Optimal 9mm AR barrel length?

**ABdriver** · 03-25-10, 22:39

Gents,
Seeing as you have a 9mm barrel thread going, I've got a couple of questions maybe someone can answer. I want to build a retro looking 635 upper.
1. Were the original Colt 635's produced with a 10.5" barrel?
2. Most barrels I've found come 1-10" twist except model 1 sales which is 1-15", is there any real issue with the slower twist?
3. If someone has a close up pic of the flash hider/bayonet lug from original 635 upper I sure would love to see one.

My issue is that the barrels by Spikes and RRA look slightly longer than the original Colt barrel to me. The distance between the flash hider and bayonet lug looks longer. Model 1 sales cuts their barrel to 10.25". I like the look of the flash hider almost touching the bayonet lug. However, spending extra money to cut 1/4inch is not in the budget right now. Thanks for the help.

**CRAMBONE** · 05-17-16, 03:28

Necroposting this thread up from the deep. Some of the info is old and new manufacturers have started making 9mm AR barrels. And I don't think my questions warrant a new thread.

I have a AR-9 lower inbound for a SBR build. I'm trying to decide on barrel length and also which manufacturer to go with. My plan is a 3.5-5.5" barrel in a 7-9" rail with my Octane 9 inset into the rail atleast half of the can's length. My goal with the planned upper is suppression. I was first contemplating buying a Colt SMG barrel and having it cut down and threaded by ADCO. Then I noticed Ballistic Advantage makes 9mm barrels and they are on sale right now. Buying on of those would be cheaper than going with the Colt barrel and having it cut, and cheaper than most other makers also. They seem to have a good reputation but they only offer a 5.5" barrel. I have looked at ADCO's barrels but I think they are priced close to the price of the Colt. This will be my first 9mm AR and first full build so any info or tips or guidance is appreciated.

**daniel87** · 05-17-16, 05:45

I would think gtg. They make aero precision barrels. If you do buy make sure to use headspace gages to be sure

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**Lefty223** · 05-17-16, 07:58

Originally Posted by DDLES

Try this site:
http://www.ballisticsbytheinch.com/9mmluger.html

Looks to me like 12 inches is where the curve flattens out for most types of 9mm ammo.

Link was old ... here is the latest to 9mm ballistics:

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

**CRAMBONE** · 05-17-16, 12:53

Originally Posted by Lefty223

Link was old ... here is the latest to 9mm ballistics:

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

Thanks. From what I've read and heard 950 is the "magic number" for suppression. I wish more people made 4.5" barrels.

**wahoo95** · 05-17-16, 13:48

Anything under 1050fps and you should be good. All of your 147+gr is great and hand loaded 124gr and 135gr is good. I like 5.5" for 9mm.

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**CRAMBONE** · 05-30-16, 04:19

I am going with the Ballistic Advantage 5.5" with a 10" ALG rail. They were having a sale on those barrels last week so I grabbed one.

Originally Posted by wahoo95

Anything under 1050fps and you should be good. All of your 147+gr is great and handle a dedicated 124gr and 135gr is good. I like 5.5" for 9mm.

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**blade_68** · 05-30-17, 21:41

I have one 5.5 BA barrel and 8.3 one been good for me so far well over 2 k shoot from them. I shoot with 45 cal suppressor and with 158 gn subs no problems other than finding more of it.