Author Topic: Pistol ammo shot in a carbine barrel. (Read 834 times)

JimG · « **on:** October 28, 2005, 10:49:05 AM »

What would the average increase in fps and fpe be when a .40 S/W is shot from a semi-auto 17.5" barrel and not the standard 3.5"-5"? Is there a formula that one can use?

Iowegan · « **Reply #1 on:** October 30, 2005, 04:57:36 AM »

No doubt, there would be a considerable increase in velocity. Energy tracks with velocity so it would increase too. There is no magic formula to compute the difference. Much would depend on the bullet weight and the burn rate of the powder used. The only real way to find out is to chronograph both guns with the same ammo.

R.W.Dale · « **Reply #2 on:** October 30, 2005, 12:02:58 PM »

I've found that 9mm luger gains about 100 to 150 fps when fired through a carbine over pistol velocities, If 40s&w gains at least as much that means 40 from a carbine would pretty much equal 10mm from a handgun. Therefore meaning that the little Hi-Point carbines would probably be faily good brush guns if proper bullet construction is taken into account.

Pinkerton · « **Reply #3 on:** October 30, 2005, 05:54:17 PM »

I have an article in Shooting Times by Sheriff Jim Wilson that is a review of the Ruger PC carbine that compares the velocity of the 40s&w from a P94 and the 16.25" barrel of the carbine. Velocity gains where about 200fps for the lighter bullets and 100-150fps with the heavier wts.

unspellable · « **Reply #4 on:** October 31, 2005, 07:54:38 AM »

Depends very much on the cartridge. The 22 LR reaches it's maximum velocity in less than 18 inchers and then looses speed.

I have data for the standrad pressure 38 Special i na revovler that shows it reaching maximum velocity in an 8 inch barrel and loosing a bit in a 10 inch barrel. A carbine would not have the loss through a cylinder gap so I'd suspect the standard 38 Special might reach its maximum in less than 18 inches.

HAMMERHEAD · « **Reply #5 on:** November 05, 2005, 07:50:32 AM »

The magnum revolver rounds gain the most, the .45acp usually gains the least due to its low pressure.
Lighter bullets will gain more, heavier ones will gain less.
100 to 250 fps will probably be the range of gain you'll get.

BAGTIC · « **Reply #6 on:** November 07, 2005, 12:30:19 PM »

Assuming comparable loads are loaded to the same pressure levels the load with the heavier powder charge will usually show the biggest gains.

For example, a .38 special with a 158 gr. SWC will gain (in an 18 inch vs. 6 inch barrel) about 125 fps when loaded with Unique and about 200 fps and loaded with Blue Dot. That assumes both are loaded to SAAMI maximum pressures, or thereabouts.