I am going to be doing a shorty 9mm build in the future and was wondering if anyone knows the "optimal" barrel length for the 9mm round?  This would be the length that you get peak velocity without seeing it drop off due to extra barrel travel..... Like with a .22RF, they say 16in is the "best" length as you really don't gain any velocity after that much.  

I want the barrel to be short, but not too short and I need it to make it out of the FHG because I don't want it to be a dedicated suppressor host.  I will have a 3 lug adapter to put in it to use the suppressor when I want but I want to be able to shoot it and have it look like a normal rifle, not a FHG with bullets flying out of it

Thanks guys!

got me kind of wondering myself.  gonna have to keep tabs on this thread!

HK says 10" for +P 9x19 ammo.  I haven't seen any test data to support that.

Optimum barrel length and powder  kinda go work together,  but  8" to 10.5" seems to be the common lengths used.

HK std MP5 family 8.7"

Colt SMG  10"

Uzi SMG  10.25"


Handloading with medium speed powders for 9mm will get you higher velocity than std off shelf loads blended for 4-5" inch barrels.    I use 3N37,  AA-#5, AA-#7 for heavy 9mm Uzi loads,  slowfire MAC gets 115gr FMJ w/WST.

Thanks!  

I asked the same question some time ago.
Some interesting comments came back.
(1) The 9mm was developed as a pistol round, therefore a "short" barrel is OK. An Uzi MG barrel is short. 10" seems to be good consensus.
(2) I have a 16" barrel on my 9mm and it seems to work fine. I don't know the bullet speed.
(3) I did some research a few years ago on barrels and ballistics - just for fun. One key point was tha often a round has an "optimum" barrel length where all the powder will be expended to attain max rate. The 223 was optimized for approximately to 20" roughly. Little is gained beyond 22" or even 24".
If the 223 barrel is shorter than 20" then speed is lost. Regrettably, I don't know the "optimum" barrel for the 9mm - but (1) at 6" - 10" may be a good starting point - SBR tiome????

Quoted: I asked the same question some time ago. Some interesting comments came back. (1) The 9mm was developed as a pistol round, therefore a "short" barrel is OK. An Uzi MG barrel is short. 10" seems to be good consensus. (2) I have a 16" barrel on my 9mm and it seems to work fine. I don't know the bullet speed. (3) I did some research a few years ago on barrels and ballistics - just for fun. One key point was tha often a round has an "optimum" barrel length where all the powder will be expended to attain max rate. The 223 was optimized for approximately to 20" roughly. Little is gained beyond 22" or even 24". If the 223 barrel is shorter than 20" then speed is lost. Regrettably, I don't know the "optimum" barrel for the 9mm - but (1) at 6" - 10" may be a good starting point - SBR tiome????

SBR is already in the works  Pending since May 2nd

I have a LRM M169 and just bought a AAC Evolution 9 so I will def. be doing additional 9mm uppers.  From pics I have seen, I think either a 10.5 with FSB or a 8-10 (long enought to clear the FHG's) with a rail mounted sight will be my options.

Thanks for all the info fellas