? on reloading recipes for 4"

General Firearms Reloading & Ammunition
1

Searching for a recipe for my G17, I located the following for 115 & 124 grain. It states fps in 4" pistol barrel, does that mean in my G17 the fps will be less? As you can tell from my question, I am swimming up stream.

9mm Luger (9x19)

115 grain Hornady HP-XTP (.355") bullet, 6.2 grains HS6 powder, Win. WSP primer, Hornady case. MV 1100 fps in 4" pistol barrel. (Based on the Hornady Handbook, Sixth Edition.)

124 grain Hornady HP-XTP (.355") bullet, 5.9 grains HS6 powder, Win. WSP primer, Hornady case. MV 1050 fps in 4" pistol barrel. (Based on the Hornady Handbook, Sixth Edition.)

http://www.chuckhawks.com/handgun_cartridge_reloading_data.htm

2

The longer barrel, higher the utilization of pressure thus in most cases higher velocities.

3

The pressure isn’t any higher… it’s just more effective use of the pressure from the output charge. You’re using more of it with a longer barrel.

4

You are correct forgot a very important word there. (see edit)The controlled expansion of gases from burning gunpowder generates pressure (force/area). The area here is the base of the bullet (equivalent to diameter of barrel) and is a constant. Therefore, the energy transmitted to the bullet (with a given mass) will depend upon mass times force times the time interval over which the force is applied. The last of these factors is a function of barrel length. Bullet travel through a gun barrel is characterized by increasing acceleration as the expanding gases push on it, but decreasing pressure in the barrel as the gas expands. Up to a point of diminishing pressure, the longer the barrel, the greater the acceleration of the bullet.