I recently purchased a DOE front sight and handguards, but I've seen photos floating around of people with DOE set-ups, but in 5.56. I know that involves drilling the FSB for a gas port, and additionally, I'd have to have an existing pistol-length barrel re-contoured (or a lightweight longer barrel chopped) to fit the DOE endcap and FSB diameter.

Is there anyone that's done this and/or has a recommendation for someone who can do this? This is definitely out of my realm of technical skills.

I'd give John Thomas at Retro Arms Works a shout & see if he can do this.  John can do almost anything AR related.  [email protected]

I'd rather keep it a 9mm build, but that being said I don't think you would need to drill the DOE front sight for a gas port, and honestly I don't think you would have much success with how little material is there and the complete lack of dwell time with the front sight being right out on the muzzle. If you insisted on using the front sight as the gas block (and I really don't think you have enough material to work with) you might be able to use a LaFrance M16K style gas tube setup.

I think that there is likely enough room under the handguard and behind the front sight to run a pistol length gas system with a lowpro gas block.

*edit I would run this barrel https://www.kakindustry.com/ar-15-parts/upper-parts/barrels/5-56-mm/8-0-inch/contract-556-8-inch-pistol-melonite-barrel the only machining required is cutting it to the right length and turning down the end for the DOE sight. Easy.

Is there room for a pistol length gas tube in behind the FSB?

Doing one in .300 Blackout might be pretty cool and is somewhat in keeping with the concept.

Did it, and it runs great.

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Still on the hunt for an N1 stock that isn't the price of being raped with sandpaper

Details on the build?

Where to find DOE parts?

I'd be interested in what it looks like under the handguards—do you have a low profile gas block under the handguards or are you using the DOE FSB?

I paid for the N1 and loved it... then I needed more.

Turns out the M&A is a VERY acceptable substitute. Even though I don't move stocks around a lot, I still always check for the code before I take the M&A out for some banging around.

I had been thinking of doing a 5.56mm DOE gun for years. I always liked the DOE format, but I never cared for the 9mm AR15, SMG or semi-auto. Once I had my first SBR lower, I had no reason not to do the upper.

I purchased the front sight assembly and handguards from Sherluk at Knob Creek. I believe these are Garrison parts, but I'm not positive.
The handguard is the one piece Delrin unit, and the metal parts are pretty much a faithful copy of the Colt parts. While I would have preferred the original DOE/M231 two-piece handguards, the delrin ones are high quality and allow for a lot more room underneath for the plumbing that Colt never had to consider for the DOE gun. The metal parts are OK, but I did re-cut the detent notches on the folding front sight and make a plunger to replace the ball bearing for the detent. I also used a precision ground pin to replace the spring pin as a pivot. All of this was not absolutely necessary, but did improve the feel of the sight.

I had a Bushmaster chrome-lined 1/9" M4 barrel that I'd used with good results over the years. I'm not a Bushmaster fan, but this barrel not only shot very well, it was always 100% reliable and headspaced dead on with a Colt bolt, so it was donated to the project.

The gas system was designed to take advantage of the high port pressure available while trying to mitigate the short dwell time. Looking at the DOE front sight, it didn't seem a good choice to be the gas block too, since the muzzle is only 0.340" from the front of the sight. I ended up using the smallest gas block I could find and attaching a "pigtail" pistol length gas tube under the handguards. This allowed the gas port to be ~2.150" behind the muzzle, and provides plenty of dwell time. The pigtail gas tube seems to smooth out the gas impulse compared to a straight pistol tube.

I range tested the gas port diameter starting at 0.051" and increasing the size until I achieved reliable function. I believe it ended up being 0.072", but I'm not 100% sure about it, but that sounds correct. I had 8 different diameters between 0.051" and 0.080", and it looks like I stopped at 0.072". Here's the gas layout-



It's run 100% with a variety of ammo both on my Noveske SBR lower with the A5 buffer system, my Colt SBR lower with the standard "H" buffer, and even full-auto on an M16 lower.

I have more dimensions if someone needs them, but that's the basics.
BTW- I prefer it on the more original/traditional Colt lower.

Ah that makes a lot of sense. I wasn't sure if there'd be enough room under the handguards but before the DOE FSB for a low profile gas block but indeed you've done it. Makes sense, especially when you consider there's very little of the barrel sticking out after the FSB anyway.

Postino made a few .223 DOE uppers a few years ago, but he has since retired...