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Greenhill formula dead on?

The Greenhill formula says a .277 115grSMK will stabilize in a 14 twist barrel at 2800fps. Think so? I hear there is another formula but I can't seem to put my hands on it. What do you guys think?
 
I think it will.
Using QuickTarget parameters for this bullet including a nose length producing an ICAO BC of .335,StdMetro of .341) I get:
Sg with 14tw under ICAO conditions:
1.11 [McGyro]
1.22 [RSI]
1.31 [Lija]
1.29 [PS rule of thumb]
1.37 [Mine]

Stable is Sg= >1.00

The rule of thumb out of Precision Shooter is
30*Weight/,,Tw/Dia)^2*Dia^3*,Length/Dia)*,1+,Length/Dia)^2))
It disregards velocity,which is minor), and air density beyond standard,which is major). But it's relatively safe, as with Greenhill.
 
Greenhill was for blunt bullets, and isn't a very good prediction for the style of bullets we shoot today.
Don Miller published a great equation in the March, 2005 issue of precision shooting:

Sg = 30*m/,t^2*d^3*L*,1 + L^2))

Where:
Sg is the static stability. Must be greater than 1.0, desired to be at least 1.4 for practical purposes.
m is mass in grains
t is twis rate in calibers per turn
d is diameter in inches
L is bullet length in calibers

I don't know how long the .277 bullet is you're talking about, but using 115 grains, .277 diameter, and 1:14 twist, here are some Sg's for some likely lengths:

If bullet length is: 1.1" Sg is: 0.95
If bullet length is: 1.0" Sg is: 1.25
If bullet length is: 0.9" Sg is: 1.69
If bullet length is: 0.8" Sg is: 2.36

So according to Don's equation, the longest .277 cal 115 grain bullet that you can 'comfortably' stabilize with a 1:14" twist is 0.962". This length gives an Sg of 1.40. Of course, you might get away with up to 1.08", which gives Sg=1.0, but that's not an advisable combination.
Don's equation compares very well with more sophisticated methods of Sg prediction.
Hope this helps,
-Bryan


Edit: You beat me to it Mike! We were thinking the same thing. I take it from your math that the length is 0.99"
 
Yes, thanks for correcting me Bryan,slipped on 30*). I fixed above. I normally use Ro with it as,30/Ro)* yada,yada

I was using .990"OAL
 

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