A good link to barrel twist rates for subsonic ammunition?

[Sid Post]

My web searches haven't been what I hoped for. Lots and lots of wasted time looking at "@#$" that wasn't helpful.

What rate of twist do we need for barrels in common bullet diameters in rifles at subsonic velocities?

What I am looking for is something like:
For .223 up to 62 grains 1x9 is best.
For .223 62 to 77 grains use 1x7.

I am looking for .223, .30, and .338 with bullets weights on the heavier side of the offerings. I am also interested in 6.5 and 6.8 if someone has the data.

TIA!
Sid

[silencertalk]

It is actually bullet-dependent because it has to do with length, not weight. Of course with lead bullets, weight and length is very well correlated.

[Artful]

go here and plug in your numbers

http://www.mountainmolds.com/helpGreenhill.htm

[LR]

Probably best to take conventional wisdom and make it 1" faster for any particular bullet.

[Artful]

Probably best to take conventional wisdom and make it 1" faster for any particular bullet.

Conventional wisdom is greeenhill's formula as far as I have read, where are you finding otherwise?

http://www.recguns.com/Sources/VIIIB6.html

to find out what length bullet will be stabilized in a given twist, use:



L=150 x D x D
-----
T (that is, 150 x D squared divided by T)

where L= bullet length
The number 150 is a constant used by Greenhill and works well at velocities in the vicinity of 1500 fps or greater. At 2800 fps the constant can be changed to 180 with good results.

[Aabid]

For .223 up to 62 grains, 1x9 twist rate is suitable. For .223 62 to 77 grains, use 1x7 twist. For .30 and .338 with heavier bullets, 1x10 or 1x11 may be ideal. For 6.5 and 6.8, 1x8 twist often works well with heavier projectiles.

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