CETME / Hk Screw mount rail.

[bladeworks123]

The laser was sick this last week, and I am setting around waiting on parts for it to arrive to get some jobs done. I have been kicking around in my mind how to do a screw on rail setup as an alternative to welding. Here's what I came up with. I used one of Turbos rails, and contoured the bottom slightly with a 3/4" diameter die grinder stone so it would fit a little lower and have more surface contact with the receiver. I then drilled and tapped a 10/24 hole in the mount. I then taper relieved the hole on the bottom of the mount with a 45 degree countersink. I drilled a 3/16 inch hole in the receiver. I then placed the mount on the receiver and used a 10/24 grade 8 flat head machine screw to tighten the mount onto the receiver and draw the receiver up tight into the countersunk relief on the bottom of the mount. That formed a countersunk relief on the inside of the receiver. I then took a grade 8 pan head machine screw and ground a 45 degree taper on it and ground the top off flat to make a screw with a low enough profile to fit inside the formed rib on the top of the receiver,,,, to get the screw head to fit flush with the inside of the receiver. It worked perfectly.... the bolt carrier passes right over the screw head with no contact whatsoever. Now to do three more, to finish up. I think when they are tightened down with a little red loctite they should hold just fine....

[Hoover 1]

Really Nice!!:thumbup:

Thanks,

Hoover

[jfowl31]

sweeeeeeet! Any reason for not just welding it? Being an unfinished rifle and everything, it seems like the ideal time to weld it up. It also seems like it might stiffen the receiver up some more too and make it more accurate.

I think if I were doing a flat build, I would weld on the rail and maybe the stiffeners on the sides to get it as rigid as possible.

This seems like an awesome solution for anyone who wants to take this off and on though.

[bladeworks123]

sweeeeeeet! Any reason for not just welding it? Being an unfinished rifle and everything, it seems like the ideal time to weld it up. It also seems like it might stiffen the receiver up some more too and make it more accurate.

I think if I were doing a flat build, I would weld on the rail and maybe the stiffeners on the sides to get it as rigid as possible.

This seems like an awesome solution for anyone who wants to take this off and on though.

I welded one on my Frankencetme build and I also think that's the best way if you are building from the ground up, but I was thinking about guys with no access to a welder or who didn't want to have to re-finish their rifle. Forming the countersink in the receiver and relieving the bottom of the rail is the trick to getting the screws to set deep enough to allow the bolt carrier to clear. I'm going to build a two piece die that you can either wack with a hammer or put in a press to form the countersinks. The nice part is that by countersinking the bottom of the rail also, it locks the rail onto the top of the receiver so it cant slide at all. And, if you wanted to, you could also use tapered head rivets from the inside and pien them over and file flush on top. Adding a little JB weld or acraglass under the rail when you tighten it down would make this just as stout as a weld on, without messing up the finish on a rifle. When I get done with the other screws I will post a pic of how the receiver looks on top and how the rail looks underneath.

[97th Signalman]

That looks like an inspired solution to a challenging problem...nice job. I would be interested to hear how it holds up inder fire.

[kmagnuss]

How can I get ahold of a rail like that? I'd like to weld one on too. Will my scope stay zeroed if I take it off and put it back in the same notches? Can you still use iron sights with the scope off?

Thanks. :)

-Mag

ps...I tried to search but I came up with nada.

[bladeworks123]

How can I get ahold of a rail like that? I'd like to weld one on too. Will my scope stay zeroed if I take it off and put it back in the same notches? Can you still use iron sights with the scope off?

Thanks. :)

-Mag

ps...I tried to search but I came up with nada.

Just send a PM to turbothis, he's a member here, he has a friend who makes them up for him,,,here's a link to the post

http://www.militaryfirearm.com/Forum/showthread.php?t=12273

Theoretically your scope will stay zeroed if nothing moves, and you mount it back in the same location. And these are low enough that they do not interfere with your iron sights. Here's the one I welded on my Frankencetme.