fister refers to are becoming available. They increase the twist rate as the bullet travels down the barrel. I think the theory is that it gives the bullet an easier time as it goes through the barrel. From a quick look on the web it looks like they are popular for muzzle loaders as well as the artillery uses Fister mentioned. Edited June 1, 2009 by chrisv Quote Link to comment Share on other sites More sharing options...
Andy H Posted June 1, 2009 Report Share Posted June 1, 2009 Gain twist rifling has been about for some time it was used in the manlicher carcano that lee harvey oswald used to assasinate JFK. Quote Link to comment Share on other sites More sharing options...
taz24 Posted June 1, 2009 Report Share Posted June 1, 2009 Gain twist rifling has been about for some time it was used in the manlicher carcano that lee harvey oswald used to assasinate JFK. Ah but did he?? Are you sure it was'nt the guy on the grassy Knoll :yp: taz. . Quote Link to comment Share on other sites More sharing options...
taz24 Posted June 1, 2009 Report Share Posted June 1, 2009 (edited) . I watched a program on tv the other day about the development of guns and it was stated that Whitworth developed a gun with a twist every twenty inches when the standard was one twist every seventy inch. They demonstrated the groupings and the difference between Whitworth's rifle and the one in use at the time was hugh. The Whitworth rifle was hitting a patern of two to three inch at two hundred yards where the standard rifle was spread over about a yard. Apparently Queen Victoria shot the thing and scored a bullseye at two hundred yards. The powers to be refused to accept the idea so Whitworth took is idea to the USA and it was used in the Springfield rifle I think. Cheers taz. . Edited June 1, 2009 by taz24 Quote Link to comment Share on other sites More sharing options...
Andy H Posted June 1, 2009 Report Share Posted June 1, 2009 Queen victoria did fire a shot at bisley and hit the metal gong used as a target but the rifle was clamped into a rigid stand and Queen victoria pulled a string connected to the trigger. Quote Link to comment Share on other sites More sharing options...
dieseldogg Posted June 2, 2009 Author Report Share Posted June 2, 2009 Probably wondering why the champange bottle failed to appear Quote Link to comment Share on other sites More sharing options...
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