How many RPM's is a bullet rotating fired out of a barrel with a 1:10 twist at 2700fps ? I came up with 3240 times per second or

[jhjimbo]

How many RPM's is a bullet rotating fired out of a barrel with a 1:10 twist at 2700fps ? I came up with 3240 times per second or 194,400 PPM's am i correct?

[99explorer]

I come up with the same numbers. 2700fps X 12" = 32,400 ips divided by 10" = 3240 rps X 60 = 194,400 rpm.
I do not have the formula for this, so I'm using common analysis and everyday math skills.
I hope we're right.

[Guest]

Close enough. Anything you hit with said bullet will not care about the rpms.

[Treestand]

Ditto~99 +1

Close Enough.

[jhjimbo]

No wonder the old .223 rifles with 1:9 twist would not stabilize the heavy bullets. I did a comparison and it takes 16% more revolutions to stabilize a 75gr in 1:7 twist over the 55gr in the 1:9 twist. I had a rifle with the 1:9 and it would keyhole the heavy ones.
The difference in the example is 705 feet per second increase in revolution for the 75gr. Just curious.

[99explorer]

Also, at a lower velocity, the heavier bullets would have a slower rpm twist.

[jhjimbo]

99explorer
the example i used was
55gr 3200 velocity 1-9 twist revs per second 4266
75gr 2900 velocity 1-7 twist revs per second 4971

[99explorer]

The math checks out, without rounding up for fractional differences.
Can we assume the 1-7 twist at 2900fps stabilizes the 75-grain .223 bullet?
I have a friend with the same problem.

[jhjimbo]

i used 75gr in the example, heaviest i have loaded is 62gr and they shoot fine.