New Project: .50 BMG Sniper

[buffalowinter]

A year or two ago I picked up a surplus McMillan TAC-50 stock because...well, because who knows when you'll need a McMillan TAC-50 stock. Anyway, I got a pretty good deal on an Armalite AR-50.

It's a pretty nice gun in and of itself, but I might as well put the McMillan stock to use.

So now I have to cram this

Into this

So that it ends up something like this

The magazine is going to be basically a cartridge storage box and fill the void in the stock. There's not enough metal in the Armalite action to mill a cut for the magazine to make it a repeater. I've got a pretty good plan figured out and it shouldn't be too difficult. Make some recessed steel pillar bedding blocks, bed the whole thing, and make the appropriate bottom metal with a trigger guard and magazine. I'm going to reinforce the stock with steel inserts. I must resist the temptation to build a recoilling hydraulic buffer system that I've been thinking about.

And I can always SBR it.

 

[diverdon]

Why when you say "recoiling hydraulic buffer system" am I reminded of:

 

[buffalowinter]

Why when you say "recoiling hydraulic buffer system" am I reminded of:

you should be reminded of this

 

[buffalowinter]

First recessed recoil lug finished.

 

[USMCSGT0331]

Awesome thread, I'm looking forward to seeing your rifle when it's done! I also have an original Navy SEAL used Mk15 Mod 0 stock kit, but I don't think I'll ever build it. If I were to build it, I'd need to find an older McMillan Bros receiver with the old style receiver screw spacing and BMG serial number prefix. The current McMillan receivers have a different screw hole spacing, so it would take a bit of work to have the stock re-inletted for the current screw spacing (and it would probably mess with the fixed magazine).

 

[buffalowinter]

Awesome thread, I'm looking forward to seeing your rifle when it's done! I also have an original Navy SEAL used Mk15 Mod 0 stock kit, but I don't think I'll ever build it. If I were to build it, I'd need to find an older McMillan Bros receiver with the old style receiver screw spacing and BMG serial number prefix. The current McMillan receivers have a different screw hole spacing, so it would take a bit of work to have the stock re-inletted for the current screw spacing (and it would probably mess with the fixed magazine).

Yeah, I got the rear action screw to line up as that is the least amount of work when re-bedding. That way the trigger lines up. the trigger is the critical dimension. The action can't sit too high or too low. I did one gun where the trigger sat really high so that it didn't clear the bottom of the stock. I cut the trigger off and made a new extended trigger to clear the stock. That actually gave a really nice trigger pull because it was a long lever and cut the trigger pull weight in half. I fill the forward empty receiver hole in the stock with a metal bar and bed it and then drill a new hole for the new forward action screw and pillar. You should definitely finish that. I saw a TAC-50 go for over 10K and who knows what one's worth now.

 

[buffalowinter]

Finished hogging out the stock. The way I'll bed this is in 3 or 4 parts, especially with a 32 pound barrelled action. First I just bed the pillars with tape and clay supporting the barrel and making sure everything is oriented and square. Once the pillars are bedded, I'll bed the rest of the action. I'll bed the whole action and the 3 inches or so of barrel. The barrel is probably too heavy to free float. I always bed the first inch or so of the barrel and if accuracy is not up to par I go back and simply remove some bedding around the barrel to free float it. Lastly, I'll go back and bed a steel stiffening plate in the magazine well.

 

[buffalowinter]

Bedding the pillars

 

[roostercogburn98]

Another cool project. Thanks for sharing

 

[buffalowinter]

Steel reinforcing plate bedded.

 

[gm9658]

whos Suppressor did they use
i May have one like new

 

[buffalowinter]

whos Suppressor did they use
i May have one like new

If you're asking about the guy in the top pic, it's just a photo I grabbed off the internet. Upon closer inspection, that's a McMillan stock but not a TAC-50...it may be a 338LM or some type of Chey-Tac.

 

[Forgetful Coyote]

Bedding the pillarsView attachment 7894713

Very cool @buffalowinter .. did you teach yourself how to pillar bed?

