50 BMG project

[mitch260]

Thanks for responding I am making the action out of 4130 that I am going to have heat treated after I am done machining. The bolt is 4140 that will be hardened as well.

As for the muzzle brake, I am not 100% sure. I am going to either use the J E custom brake or an Armalite, I may even make my own.

Here are a few pics of the progress so far, the barrel is ready to go as of today and the action and bolt are coming along nicely. I am waiting on a new rotory table for my mill to do most of the machining on the those pieces

 

[MudRunner2005]

Pictures??? I must be getting that Ray Charles disease...



Just messin with you Mitch. I'm still interested in seeing this come along. Did you ever get your manufacturing FFL? If it's that cheap to build one, I'd still love to have one.

 

[mitch260]

Sorry, I had 3 pictures attached but I must have done it wrong, I'll try again later.

Sorry about the FFl too, I don't think its in the cards for a few years

By the time I'm done I should have less than $500 dollars into it, but it takes me a lot of time because I don't have all of the fancy CNC stuff yet. I'm really itching to pull the trigger though!

 

[mitch260]

I cant figure out how to post pictures. Can any one tell me how?

 

[MudRunner2005]

Make a Photobucket account (it's free), and post the image

 

[mitch260]

 

[MudRunner2005]

I'm interested to see which direction you go with it, because I see lots of different options for stocks ideas, triggers, bolt designs, etc... Are you gonna make the bolt a shellholder style that holds the back of the case, and when you pull the bolt out the shell comes with it?

What kind of trigger setup are you gonna use? Remington 700?

 

[mitch260]

I am planning on making a stock similar to the Noreen ULR and Cheytac/EDM stocks, with a tube hand-guard so that I can shoot off of a rest or sand bags and not just a bi-pod. I may end up with a McMillan Big Mac eventually though(or maybe if I do another one in .416 Barrett or .50 Improved).

As for the trigger I am just going to use a mauser 98 trigger because they are reasonably priced (the one I got was only $50) and have work very well for me on past builds.

And yes, it is going to be a shell holder style bolt. Its going to be a little different than most shell holder designs in that the extractors will be separate pieces that are bolted on. I haven't decided if I'm going to make it a 2 or 3 lug design.

I'm getting really excited

 

[bruce_ventura]

Mitch, This thread is making me a little nervous because I'm not hearing you talk about the design margin in the bolt/receiver or the bolt design.

I shoot 50 BMG for work using some pretty heavy rounds. I would not get behind a custom rifle unless I knew it was designed with safety as a top priority. I rely on very good ballistics people to develop and test the loads that I shoot. After talking to the designer of my test rifle, I'm convinced the receiver and bolt have good design margins. The gun has been independently tested to insure it can't fire out of battery. After 100's of heavy rounds, the gun is showing no visible wear.

I would expect the bolt to prevent the hammer from contacting the firing pin unless the bolt was at least half-way closed. I'm no engineer, but I would expect an adequate receiver design to withstand about 50,000 lbs of force on the bolt in any bolt position for which the hammer can contact the firing pin That's for a 2X design margin on the 65,000 psi internal pressure for a hot 50 BMG load.

You've done all your homework on this receiver design, right?

 

[mitch260]

Bruce,

I have/am designed/designing all of my parts on Solidworks and have run stress tests on all of the critical components, and have made sure there is plenty of extra material. And the first 20 rounds or so will be fired with the rifle strapped to the bench and inspected after each round.

Also, the rifle will not be able to go off unless the bolt is closed completely.

I understand your concerns as the .50 BMG is a large cartridge with a lot of bolt thrust, and I've also read some of the horror story's of shell holder type actions failing.

Thanks for replying.

 

[bruce_ventura]

That's reassuring. Good luck.

 

[mitch260]

Thank you.

I plan on updating this thread periodically as I get parts finished and start making something that resembles a riflegun)

 

[mitch260]

Unfortunately not long after my last post, this project got set on a back burner. I still haven't gotten a new rotary table for my mill and I've been working on some simpler projects. I also shoot a lot of F-class in the summer so that takes up a lot of my time. I still plan on finishing it up relatively soon, hopefully this winter. I will continue updating this thread once I get more of the parts finished.

 

[mitch260]

Hey guys, putting up an over-due update. Needless to say this is taking a lot longer than I had planned, just have a lot going on. It is still chugging along though, it will get finished eventually!

I do have some pictures in this update however. I have the lugs cut in the bolt which was my biggest challenge so far and the main reason this has been drug out as long as it has. I had some access to a HAAS CNC Mill for a while and took advantage of the opportunity to move this thing along.



I decided to go with a 3-Lug design for added strength.

The next picture I have for you is of a part that's not really necessary, but I think it will be a really cool addition to this rifle. I designed an adjustable scope base.





It has 6 settings from 0 to 300 MOA in 60 MOA increments (zero will actually be a 30 MOA rail). By going with this design, I was able to use dowel pins in precision reamed holes. This thing is very solid, should be interesting once I finally get the rifle finished and out pushing the distance. I am getting a SWFA 16x42 mil-quad scope (I know, its a mil scope on an MOA base) for this rifle so the scope can handle the 60 MOA increments with room to spare. Everything considered (base, scope internal, and reticle) I will have around 400 MOA total adjustment (depending on where I start looking through my muzzle brake). If you run the numbers, that gets you a dang-long-way with a 750 AMAX at around 2700 FPS, like beyond 4,500 yards. And that's even figured with my lowly 800 ft altitude atmospherics. Needless to say, I shouldn't run out of elvevation any time soon. Honestly, I will probably need a better barrel before it will group good enough to even mess with distances to a mile and more.gun)

Again, thanks for reading