Getting rid of the massive thumb nuts on the ACOG mounting base. An Ambidextral Gunfighter Improvise, Adapt, and Overcome project.

Big ACOG mounting nuts obstruct ambidextrous operations.
Castrating the ACOG

ACOG Big Nuts

The ACOG has big nuts that impede the ambidextral gunfighter when working with controls on the left side.

On my AR, I gave this obnoxious behavior a pass. But on the perfectly mirrored Desert Tech MDR, the deficiency stood out in stark contrast to the perfect ambi mirroring of the MDR.

The problem is that it is easy to snag a knuckle (overhanded) or break a fingernail (underhanded) with these protrusions. It disturbs the perfect mirroring Zen flow of the Desert Tech’s ambi controls.

While practice mag changes on the MDR, a knuckle caught one of the big, dangling Trijicon ACOG nuts, a brief spewing of vitriol, and that was it. A plan was afoot to castrate that ornery ACOG base.

Searched the internet for a replacement base. Trijicon had none. BoBro Engineering had some nice QD bases, Geissele has tight tolerance bases, etc. etc., but no one had a slim, unobtrusive, ambi mirrored base.

I learned that the nuts were 5mm and as I investigated, I discovered that quadcopters regularly use 5mm aluminium locknuts to secure props to the motor. My son, Broc, flies quads and sure enough he had a supply of the nuts on hand.

Will aluminium nuts suffice? One reason that Trijicon uses the big thumb nuts is to prevent users from over tightening them. You are supposed to tighten by hand and then add ¼ turn. Not exactly major torque. For tightening, aluminium should suffice. But will it survive 308 recoil? If not, steel nuts will replace them.

Using thin nuts with no thumb grip, we can cut off just over 3/10ths inch of the cross bolt stud. To make sure I do not cut too much, I insert a pic rail in the ACOG mount, place one of the nuts next to the stud and get a measurement of that amount of excess stud.

I use masking tape to mark the stud I want to retain and to protect the threads from damage.

Then we get serious. A Dremel with a cutting disc is assigned the task of castrating the ACOG. Trijicon uses quality steel, so it takes a bit of high speed Dremel work to shorten the studs.

After the studs are shortened, I polish up the ends to help make for clean threads. Then using one of the better, original thumb nuts, I clean up the steel threads. A tiny dab of anti-seize will help prevent steel-aluminium galvanic corrosion.

Then I placed the ACOG back on my Desert Tech MDR and threaded the little quadcopter nuts onto the mount. While pressing the mount toward the muzzle, a gentle tightening with small socket wrench secures the ACOG.

And now my hand is free to operate the left side charging handle without fear of snagging a knuckle or breaking a fingernail.

I would really like to countersink some flathead nuts to make the whole thing even more streamlined. The low profile nuts are a huge improvement over the big thumb nuts. I am confident my knuckles and fingernails are safe. And these nuts are far less likely to snag on sling webbing.

So...until someone comes up with a better solution...improvise, adapt, and overcome.

Free booklet, The Ambidextral Gunfighter
www.ambgun.com