Some sub  ammo will be super with the longer barrel.
Yes the speed does max out before the 16"
My 12" chrono almost same speed as it did when it was 16"

If you reload these are none issues. For factory ammo, Federal 147 is among the slowest and always subsonic. Speer Lawman 147 will push just over the super mark with the carbine. Hornady 135 is just under.

if you don't go with Rudy (Macon Armory) make sure you get a barrel that has a deep enough chamber... my 16" PSA had to be chamber reamed to  accept my 1.140 hand  loads, and the nitrided barrel is tough to cut with a HSS chamber ream... had to use a lathe

What's the min barrel length for PCC?

you can use SBRs but not "pistols"

Legalities as a different topic.  

I have 4 9mm uppers.  
I have a 10.5 inch barrel to hit the sweet spot of ballistics and barrel length.  Can be suppressed but I don’t, lots of fun to shoot.  I mean it’s super and very accurate.  

An 8.5 inch barrel with above characteristics, but a bit less unwieldy when suppressed.  Very accurate, but had to modify chamber.  

Those both are full auto capable (on the right lower or with a rLL).  

A 4 inch barrel with an older suppressor on it.   It’s not permanently attached but it’s so old and I don’t have a use for it.  I don’t think the barrel is as nice, so not as accurate but fun since it’s so short.  Suppressor is old but barrel keeps most everything subsonic.  Honestly, it’s kinda useless.  

A 5.5 inch barrel from Macon Armory on a pistol.  Quite accurate.  I built this pistol with all left over parts except the barrel, mag well and brace.   Came out nice and is accurate.   I do have the option to suppress this.   I may use it on my NFA lowers.   It’s nice.

Edit.  I’m in the process of moving.  My next firearm purchase will be a nice chronograph.

I have both a 16" and 5.25 taccom

https://taccom3g.com/product/taccom-ar15-ulw-9mm-pcc-barrel/

As the PCC division grows, are suppressors making any headway?

In a podcast I listened to, one match director said that they weren't allowing them due to shot timer inconsistencies. I found this explanation odd since there are shot timers with an adjustable pick-up that can even work with airsoft guns.

For 1000fps or so , a simple laser, level, measuring tape, micrometer, and calculator is all that is needed.

In fact much higher velocities can be dealt with in same manner, but you need longer distances which just makes it harder to do.

Build 2 uppers

Many barrels come w/ 1/2x28 thread


Go the ballistics by the inch website to see velocity changes from barrel length.



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