Does any know what size gas port a DD 16" M4 profile barrel would have?

AR/M4 AR Technical Discussion
1

Pretty much what the topic asks. I have a Daniel Defense 16" M4 profile barrel with their low profile pinned gas block and I’m curious to know if anyone knows what the gas port size is? I’m going to send the barrel to ADCO and have them cut it down to 10.3 for my MK18 RIS II build and I assume I’m going to need gas port work. Everyone seems to want these Western Sports DD 10.3 inch barrels because of the smaller gas port size and I thought the gas ports were smaller on 16" profile barrels as opposed to say the 10.3. Was thinking this might give me the chance to start with the Mil-spec offering gas port size. I know DD’s 10.3 inch Military barrels have a smaller gas port than the commercial versions.

Will be running a SF SOCOM RC can on this.

2

Barrel Length (in) Barrel Diameter (in) Distance from Muzzle (in) Min Port Size (in) Max Port Size (in)
11.5 .625 3.850 .081 .089
11.5 .750 3.850 .086 .094
14.5 .625 8.375 .063 .078
14.5 .750 8.375 .070 .086
16 .625 8.375 .063 .078
16 .750 8.375 .070 .086
20 .625 6.875 .086 .093
20 .750 6.875 .093 .096
24 .825 N/A .089 .089

did you try contacting DD?

3

Those port sizes seem too big IMO. Are these your specs or DD’s?

4

Neither…this is all I could find searching. That’s why I mentioned contacting DD direct. And if you read the break down, port sizes are listed as Min/Max.

5

If you have the barrel in hand, just remove the block and measure the port.

You’re on the right track with the plan, just need to verify the size.

Also, ignore the chart that was posted. It’s been re-posted a zillion times around the errornet and is not good information.

6

There is no minimum and maximum for port sizes. There is MILSPEC correct and other. The correct size for an M4 carbine gas system is .063 inches. A 20" rifle is .093. There is no spec for a middy, but most quality companies make them from .076-.080.

7

The Crane spec for a 10.3/10.5" MK18 is .071 inches. Very few companies do that. The DD barrels I have seen are very close to the .063 size.

8

looks accurate to me…

9

No, it’s not accurate. Because min./max. is incorrect. It’s either ported correctly or it’s not.

10

The reports I have read from DD MK18 owners (which will be me next week) list the port to be closer to .081…and are obviously over gassed to handle crappy ammo. Has DD recently made changes to these measurements?

http://www.ar15.com/forums/t_3_118/647393_Danial_Defense_10_3andamp_quot__barrel__what_size_gas_port_.html

11

So you are saying there is no deviation at all from the thousands of barrels being produced?

12

Well according to a thread in another dimension where chat is specifically about Mk18’s, it sounds like DD has two versions of the 10.3 inch barrel. The military has and purchases their Mil-Spec .071 barrel, which per Daniel Defense they only sell those to the military.

Then for the civilian market they offer the 10.3 inch barrel in a .081 for exactly the reason that you stated, crappy ammo.

Sounds like Western Sports had gotten their hands on a military overrun of DD 10.3" .071 barrels so those are apparently floating around.

Side note looks like my barrel is roughly .064’ish so basically I can do whatever I want with it.

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13

Which is why I was asking…interested to know exactly what MK18 DD barrels he is inspecting and measuring at .063?

14

Sounds like a 16 inch

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15

You need to read more and obtuse less. I was referring to their carbine 16" barrels.

16

I never said DD MK18’s were made to that spec. I was answering his multiple statements. I am not going to breakdown and Barney everything, especially when much of this has been discussed here before.

17

Do you know what an acceptable tolerance is? Well here’s a clue. It’s not anywhere in those numbers that were posted.

18

I do not know what acceptable tolerance is. Are weekend warrior, casual plinkers required to know gas port tolerances and engineering specs?