Gunsmithing Homemade Picitinny Rail

[Macarms]

G'day all,
I have had some interest in the picitinny rail I just finished, so I thought I would do a DIY / How to / How I went about machining it. Just to show some pointers and lil tricks I used to machine it.

I started out with a piece of 7075 bar and rough machined it to size. I machined a step on one end after I machined the top section. To allow me to mount a weaver picitinny rail as a guide through the machining processes.

I drilled and tapped two 6 x 48 tpi torx screws through the weaver rail to securely mount it to the piece of flat bar. I then trimmed the bar to the size of the weaver rail.

I then machined an arbour to hold a 45 degree cutter in my collet chuck, allowing me to turn the cutter upside down to do the underside of the rail, the arbour was also used to cut the rail off later on in the build.
The 45 degree cutter gives a good surface finish and can remore material quickly.

Mac

 

[Macarms]

Re: Homemade Picitinny Rail

After I machined the top angles,I turned the cutter upside down to cut the underside.

After the angles matched the profile on the weaver rail, I used another boring bar to put a little bevel on the underside of the rail for clearance on the rings.

After I was happy with the profile I set about cutting the groves on the top I was planing on using the horizontal arbour with a slotting saw but I decided to just use an endmill because of the saving in set up time. I done some test cuts on the piece under the weaver rail to check if I was happy with the spacing. the cuts are 5mm wide, 3mm deep with a 5mm space between the slots.

Mac

 

[Macarms]

Re: Homemade Picitinny Rail

I then used the arbour I made to hold a slitting saw so I could cut the rail of the rest of the bar.

I was going to cut a custom tapered base on the rail, I decided to make a jig to make it easyer to set up and adjust it would also allow me to do similar jobs alot easyier and quicker in the future.
I used a piece of 40x40mm 6061 alloy and machined it down for the rail.

I then set up my head to cut the 45 degree slots, this was another method I was considering using to cut the 45 degree angle on the rail.

I checked the fit against the weaver rail and my own one.

Mac

 

[Macarms]

Re: Homemade Picitinny Rail

I then drilled and tapped 6mm caps head bolts x 4 through the side of the clamp.

Then when I want to put a custom taper on the base all I need to do is raise one end of the jig in the vice to match the angle on my universal protractor.
Using a Formula Sine A = R/DR where A equals the degree, minutes and seconds of the angle of the milling head offset, R equals the raduis of the cutter to be used and DR equals the desired raduis to be cut.
This formula allows you to get very very close to the radius of what ever reciever you have with out having the exact right cutter for your diameter.
I ran some test cuts in a piece of scrap to confirm the fit I wanted

Once I was happy with the fit I set up the rail in the jig and set the jig to have a taper of 30 MOA or half of a degree taper to allow my scope to be able to be used for longer shots. I used my universal protractor to set the angle of the jig and the milling head.

Mac

 

[Macarms]

Re: Homemade Picitinny Rail

I then cut the radius on the bottom of the rail base, note the change in depth of cut due to the taper.

after the raduis was cut I removed the rail from the jig turned it over and drilled and counter bored the screw holes I used the protractor to set the rail to the right taper for the screw holes also.

My Warne QD rings also fit the new rail better than they fit the factory weaver rail.

If you have any questions of would like to see a specific pic just ask I took numerous pics along the way. I hope that this can help someone out there or at least offer some form of a guide to anyone else attempting to make one, There are many ways to machine a rail, this seemed like the best way at the time with the gear I have. And I couldn't be more happy with how it turned out its a better fit than the factory rails and it has the taper I wanted which was not available off the shelf by any one.

Mac

 

[Macarms]

Re: Homemade Picitinny Rail

Here is the link to the build of the rifle this rail belongs too.

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=3202972

Mac

 

[Carolina Shooter]

Re: Homemade Picitinny Rail

Man, that is awesome work.

Just out of curiosity - now that you've been through the process and have your setup worked out and your jig made, how long do you think it would take you to make another?

 

[Some Day]

Re: Homemade Picitinny Rail

You did a sweet job on that

 

[Tactical22]

Re: Homemade Picitinny Rail

Awesome! Tagging for future reference.

 

[turbo54]

Re: Homemade Picitinny Rail

Makes one appreciate buying one for $50-150.

 

[2156SMK]

Re: Homemade Picitinny Rail

This might not be an issue, but there's actually a clearance cut under the bottom angle called-out in the picatinny print.
Many picatinny rings will need more clearance than your mount gives.
The warne rings don't need the clearance cut as they are more of a weaver spec than a picatinny spec.

http://www.biggerhammer.net/picatinny/

 

[Furtaker_.223]

Re: Homemade Picitinny Rail

Impressive. I wish I had this kind of talent.

 

[Muttt]

Re: Homemade Picitinny Rail

I'm planning to make a tripod mount for my rifle. I'm wanting to mount a piece that looks very similar to your jig on top of my tripod. That way, I can just slide my bottom rail into it and tighten it down. If you weren't on the other side of the globe, I'd ask you to make me one.

 

[Macarms]

Re: Homemade Picitinny Rail

I know of the clearance you speak of, I checked it against all the rings I had both for weaver rails and 1913 Rails those included rings made by S&B, Leupold, Nightforce and Warne which covers anything I will be putting the rifle. So I left it at that, I was also showing a tip on an easy way to set up and make the rails, by directly copying the profile of another rail in this case a weaver one.

Mac

 

[Macarms]

Re: Homemade Picitinny Rail

One of the slowest processes is getting the radius on the bottom to match if you dont have a cutter that exact shape. There are quicker methods of cutting the angles at that time that was the only tooling I had, so I made do with that as I couldnt afford anything better, I also made all the Nt30 arbours to hold the various HSS cutters in the pictures as I couldnt afford them eather. A double angle cutter is on my too buy list for the next one I make which will save alot of time. That Jig I made is only for cutting custom bases under the rail , it allows a good clamp to be had on the rail and uninhabited machining of the underside.

Mac

 

[mcfred]

Re: Homemade Picitinny Rail

Very nice. Thank you for sharing.

 

[Sean the Nailer]

Re: Homemade Picitinny Rail

Mac, good job.

I see that you used 7075 for the base, and 6061 for the holding jig. Why? Just because that is what you had available, or other reasons?

 

[Macarms]

Re: Homemade Picitinny Rail

7075 is stronger and more durable than 6061 so I chose it for the rail, and I just happened to have it in the right size. 6061 was all I had laying around for the jig, and it will do the job fine.


Mac

 

[ballistic1]

Re: Homemade Picitinny Rail

Thanks for posting the "How To" on your project..

Very informative, and your pictures were just as impressive and insightful as the work you did.. ++

Good Job!