Gunsmithing Saami Min Bore & Groove AREA 308 WIN.

[joey_762x51]

How is the MIN BORE & GROOVE AREA calculated? Just wanted to get a better understanding of how this is figured.
Any help would be great.
Thanks.

 

[Geno C.]

Pi R squared???

 

[GH41]

I are square too.

 

[Davester]

Pi.r^2 isn't the answer as you can tell by plugging in .3 or .308 divided by 2 - you don't come up with the number in the spec. I used calculus but there is probably a simpler way

 

[Geno C.]

Gotta subtract the area that the lands take up. My original post was a joke but I’m pretty sure it’s right.

.0745 without taking the lands into consideration

I’m going to ASSume that it has to do with how tall the rifling can be given a certain number of lands. Fewer lands can be taller and more lands shorter, in order to meet that spec.

If all that shit is right, that makes me sound like a smart sob ?

 

[Davester]

The issue with the trigonometry is that the sides of the lands are straight so calculating the area of a segment omits a small area throwing the calculation off. The bore, rifling depth and number of grooves are all given in the spec. and the cross sectional area is based off the dimensions given.