BigBfever Report post Posted March 4, 2009 just started reloading a couple months ago and have really got into it, my question is when you have a twist ratio for example 1x8 twist would a 1x9 0r 1x10 be faster? I'm working with high velocity and heavy bullets and I don't want to get to crazy trying to make some thing work that is meant to be. Share this post Link to post Share on other sites
Couzer Report post Posted March 4, 2009 1 in 8 is faster, the bullet will travel 1 full round in turn in 8 inches, so 1 in 9 is slower, 1 in 10 is even slower. Some bullets require a certain spin ratio depending on the weight. If they spin to fast the can come apart in mid air or even tumble. A lot of you reloading books will tell you the recommended ratio. Reloading is super fun, just have to experiment with your stuff!!! But if there is any good advice out there, ask the benchrest shooters what they shoot and load developments they use. They spend a lot of time and a few bucks in shooting! Just my 2 cents Share this post Link to post Share on other sites
matthewp45 Report post Posted March 4, 2009 Also some heavier bullets require more spin to stabilize. So you would want a more aggressive twist for the heavier bullets. Share this post Link to post Share on other sites
BigBfever Report post Posted March 4, 2009 Thanks guy exact info i was looking for Share this post Link to post Share on other sites
.270 Report post Posted March 4, 2009 actually, bullet tumble is usually caused by a twist rate that is too slow. in a given caliber, a longer, heavier bullets requires a faster twist than a shorter, lighter bullet. some calibers aren't twist sensitive at all, like the .277 and .338 diameter. one twist rate is usually good for all bullets. other calibers, the .308 and .257 diameters always jump up here, are real twist sensitive and may require nearly twice as much twist to stabilize heavier bullets in the same caliber as required for lighter bullets. if you want to shoot a 220 grain .308 bullet you need a 1 in 8 twist. a 125 or 110 will probably need like a 1 in 15. bullet length compared to the diameter actually has more to do with it than weight. Lark. Share this post Link to post Share on other sites
krp Report post Posted March 4, 2009 To figure twist for a specific bullet there is the Greenhill formula, for the average guy wanting to customize his hunting gun to one specific light for caliber or heavy for caliber bullet, the quality barrel makers will figure it out for you when you order. Light or heavy is a general rule, length is really the deciding factor. 7mm bullets - 1. 139gr hndy 2. 120gr tsx 3. 120gr nbt 4. 120gr v-max 5. 140gr tsx You can see that the 120 gr bullets I have are the same length as the 139 gr hndy, my 7mm's shoot the 139 well and do the same with the longer 120s. I haven't had as good of luck with the shorter cup and core 120s. You can see that the 140gr tsx is quite a bit longer and shoots well also. Most factory 7mm rifles have a faster twist to stabilize a long 175 gr bullet. If you shoot med to heavy bullets the factory twist works well. If you only shoot light to med and want a new barrel, slowing down the twist would be best. Looking at the 2 tsx bullets, and how long they are for their weight. It shows why a light for caliber tsx shoots so well in factory twist that is designed for what most guys shoot, mid weight for caliber bullets. This is a simple example for a simple guy like me, the experts can get more indepth. Kent Share this post Link to post Share on other sites
