DIY Kel-Tec CMR-30 Rail Extension

CMR 30 extended HG marked

Last Halloween I managed to pick up a Kel-Tec CMR-30 during my first ever trip to Grice’s Gun Shop. I was in the area for a 2Gun match in Mifflin County and decided to finally visit the famous store. They had one CMR-30 in stock so I swooped it up. On the 2 hour return trip home I started thinking of ways to modify the CMR-30. I knew I didn’t want to SBR it. In fact I wanted to cover up the barrel. Upon looking at the exploded diagram in the CMR-30 manual, I figured out a simple DIY solution to making a rail extension. The only problem would be getting the spare parts from Kel-Tec.

CMR-30 parts

I reached out to the Customer Service Manager that helped tune up my KSG when I was down in Florida for Big 3 East back in early October. Sean Turpin helped me get most of the parts I needed. The parts list is small but CMR-30s are in high demand so spare parts are scarce. I was lucky to get what I did. Here are the parts I needed:

1x Extruded Top Cover
1x Extruded Bottom Cover
2x Barrel Blocks
2x Bottom Rail
4x short screws
4x long screws

I got everything except the two extra barrel blocks. That put my project on hold, they did not have any to spare. I waited hoping they would be back in stock. Unfortunately they weren’t so I asked my friend Brian Miller for help. He is the one who made his own muzzle brake for his new 3Gun project Vepr12. Anyway I sent him a picture of the barrel block and he said he could make it with his mill.

IMG_8364

 

My concept was to cut down the extruded top cover to the same length as the bottom rail and cover. Then drill new holes for barrel blocks at each end. Next I would slide this extension over the barrel and bolt the rear barrel block to the block already on the gun. It would not be free floating but that is fine for what I will use this for.

We tried to use my friend’s CNC Mill but it has been a while since he used it so we decided to just make the barrel block with the manual mill.

IMG_8371

Brian has a 10 ft long piece of 3/4″ thick aluminum. He cut off a piece of it and we traced the factory barrel block onto the raw brick of aluminum. The he cut the barrel block out of the aluminum with his mill.

You can see below the raw aluminum barrel block he made is wide enough to bridge the seam between the two rails. Next up we had to drill and tap the holes for 6-32 screws.IMG_8374

IMG_8386

 

The next step involved using a metal band saw to cut down the extruded covers. Originally I thought it would be easy to use the bottom cover length as the length of the extension. That way I only have to cut the top cover once. However this would make the rail extension too long and cover up the threaded barrel. The inner width of the handguard is too narrow to fit a flash hider, so the threads would have to protrude out the front. Another issue is the slot for the charging handle. If cut the rail only once, then the cut will go across the charging handle slot and I would not be able to screw the rail to the sides of the barrel block. So we had to make two cuts and we milled them to make sure they were flat.

IMG_8382

 

The final step was to cut down the two bottom rails to the right length. One will go on the top cover and the other will go onto the bottom cover.  Then we had to drill and countersink the holes for the 6-32 screws that will hold them to the barrel blocks.

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Here is the fruit of our labors.

IMG_8392

 

And here it is with a couple of accessories. I may remove the bottom rails. Grabbing the extension without a bottom rail is surprisingly comfortable and will eliminate the need for the AFG.

IMG_8405 IMG_8410



Nicholas C

Co-Founder of KRISSTALK forums, an owner’s support group and all things KRISS Vector related. Nick found his passion through competitive shooting while living in NY. He participates in USPSA and 3Gun. He loves all things that shoots and flashlights. Really really bright flashlights.

Any questions please email him at nicholas.c@staff.thefirearmblog.com


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  • Twilight sparkle

    Spare parts available for a vapourware gun… interesting.

    • Edeco

      Strange. I’ve read I think on ktog about them doing barrel switches on the RFB as well.

    • Nicholas Chen

      Vaporware is not accurate since the CMR-30 is out an people have it in their hands. Some of SureFire lights and Crye’s Six12 shotgun is Vaporware.

      • Hensley Beuron Garlington

        Mmm…
        Crye’s SIX12 vaporware gets me high. That and the Desert Tech MDR are like my favorite vaporware addictions right now. I have a problem.

      • Kyle

        I had forgotten about the Six12 completely. Hahaha I even put my email in for updates about it long ago too. Pity, it was a really neat concept.

      • Twilight sparkle

        I still haven’t seen one at any of the places I frequent

        • Nicholas Chen

          Look outside the places your frequent then. Sadly many of them seem to just end up on Gun Broker. There are several right now.

          • Twilight sparkle

            I live near a cabelas and a gander mountain and I frequent multiple local places too, either I have really bad timing (which isn’t unlikely knowing me) or they just aren’t out there that much.

  • thedonn007

    Is the second barrel block touching the barrel? Did it affect accuracy or change the POI?

    • Nicholas Chen

      Not really the factory barrel block hole ID 0.648 inches. The barrel OD is 0.625″

  • Kovacs Jeno

    Great Job! (it should be a factory option)

    • Anonymoose

      I’d rather have a factory CMR-30 SBR. It would be about as close as we’re ever going to get to a civilian-legal MP7.

      • Sianmink

        .22Mag seems to perform best out of a 14 inch barrel. I don’t think I’d want to shorten much past that.

      • LV-426

        DAT 4.6mm tho!! :]

  • noob

    That’s beautiful. I wish they’d extrude the tops and bottoms in one piece as an optional upgrade but what you’ve done looks just as good.

  • EGS

    If the stock were an underfolder, the CMR would take on a more major movie franchise (SW) appearance

    • Nicholas Chen

      I suppose if you squint maybe. I have a Sterling MK4 and they don’t looks the same.

  • smartacus

    i wouldn’t mind a 9″ barrel for my PMR-30

  • Billy

    Who cares about the rail? I think it’s more impressive that somebody actually bought a CMR-30. I didn’t even know Keltec released it. Did they sell one by accident?

  • janklow

    not a great fan of the base gun… but that looks like an excellent addition. fine work.