SUB2000 Stock Rear Sight Mod for Skinner Apertures

My Kel-Tec SUB2000 is brand new. It was a surprise Christmas gift from my wife. It was a surprise, because it wasn’t a gun that was on my “radar.” But right away, I fell in love with it. The ability to fold is just “really neat!” It can easily fit into a laptop case or backpack. Very portable!

The day after Christmas, I “christened” the SUB2000 (aka “S2K”) at the range. Right away I was reminded of my aging eyes’ diminishing ability to focus on the front sight of a gun. On top of that, the AR-15 A2 style front sight post is black with a black rear peep sight. My target was mostly black, too! So, I was working with a fuzzy and black front sight on a black target background. No bueno!

My targets were still decent. But the OCD in me wants better.

Back at home from the range I began researching a “red dot” sight for the gun. However, the S2K’s folding feature would be prevented by a sight affixed to the top rail. I discovered a number of Rube Goldbergian gizmos designed to work around this issue and allow the rifle to fold for compact storage and carry. One gizmo (from M*Carbo) I found was particularly clever and appears to be of very high quality. It flips out of the way and to the side, allowing the S2K to fold. And I may end up getting it.

However, there is something I find attractive about the clean lines of the S2K when it’s folded. Maybe there’s a way to improve the iron sight picture for my older eyes.

I was reminded of my Browning BL-22, on which I have Skinner’s venerated peep sight. It has interchangeable apertures for various lighting conditions and / or desire for more precision.

I wanted to take advantage of the optical science of using a smaller aperture. Just like with a camera, a smaller aperture increases the “depth of field,” bringing close and far objects into simultaneous focus. This would sharpen the front sight for my presbyopic eyes. The downside of a smaller aperture is that it decreases the amount of light transmitted. So, it’s applicable to environments with a high level of ambient light and bullseye / precision shooting. For defensive and low light conditions, a larger aperture is preferrable. For the largest opening, I can just unscrew the aperture and use the sight without an insert.

The S2K’s rear peep sight is made of plastic.

What if I could drill and tap it to accept the Skinner Sight apertures? Skinner’s aperture webpage says, “Our apertures are threaded 12-40 and will fit most other manufactures 7/32-40 sight mounts.” So, I went online and found a source for a 7/32-40 tap and corresponding #9 drill bit.

Before I would permanently modify the sight on my S2K, I wanted to do a practice run. I happen to have a sheet of Nylon that I bought to test tools on before I use them on my Polymer80 projects. I drilled a hole and then used the tap. It worked perfectly!

I’ve had my Kel-Tec SUB2000 for only 4 days, and I’m going to start whacking on it?? I must be crazy!

So, I went to work on my S2K’s rear sight. I enlarged the stock peep sight hole with the #9 drill bit, which was very easy. The plastic is quite soft.

Next, I ran the 7/32-40 tap through the new, wider hole.

Next, I tried in the Skinner aperture. Booya! It worked! Screwed right in!

​ But did it REALLY work? Let’s try to fold the S2K. Rut-roh. Crap! It’s too thick. It won’t close. I’ve GOT to be able to fold my folding rifle!

OK. I’ve got it! The stock rear sight is fairly thick. I can countersink the Skinner aperture, right? I’m pretty handy “machining” plastic with all my P80 building experience! And I’ve got all manner of Dremel tools, including a collection of diamond bits in various shapes. I mounted the rifle on an “Ergo Mast” so I’d have both hand free to guide the Dremel carefully, using “finger rests.”

Steady as she goes!

The S2k rear sight has a handy molding seam that tells you where the middle is. That would conveniently mark the limit of my countersink grind.

The secret to machining plastic is to go SLOWLY. I mean REALLY slowly! Super slow! I’m not talking about the Dremel speed. I’m talking about the pace at which you make your cuts or grinds. Use a light touch! Do a little and inspect. Do a little more. Rinse and repeat.

OK… That looks good! Kinda! Besides needing to clean up the plastic “fuzzies,” the problem is the aperture screw sticks out the other side. So, it’s still too thick and prevents the S2K from closing!

OK… Time to grind off that excess screw. Maybe then it will be thin enough to fit and allow the S2K to fold.

Done! That looks better!

But will it fold and lock? Success!

So, at least now I have options for the rear sight. I can screw in a smaller aperture for bullseye / precision shooting at the range. If I want to practice defensive shooting, I can switch to a larger aperture or remove the aperture altogether. Or I can use one of the aperture sizes in between. Whichever works best.

These peep sight apertures are available at Skinner Sights. Here’s a screenshot of their recommendations for aperture sizes:

I hope you found this write-up helpful or at least thought-provoking.


If ALL ELSE FAILS ?!? THROW the gun at them. 200YDS away

DUDE you are a breath of ///// freashness :crazy_face: :crazy_face: :crazy_face: :crazy_face: :crazy_face:

So when are you cutting off the flippong legs ???

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Try notching the original for quicker accusition. Leaving the bottom stays oncenter.

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