Muzzle velocity


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axeman_g
July 14, 2003, 01:42 PM
a quick question I hope.

Given 124 gr NATO 9mm round is fired from a 4 inch barrel and measures 1000 fps, is there a way to figure the muzzle velocity of that same round out of a 6 inch barrel or a 16 inch barrel without using a device???? Rough estimate all I am looking for.

I have a .357 with a 5.5 inch barrel. I want to know the fps of the .357 round out of a 20 inch lever action would be?

Axe

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Mike Irwin
July 14, 2003, 01:46 PM
The old rule of thumb is to add 50 fps. per inch of barrel.

However, that may not work in pistol caliber firearms with longer barrels if you go from a handgun length to a rifle length.

John Ross
July 14, 2003, 02:20 PM
You can get a VERY accurate estimate if you plug all the numbers in to "Suggest-A-Load" available at

http://www.john-ross.net/suggestload.htm

Go to the link 1/3 down the page to download it.

If that's too complicated and you just want the listed .357 mag numbers, it did the calcs and a full strength .357 load will gain about 230-280 FPS, depending on bullet weight, going from a 5.5" handgun to a 20" rifle.

JR

xtarheel
July 14, 2003, 05:39 PM
John: That little DOS program is a real Gem. Even though it is a decade old, with a current powder burning rate chart, you should be able to develop some good starting loads. That program along with another freeware program called PointBlank at www.huntingnut.com and my new crono, I'm off to do some load development. Thanks.

griz
July 15, 2003, 11:38 PM
The 9mm only gains a little from a carbine length barrel.
Because of it's bigger case capacity, the 357 picks up a bunch. IIRC, for the 158 grain bullet, it goes from about 1300 FPS in a 6 inch barrel to around 1800 in a 20 inch barrel.

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