What would be the ballistics of a 750 grain .50 bmg bullet out of a 20 inch barrel?
It depends on the powder charge, but here is some data for a 750gr A-MAX from a 24" barrel:
Firing a .50 BMG from a 20 inch barrel is about as useful as firing a .30-06 from a 5 inch barrel.
Why would anyone want to do that ?
Just an idea I had, J.
4 inches makes that much of a difference, J? If so, I have never seen a .30-06 with a 9 inch barrel. Magnum research makes a .30-30 BFR w/ a 7.5 inch barrel.
I would suggest that muzzle blast would be somewhat unpleasant…
If, by “ballistics”, you mean muzzle velocity, you should be able to interpolate that easily enough. Most small arms cartridges exhibit similar loss of velocity compared with barrel length.
OTOH, if you actually mean exterior ballistics, you can calculate that using any of the on-line ballistic programs.
Yeah, just velocity. I was thinking in the 2000-2300 fps zone?
With barrels approximately 24 to 30 inches in length, a Cal .50 will lose about 35 fps per inch. But, the shorter a barrel gets, the more velocity will be lost per inch.
So, you do the math. ;-)
2400 to 2600ish then? Ok.
Shot a 16" single shot 50bmg. Guy bought it that short for fireballs and giggles.
Still a very effective plinking round out to past my ability to shoot.
I am not sure how you arrive at 4 inch difference.
The standard barrel length for .50 BMG is 45 in. (Vihtavuori reloading manual; .50 M2 machine gun). The published velocity figures are based on this length, as well as the selection of propellants.
In a 20 in. barrel (thats 5.56 mm M16 barrel length), a disproportional amount of propellant does nothing else than create a fireball and muzzle blast.