165 gr bullets in for 1 in10 twist .308
- Thread starter Bigbubba
- Start date
captainmike
CGN Regular
- Location
- GVA- fraser valley BC
take a look a this
- Location
- Golden Lake
Generally the longer, heavier bullets require a faster twist rate to stabilize. My WInchester Model 70 in 6.5x55 has a 1 in 7.87" twist rate as the 6.5x55 was originally designed for long 160 gr bullets. The 1 in 7.87" twist also gives good accuracy with 100, 120 and 140 gr bullets too.
My Winchester Model 94 .30-30 has a 1 in 12" twist rate and is accurate with 100, 130, 150 and 170 gr bullets.
My Winchester Model 94 .30-30 has a 1 in 12" twist rate and is accurate with 100, 130, 150 and 170 gr bullets.
There's actually a formula for determining best twist rate, based on bullet geometry and weight as well as muzzle velocity. I built an excel sheet that calculates true BC, Miller Stability, and best twist rate. PM me if you'd like me to email it to you.
Cheers!
Cheers!
x2. I gotta agree with this one too.
i just started reloading 165 for my 308 and for the life of me i cant get groupings less the 2inches
, i think i may be pulling hard on the trigger as an excuse to go shooting more though haha
The equation may be used as follows, where;
MV = Muzzle Velocity
D = Bullet diameter in inches
L = Bullet length in inches
Twist rate = 3.5((MV^0.5)*(D^2))/L
eg:
Twist Rate = 3.5((2560^0.5)*(0.308^2))/L
= 3.5((50.59644)*(0.094864))/L
= 3.5(4.79978)/L
= 16.799233/1.350
= 12.44 (round this number down according to rules)
= 12:1 twist rate
Hope this helps shed some light on the math side of things!
Moot
MV = Muzzle Velocity
D = Bullet diameter in inches
L = Bullet length in inches
Twist rate = 3.5((MV^0.5)*(D^2))/L
eg:
Twist Rate = 3.5((2560^0.5)*(0.308^2))/L
= 3.5((50.59644)*(0.094864))/L
= 3.5(4.79978)/L
= 16.799233/1.350
= 12.44 (round this number down according to rules)
= 12:1 twist rate
Hope this helps shed some light on the math side of things!
Moot
Last edited:
formula is:
MV = Muzzle Nelocity
D = Bullet diameter in inches
L = Bullet length in inches
3.5 * ((MV^0.5)*(D^2))/L
eg: 3.5((2560^0.5)*(0.308^2))/1.350
= 3.5((50.596)*(0.094864))/1.350
= 3.5(4.799739)/1.350
= 16.7991/1.35
= 12.44 (round this number down)
= 12:1 twist rate
hope this sheds a little light on the mathematical side of things!
Moot
MV = Muzzle Nelocity
D = Bullet diameter in inches
L = Bullet length in inches
3.5 * ((MV^0.5)*(D^2))/L
eg: 3.5((2560^0.5)*(0.308^2))/1.350
= 3.5((50.596)*(0.094864))/1.350
= 3.5(4.799739)/1.350
= 16.7991/1.35
= 12.44 (round this number down)
= 12:1 twist rate
hope this sheds a little light on the mathematical side of things!
Moot
I've found that powder seems to make a difference too. I know it sounds strange! I used these loads:
Winchester 760; 45.5 grains - 2553 MV; produce sub MOA groups at 100 meters
IMR 4064 ; 41.1 grains - 2548 MV; I couldn't get this load to group to save my life. No idea why!
I loaded another lot with W760, lo and behold! Nice tight groups!
Food for thought!
Moot
Winchester 760; 45.5 grains - 2553 MV; produce sub MOA groups at 100 meters
IMR 4064 ; 41.1 grains - 2548 MV; I couldn't get this load to group to save my life. No idea why!
I loaded another lot with W760, lo and behold! Nice tight groups!
Food for thought!
Moot
Very odd...with 168 smk's mine grouped ok with 4064 but was terrible with varget 1:10 twist, 3031 seems like a good test candidate as well
Nothing unusual in that experience at all.
My thoughts are that there is no way to tell on the internet. There is only one way to be sure your gun will shoot your chosen load with the accuracy you want, and that is to try it. Every rifle is a unique individual, and some will shoot a particular bullet/powder combination well, and another rifle of the same make and model may not. Asking on the internet will get you nowhere. Buy some bullets of various types, select a couple of powders, and then start testing.
ackertjosh
Regular
- Location
- Bruce County Ontario
165gr Sierra Game Kings (SPBT,HPBT) are my go to bullets for my dads Savage 110 Trophy hunter in .308. IT will shoot 3/4" groups all day @ 200yrds with 42.5gr of Benchmark in a Remington Case and set off by a CCI BR2 primer.
165 Hornady SST are my good friends GO-TO for his 300 Win mag with a 1-10 twist..
My gunsmith told me a 1-10 twist is the best rate of twist if u plan on hunting with 30 cal. a 165 comes in with just as much energy as a 180 and more then a 150. No Deer, Bear or Moose will tell the difference. But from my experience the 165 always had the accuracy nod.
165 Hornady SST are my good friends GO-TO for his 300 Win mag with a 1-10 twist..
My gunsmith told me a 1-10 twist is the best rate of twist if u plan on hunting with 30 cal. a 165 comes in with just as much energy as a 180 and more then a 150. No Deer, Bear or Moose will tell the difference. But from my experience the 165 always had the accuracy nod.
