9mm AR, Short vs. Long

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Djb1

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I'm at the point in my collection where I really want a 9mm AR.
I was considering the fxp-9 but I can't really take advantage of the non restricted aspect nor do I reload so I don't think I would get any advantage from the longer barrel length.
My question is: Is there a difference between a 5" barreled ar vs a 10" barrel in ballistic performance? I would love a super short 4.5" barrel but I already have a pistol and I'm wondering what the accuracy and ballistics would be in a rifle platform.
 
They are usually a range plinker so ....

The shorter the better....

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Get a short one. It's restricted by default by virtue of being an AR so you might as well get something for fun. 9mms aren't suited for anything longer than like 100m anyway since they drop like lead balloons at range. Just make sure to get a hand stop so you don't blow your hand off for the really short ones!
Also barrel length doesn't do that much for velocity and therefore trajectory for 9mm - you get something like only a 10 percent increase in velocity if you get an 18" barrel versus something like a 10", and that only increases by about 15 percent if you start from a 5"er depending on bullet weights.
If you wanted a NR 9mm, I'd for sure recommend a long one just so you can have fun in the woods, but since it's an AR you're up shet creek.
Finally, for a deticated lower, get a Glock mag one. It'll give you an excuse to get a Glock if you don't already have one and 10 rounds is nice instead of 5.

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Djb1 said:
My question is: Is there a difference between a 5" barreled ar vs a 10" barrel in ballistic performance? I would love a super short 4.5" barrel but I already have a pistol and I'm wondering what the accuracy and ballistics would be in a rifle platform.
Click to expand...
It is a 9 mm you are going to use it on targets that is less than a 100 m, the differences between 5" vs 10" is not going to be noticeable on a range blaster, go with the length you want and don't worry about.
 
My 9mm AR has a 12 inch barrel, great for shooting out to 100 yards which is limited mostly by the Aimpoint T-1 and my eyes. It's a lot of fun and is very maneuverable. I like a little longer barrel just so there is something to hold onto when shooting and find that a 12 inch barrel with a nice free float forend is about perfect for me.

EoTech has been swapped for a T-1, the stock is now a Magpul CTR, and it now has an MOE+ grip. I need a new pic :)
That's an ALG Defense forend
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I went with a 7" simply because of hand guard options. I think a 4-5" barrel is too short, unless you're one of those guys that holds the mag well when you shoot.
 
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