Custom 450b bullet for Ruger American Rifle
Posted: Thu Aug 30, 2018 2:12 pmI have been messing around for a week trying to design a custom cast bullet mold for power coating to use in my 450 bushmaster Ruger bolt action rifle. The groove diameter of my rifle is .452 so I want a bullet with a diameter of .454. What I would like is a bullet with a nose that rides the bore allowing me to use longer bullets with a better BC. I do not think that this bullet needs to be over 250gr - 300gr. The problem Im having is that I have never designed a bullet before. Im having a very difficult time trying to match the twist rate of the Ruger which i have read is 1/16 i do not seem to be able to come up with a design that has a twist rate faster than 1/33 also my bullets weight is much to heavy as cast out of pure lead 373grs. What I have so far is in the picture, all measurements are in inches. Intended velocity is no more than 2000fps with this powder coated bullet.
The calculated data is as follows:
velocity, Ballistic coefficient, twist rate at which bullet is stable
mach .05, G1BC.23, Twist 33.5
mach 1.0, G1BC .27, Twist 39.2
mach 2.0, G1BC .27 , Twist 38.2
Center of gravity from nose .574
My questions are:
if I add lube grooves or a groove to the base, to lower the weight will that make the bullet more nose heavy and raise the spine rate closer to 1/16? If not does that fact that stabilizing twist 1/33 is so much slower than that of the rifle 1/16 matter, over stabilizing is not detrimental to accuracy is it?
The calculated data is as follows:
velocity, Ballistic coefficient, twist rate at which bullet is stable
mach .05, G1BC.23, Twist 33.5
mach 1.0, G1BC .27, Twist 39.2
mach 2.0, G1BC .27 , Twist 38.2
Center of gravity from nose .574
My questions are:
if I add lube grooves or a groove to the base, to lower the weight will that make the bullet more nose heavy and raise the spine rate closer to 1/16? If not does that fact that stabilizing twist 1/33 is so much slower than that of the rifle 1/16 matter, over stabilizing is not detrimental to accuracy is it?
The data for my rifle is as follows: