Optimal 9mm AR barrel length?

[ArchAngel]

Does anyone know what the optimal barrel length is for 9mm rounds for max velocity?

Say, standard 115gr FMJ rounds for start.

I know different loads could change optimal barrel length but anyone have a ballpark?

I was just wondering if it was in SBR range or if the 16" was getting close.

Thanks in advance.

[45-Bravo]

I thought I read somewhere that 10.5" was optimum for 9mm ?

I may be wrong though.......

[-Wes-]

Hard to get a deffinitive answer on that. Many people base it on what companies do such as an MP-5 is in the 8" range I think.

I just searched and searched and can't find a good site with velocity specs to compare. Lots of charts out there but they're all different loads with different barrel lengths.

One site quoted a PMC test done on penetration not velocity. It said something to the effect that extremely short barrels that don't produce enough velocity will penetrate further because the bullet won't expand.

Another chart I saw was purely built off theoretical numbers. Velocity was graphed rising all the way to the end of the chart at 16". The criticism it brought on was that at some point the length of the barrel causes friction and it should drop off.

I guess until someone chrono's the same ammo from 16" and cuts/re-crowns an inch at a time, we'll never know.

[JeepDriver]

I have a 9.25" TOS barrel on one of my SBR's and It's every bit as accurate out to 25yards as the 16" guns. I can shoot it out to 75 yards easily hitting a 12x12 steel plate.

I don't know about velocities in the 9.25" barrel, but the 16" barrels I chronoed a while back were only running 100 to 150 fps faster.

WWB VP was averaging 1269,
Ranger 127+P+ was 1401,
Golden Saber 124+p was 1277,
Speer 124 +P was 1418 (and the most consistiant),
Federal Hydra Shok 124gr was 1207,
Mag tech 115gr was 1237.

I keep a mag of Ranger 127+P+ loaded, not that I'd grab the 9mm AR for defence, But It's nice to have a mag ready ;)

[Steve-HSA]

I tested this a couple of years ago with a 5", 10.5", and 16" barrel.

Ammunition used was the same, though I can't remember if it WWB or Magtech.

I'll have to search my PC for the results, but if I remember correctly statistically there was little difference between the 10.5" or 16" barrel. While I did not measure accuracy to the fractional inch. Both barrels where equally accurate out to 100 yards from the bench with iron sights.

[SuicideHz]

Will subsonic 147gr. stay subsonic out of a 10.5" 9mm barrel if it is out of a pistol barrel?