Anonymous
I am not a gun expert by any means, so I look at it just from the physics textbook point of view. The pressure behind the bullet decreases as the bullet move along the barrel. I would guess that if the barrel is long enough, the pressure would be insufficient to accelerate the bullet any more and the friction in the barrel would actually slow it down. So probably there is one combination of powder load, bullet weight, and barrel length that gives you the maximum muzzle speed. Putting a load designed for a pistol in a carabine might give you better accuracy due to the bullet spinning faster and aiming with a longer gun but probably it is not going to do much for the bullet speed. If it would significantly increase the speed, probably that load is too much to use in a pistol. just my early morning 2 cents, likely worth less than that. 🙂