Check out ballisticsbytheinch.com and you will see different barrel lengths and grains.

 

How do they test all those guns and not one Glock?

That sort of has to be deliberate.

 

Looking at Ballistics by the Inch the increase in velocity is small. For non plus P ammunition there is virtually less if any rise.

Seems like your advantage is with plus P ammunition

I chose a shorter barrel to take advantage of subsonic ammunition with a suppressor.

In the end you should check with ammunition you’d actually use and look at those charts.


http://www.ballisticsbytheinch.com/9luger.html


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Thanks for posting this.

It seems I get about a 25% increase in muzzle energy out of an 8" over a 4" handgun with my 115gr standard velocity hollow points. Not bad.

The increase in energy seems to be about 28% higher than a 4" handgun when using a 10" to 11" barrel and 30% higher using a 16" barrel.

Sounds kinda like an old federal +P+ round in terms of velocity. That could be nasty.

 

A longer barrel gives you the opportunity to benefit more from a heavier grain. I’d recommend going with 147s from a carbine. But 124s will be fine too.

9mm continues to gain in velocity up until 16” or so. I’d recommend the 11” barrel as that will be enough longer to start adding. 8” is kinda meh.

 

124nato works really well in my AR9 especially since the AR9 bolt is so heavy. The extra kick seems to make the thing cycle well.

 

Great info in here! Thanks for the replys.

I would like the use the heaviest gr bullet that makes sense - perhaps ideally 147gr.
Seems like either an 8 or 11 barrel could be significant gains over a standard handgun.

is +P or +P+ even needed? Aren't the +P's intended to short barrels?
Not saying a +P could hurt in a longer barrel though, right?

 

I chose an 8 inch AR9. While the velocity increases with a few more inches in barrel length, to me those extra inches really don't boost 9mm energy to some significally higher power category so maneuverability was more important.

 

There's a thread here with video-ed testing of three kinds of 9mm ammunition in three different barrel lengths. I watched it once, then it disappeared into the multitude of threads and I've never been able to find it again. I believe the thread included a Massad Ayoob article on mob violence......

 

The old school hollowpoints would start fragmenting if the got going too fast is they were on the light side. The 147 grain bullets were hard to open up with shorter barrels because they didn't have the velocity. Subguns they would open up.

New bullets have an optimal "window" in which they expand as designed. We had a chart from Winchester with their various Ranger rounds with their velocity windows. It was fascinating to see the +p .45 had a higher window than the standard pressure. The 9mm had 3 choices, 3 weights, two standard, one +p.