Greenhill's Formula vs. Reality

[Koa]

I have been plugging away at Greenhill's formula figuring out the "ideal" length bullet for given twist rates for some guns. I'm wondering how accurate Greenhill's formula is for small arms, general speaking, and whether anyone out there has done any testing to see for themselves. For instance will going up or down 0.10 or 0.20 inches make much of a difference?

 

[ldg397]

I was wondering the same thing. I worked through the calcs on my .260 and it suggests I should use a hornady sst 140 grain for my barrel twist. I haven't loaded them yet but I will post any results I find.

Also is there anywhere you can find the bullet length for different bullets so you don't have to buy them to find out for your calcs. I need some bullet lengths for .308 bullets.

 

[JD338]

I am aware of Greenhill's formula but I would go to the barrel manufacture and get their advise. That, along with your gunsmith should get you where you need to be.

ldg397,

What .308 cal bullets are you interested in? I have a few of different makes and weights in my shop that I can measure for you.

JD338

 

[Antelope_Sniper]

JD +1

 

[ldg397]

I am aware of Greenhill's formula but I would go to the barrel manufacture and get their advise. That, along with your gunsmith should get you where you need to be.

ldg397,

What .308 cal bullets are you interested in? I have a few of different makes and weights in my shop that I can measure for you.

JD338

I was just trying to use the formula to select a bullet for new sako 85 in 30-06. I have the 165 Accubonds.

I believe I have a 1/11" twist. My theory is it will prefer the 150, 165 or 180 grains. I wouldn't mind dimensions for Accubonds, Partitions, Gamekings, Interbonds, SST, A Frame, Sciorroco??? Basically whatever you got. The formula says the 165 grain AccuBond is pretty close to ideal under 2800 fps but could be a hair longer, I might try the 168. Has anyone tried to use this to help bullet selection for a load rather than going out and buying a ton of bullets??

 

[Koa]

If you go to the shooter's pro shop they have listings for bullet length under the specifications for each the factory second's. I was looking myself yesterday and was not able to find much info from other manufactures.

Also in my search yesterday I found contrary information from several different sources regarding Greenhill's formula. Some list using the 180 value for speeds above 1800 fps and some list using for speeds above 2800 fps. Anyone have a definitive answer on this one?