Mathematics for dummies

[lilguy43uk]

Can some one point be to an easy method of converting muzzle velocity to ft/lbs please. Just had a MV reading of 690fps but I have a mental blockage when it comes to maths.

Ta

[NigelG]

PM sent

[NigelG]

Or, if you don't wish to know how it works

Weight of projectile in grns (not grms) x velocity x velocity all divided by 450800

[tacfoley]

http://www.shooterscalculator.com/bu...tic-energy.php

Took almost three and a half ten-thousands of a second to find, too.

BTW, if your pellet weighed 15gr then the ME is 16ft lbs.

tac

[sidesy]

Can some one point be to an easy method of converting muzzle velocity to ft/lbs please. Just had a MV reading of 690fps but I have a mental blockage when it comes to maths.

Ta

a phone app.......?

[sarge4318]

a phone app.......?

Yes, there's plenty of them for Android (and I guess for apple too). Most are marketed as airgun muzzle energy or ballistic calculators but you can input any likely MV and bullet weight.

[pbranthwaite]

Or, if you don't wish to know how it works

Weight of projectile in grns (not grms) x velocity x velocity all divided by 450800

I always thought it was 450240

[xbow]

I always thought it was 450240

Yup.

http://www.pyramydair.com/article/Wh..._August_2003/5

[Rich]

The constant is 2 x 7000 (grains per pound) x gravity in ft/sec^2.

450240 comes from using 32.16 as the value for gravity.

[NigelG]

to be pedantic, it's 32.174 poundals in a pound, which gives 450436
Rounded up to 32.2 for ease if just doing it long hand
But..... If splitting hairs then the correct number should be used, it could make that difference of 0.01 ft/lbs

[MikB]

to be pedantic, it's 32.174 poundals in a pound, which gives 450436
Rounded up to 32.2 for ease if just doing it long hand
But..... If splitting hairs then the correct number should be used, it could make that difference of 0.01 ft/lbs

Agreed. It's what I've always used - or to be even more pedantic 450436.68 (can't remember, but think I was working from the ISO standard G converted to fps/s). Don't know if a court case has ever turned on that, though.

Regards,
MikB

[El Garro]

If it goes through to the end of the bra section in the catalogue you'll be alright.
(That's from the front by the way )

[xbow]

Or "S" in the yellow pages.

[markH]

I've been using 450240 since I read it in Airgun World in about 1979. I don't suppose it would make a lot of difference but it would be nice to get a difinitive answer as to which is correct.

[airgunnut]

I've been using 450240 since I read it in Airgun World in about 1979. I don't suppose it would make a lot of difference but it would be nice to get a difinitive answer as to which is correct.

I have always used 450240 so has every shooter I know
The difference between 450240 and 450436 will be small
There is the fact that 450240 is easier to remember (it seems to roll of the tounge better!)