? on reloading recipes for 4"

[platoonDaddy]

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.

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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

[Boxerglocker]

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


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

[markm]

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

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.

[Boxerglocker]

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.

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.