I decided to pre research this question rather than just post it, but what is the difference between something like a 4 inch barrel and a 10.5 inch AK-V barrel on a chronograph? The answer seems to be about 200 feet per second on 115 grain ammo, based on a youtube video I saw. Anyone done any first hand experimenting with this? No real reason other than curiosity.
FWIW… here are my results from a 16" 9MM barreled AR.
You might be able to “guesstimate” velocities, or at least have a vague idea of what to expect.
129 different factory loads tested.
https://www.ar15.com/forums/ar-15/16andamp_quot__9x19_AR15_Carbine_Chrono_Test_____129_OEM_rds___52_more_added_May_7th__/16-712312/
One of these “free time days” ( Lol ) I intend to shoot the left over rounds through my 10.5" AR upper.
It is an all day project, to say the least.
Thanks, that’s a lot of work.
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Here’s a website that gives 9mm muzzle velocity “by the inch”, starting with 2" barrel all the way up to 18". Not sure how old the data is but it’s fun to look at and play with in Excel. These guys did a lot of work (and for other calibers too).
http://www.ballisticsbytheinch.com/9luger.html
The attached chart is extrapolated from the 9mm data (used their data in excel to create):
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Based upon testing with various 9mm rounds a ~7.5" barrel length is optimal for max velocity at around 1280 FPS. Longer barrel lengths drop off in FPS until you get to a 16" barrel length and then it rises to about 1200 FPS on average.