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Old May 13, 2011, 04:26 PM   #1
bigbaby
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question about muzzle velocity

I take both a model 627 357 pistol and a lever action carbine in 357 to the range. The rounds I usually use are 142 grain fmjtc. The ballistics report on them from the maker says they have Muzzle Velocity: 1420 fps; Muzzle Energy: 650 ft. lbs, but it says nothing about how they measure it. Is it from a long barrel pistol like a model 627? If so how much more muzzle velocity would it have from the carbine?
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Old May 13, 2011, 07:26 PM   #2
hounddawg
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according to Chuck Hawks site muzzle velocity from a .357 is measured from a handgun with a 4 inch barrel

http://www.chuckhawks.com/357magnum.htm

then if ya go to ballistics by the inch site you can get a good estimate for your carbine

http://www.ballisticsbytheinch.com/357mag.html
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Old May 13, 2011, 09:26 PM   #3
jmr40
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The only way to know is to buy a chronograph. Anything else is just a SWAG. It my be close, it may not. Individual guns with equal length barrels will often show very different velocities with ammo from the same box.

There is no math formula to accurtely predict what will happen. There are too many variables.
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Old May 14, 2011, 12:27 AM   #4
JohnKSa
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To add to what has been said, if there is no information provided, the assumption is that revolver ammunition velocity is measured with a 4" vented test barrel in an attempt to replicated the velocity expected from a 4" barrel revolver.

It may not be the correct assumption all the time, but I don't know of a better one in the absence of any information to the contrary.
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Old May 14, 2011, 09:47 AM   #5
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It depends on the powder used to propel the bullet.

There is no way of knowing the velocity of a given load without running it over the chronograph, especially if you're trying to know what a single load is doing when fired from a revolver vs a carbine.

For example, I've got one .357 magnum load that gives me 1300 fps from my revolver and 1600 fps from my carbine. This load features a 180 grain gas-checked bullet and Hodgdon L'il Gun powder. It's a great load and when you touch it off, you know you've got a magnum in your hand. That 300 fps difference between the handgun and the carbine is actual measurement, shot across my chronograph.

On the other hand, I've got a target load that features a small charge of Bullseye powder and a 148 wadcutter bullet. It gives me 680 fps from my handgun. When I ran that load through my carbine, I found that I was only getting 606 fps from the 16" barrel. I speculate that the small charge of fast powder was running out of pressure in that 16" barrel and the bullet was slowing from friction. I stopped running that load through the carbine. I don't want a bullet stuck in the barrel by accident.

Short answer: Unless you run it over a chronograph, you don't know.
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