Thursday, April 6, 2017

Early Telescopic Sight

I saw this once before, and fortunately found it again:
Mr. Owen Biddle is desired to procure a Rifle that will carry a half pound Ball, with a Telescope sight…. [Pennsylvania State, Colonial Records of Pennsylvania (Harrisburg, Penn.: 1852), 10:332]
Telescopic sight in 1775?  1/2 pound ball is 227 grams.  I'm told this is about a 1 1/4" bullet.  No, it's .66 caliber. V=4/3*pi*r^3 and lead is 11.3 g/cc.  r=0.66, so 1.32 caliber.

4 comments:

Rusty Miller said...

A 1/2 pound lead ball (a 2-bore) is more likely about 1.25" in diameter.

James Gibson said...

Agree, by the math its a 1.33 inch diameter. Clayton, you forgot that the equation for the volume of a sphere uses the radius. So you are correct that the bullet would be 0.66 in radius. Something about this however reminded me of passages in Hicks on Wall Guns. In 1847 two experimental wall guns were made at Springfield and Harper's Ferry. The important point in the Hicks reference is that the bullet was to be conical and weighed 3 ounces (actual gun bore being 0.75). So I would suspect your reference to a half pound ball in 1852, is actually a conical ball and not a true sphere. I find references to the standard Minie ball (0.58 bore) being 500 grains in weight or 1.14 ounces. In short I doubt you can compute the actual bore of this 1852 rifle based on the weight of the bullet. Its going to be large, but not 1.33 inches in diameter.

ErolB1 said...

The radius of a 1/2 lb lead ball is ~0.66 inches. The diameter, of course, would be twice that.

dittybopper said...

Yeah, it's definitely *NOT* .66 caliber. I shoot a .62 caliber and the balls weigh about 360 grains (7000 grains in a pound). That's about a 20 gauge. Even a 12 gauge (up near .75 caliber) would mean there are 12 balls per pound of dead soft lead that would fit. A half-pound ball means 2 bore, and 2 bore is about......

1.67 / cube root(2) = ~1.16 inches in diameter.

Checking to make sure that's right for a 20 gauge:

1.67 / cube root(20) = 0.615, which rounds up to 0.62".