Tweet
In the last year or two I have started hunting in CA. The area I hunt requires non-lead bullets. In trying to work up loads with Barnes TSX and Hornady GMX bullets in my Remington 308 Varminter my luck has not been good. Accuracy has not been that bad, but I can't get the accuracy I can from jacketed lead core bullets. The gun will shoot half minute groups with several jacketed bullets, but so far I have not found any load that produces that result with the copper and copper alloy bullets.
This leads me to the question, what is the determining factor in the rate of twist, length of the bullet, and velocity for best accuracy? From what I read, the formula developed by George Greenhill in 1879, determine correct twist rate for lead core bullets is based on length, not weight or bullet shape.
All the copper and copper alloy bullets are longer than equivalent weight lead core jacketed bullets. Should barrels intended to be used with the longer copper bullets have a higher twist rate than one would select for lead core bullets of equal weight?
This may have been addressed, but I have not seen the article. I am also in the process of working up loads for a Douglas barreled 8mm Remington Mag. Over all accuracy is good. . .heck, it is excellent. But, The interesting part is that my best accuracy with the .323" Barnes 200 gr. TSX bullets is at maximum+ loads with the IMR 7828 ssc powder I am using. I have also read that others have observed that as the velocity increases copper bullets seem to become more accurate.
My first trip to the range was with some old loads worked up before rebarreling. They were beyond max in this barrel. These loads were in brand new Remington cases. After firing, these cases will not hold the primer, due to pocket expansion.
I reloaded new cases with the copper bullets and backed the 84 gr. IMR 7828 SSC load in the old loadings to 83.2 gr. No signs of pressure, but instead of 1/2 minute one hole groups, I am getting 1.5 minute groups. Suggestions! Comments! Should the twist rate be higher for a 200 gr. solid copper bullet than a 200 gr lead core copper jacketed Sierra MK HPBT bullet?
This leads me to the question, what is the determining factor in the rate of twist, length of the bullet, and velocity for best accuracy? From what I read, the formula developed by George Greenhill in 1879, determine correct twist rate for lead core bullets is based on length, not weight or bullet shape.
All the copper and copper alloy bullets are longer than equivalent weight lead core jacketed bullets. Should barrels intended to be used with the longer copper bullets have a higher twist rate than one would select for lead core bullets of equal weight?
This may have been addressed, but I have not seen the article. I am also in the process of working up loads for a Douglas barreled 8mm Remington Mag. Over all accuracy is good. . .heck, it is excellent. But, The interesting part is that my best accuracy with the .323" Barnes 200 gr. TSX bullets is at maximum+ loads with the IMR 7828 ssc powder I am using. I have also read that others have observed that as the velocity increases copper bullets seem to become more accurate.
My first trip to the range was with some old loads worked up before rebarreling. They were beyond max in this barrel. These loads were in brand new Remington cases. After firing, these cases will not hold the primer, due to pocket expansion.
I reloaded new cases with the copper bullets and backed the 84 gr. IMR 7828 SSC load in the old loadings to 83.2 gr. No signs of pressure, but instead of 1/2 minute one hole groups, I am getting 1.5 minute groups. Suggestions! Comments! Should the twist rate be higher for a 200 gr. solid copper bullet than a 200 gr lead core copper jacketed Sierra MK HPBT bullet?
Comment