Custom 450b bullet for Ruger American Rifle

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Custom 450b bullet for Ruger American Rifle

Postby Ramson22 » Thu Aug 30, 2018 2:12 pm

I 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?
Attachments
nose ride 454.jpg
nose ride 454.jpg (39.92 KiB) Viewed 4448 times
Last edited by Ramson22 on Fri Aug 31, 2018 6:38 pm, edited 2 times in total.
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Custom 450b bullet for Ruger American Rifle

Postby Ramson22 » Fri Aug 31, 2018 5:42 pm

After some more research. I have heavily modified the design because a 300gr bullet with the parameters of the original was not possible. Also could someone calculate the length of the rear band and of the groove for me. I'm at a total loss on how to, my numbers do not add up to the oal. :?: The data for my rifle is as follows:

Max round length with .452 diameter bullet loaded backwards 1.925
Brass length 1.69
Throat length .235
Groove diameter .452
Bore diameter .4502
Attachments
new 450b.png
new 450b.png (66.87 KiB) Viewed 4416 times
Ramson22
 
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Re: Custom 450b bullet for Ruger American Rifle

Postby Ramson22 » Tue Sep 04, 2018 5:21 pm

Moved this Discussion to Castboolits, feel free to follow along or add help as as you see fit. http://castboolits.gunloads.com/showthr ... bushmaster
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