Velocities From 18.5" 9mm Barrel?

#1

Hi,

Has anyone choreographed their 18.5", 9mm Sub? There is a lot of info on 16" barrels, and I’ve read other tests on 18" and shorter, from other brands. There is however, very little on the web that is specific to the 18.5" barrel, Sub 2000 velocities.

Thanks!

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#2

@Yuk, Do you have an aftermarket barrel on your Sub 2000? The barrel length is 16.25" on a stock Sub2000. This is from the Kel-Tec Web search.

The semi-automatic Sub-2000™ is designed to be the most convenient 9mm or .40 caliber rifle available. It’s adjustable and foldable to …

Folded: 16.25”

Barrel Length: 16.25”

Length Collapsed: 29.25”

Overall Length: 30.5”

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#3

Most export, Sub 2000 barrels, particularly to commonwealth countries, have 18.5" barrels. Shorter barrels are illegal in Canada.

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#4

Oh, ok. I didn’t know that our northern neighbors had those restrictions.
My Sierra reloading manual shows the same load for a 4" pistol barrel and a 16-1/4" PCC barrel. The velocity out of the pistol is 1000 fps and out of the PCC is 1350 fps. Taking into consideration that the PCC barrel is 12.25" longer simple math would say that each extra inch of barrel increases velocity about 28.57 fps. Assuming all else is the same that would put the same load out of an 18.5" barrel at 1414 fps. These are just a simple guess though. It is going to be very dependent on if the pressure curve in the barrel is still accelerating the bullet or if in fact the bullet is deccelerating because the pressure is dropping off rapidly due to all powder being burnt before the bullet exits the barrel. I purposely load slower burning powder when reloading for my Sub to get a more even pressure curve.
Bottom line is I can’t answer you question without a chronograph and an 18.5" barrel, I can only make a guess.

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#5

@Yuk, Maybe this will help.
http://www.ballisticsbytheinch.com/9luger.html
Looking at this chart, it does look like most loads from an 18" barrel are slightly slower than 17" barrels, and about the same, maybe slightly better than 16".

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#6

Thanks for you replies Texprep, I appreciate them!
As you have found the information I’m looking for is very hard to come by. It is very clear that velocity tends to drop in a Sub barrel once the length begins to exceed 16", and that drop is not necessarily linear. Just because one brand of 18" barrel produces a certain velocity range, doesn’t mean the 18.5" Kel Tec barrel will be anywhere close to the same. I don’t have chrono to figure it out myself, but hopefully there’s an international owner who’s already gone through the process.
Cheers

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