 

[gm9658]

If you're asking about the guy in the top pic, it's just a photo I grabbed off the internet. Upon closer inspection, that's a McMillan stock but not a TAC-50...it may be a 338LM or some type of Chey-Tac.

I was just wondering if you were going to put a can on it

 

[buffalowinter]

I was just wondering if you were going to put a can on it

No plans for a can, since the ATF is all over the place on Form 1 cans, otherwise I might have built one just for the hell of it.

Glass bedding

 

[KillerK]

whos Suppressor did they use
i May have one like new

I think they used a Reflex suppressor from BR Tuote

 

[buffalowinter]

Very cool @buffalowinter .. did you teach yourself how to pillar bed?

Pretty much. Commercial pillars like Brownell's come with instructions, but everyone pretty much has their own method. I use both aluminum and steel pre-made pillars, or in this case, machine them out of steel bar. I hog out the stock and set up shims with tape to get the barreled action where I want it and then bed only the pillars. Once the pillars are bedded, I bed the rest of the action. I usually only bed the action, unless the barrel is very heavy. Then I bed part of the barrel and can go back and open up the barrel channel if accuracy isn't up to snuff.

 

[camocorvette]

Always a great thread by you. Thanks for bringing us along on another great build. That's gonna be a beast!

 

[buffalowinter]

Pretty much done. Waiting for a trigger guard/magazine latch. Went with an AK-47 trigger guard with integral magazine latch...$18

Bedding done

Complete rifle less trigger guard.

 

[tomcatmv]

Pretty much done. Waiting for a trigger guard/magazine latch. Went with an AK-47 trigger guard with integral magazine latch...$18

Bedding done
View attachment 7896241


Complete rifle less trigger guard.View attachment 7896242

View attachment 7896243

View attachment 7896244

View attachment 7896245

Awesome!! What glass you gonna mount?

 

[Forgetful Coyote]

Pretty much done. Waiting for a trigger guard/magazine latch. Went with an AK-47 trigger guard with integral magazine latch...$18

Bedding done
View attachment 7896241


Complete rifle less trigger guard.View attachment 7896242

View attachment 7896243

View attachment 7896244

View attachment 7896245

Very interesting. What loads do you plan to run? Any access to Raufoss rounds?

 

[Longrangeprecision762]

When is the King of 2 Mile again

 

[buffalowinter]

I bought a complete reloading set for .50 bmg. It was like $218...after checking all the prices you basically got a press for free with all the dies, shell holders etc in lieu of purchasing all the dies, shell holders etc separately. Bad news is, reloading supplies, like primers and bullets, are shamelessly over priced...over $399 plus hazmat shipping for 500 primers. Bullets are just as bad. With prices like that it is cheaper to buy factory or surplus ammo. I found some PPU Match for around $4.50 a round and some Latvian new manufacture ammo for about the same. Euro ammo is pretty good because it is all ISO certified. As for glass, I can always use one of my Nightforce's, I have a Leupold LRT my wife isn't using, and right now I put an old Springfield Armory 6-20 x 56mm scope on it. The trigger is a little heavy for my taste. I'm thinking of cutting the curved trigger off and putting a straight trigger bar on it. By putting your finger at the bottom of the bar, you have a lever and cut the perceived weight, albeit at the cost of trigger travel. That's a pretty cool concept that I've seen in Hammerli triggers and was used on the Swiss STG 57 battle rifle. That has a really long lever, probably for winter use with mittens, but I've seen match shooters use it because it gives a much better trigger feel.

Swiss match shooter using the long trigger bar.

The long trigger bar in the un-extended position at the front of, and above, the trigger guard.

 

[Forgetful Coyote]

I bought a complete reloading set for .50 bmg. It was like $218...after checking all the prices you basically got a press for free with all the dies, shell holders etc in lieu of purchasing all the dies, shell holders etc separately. Bad news is, reloading supplies, like primers and bullets, are shamelessly over priced...over $399 plus hazmat shipping for 500 primers. Bullets are just as bad. With prices like that it is cheaper to buy factory or surplus ammo. I found some PPU Match for around $4.50 a round and some Latvian new manufacture ammo for about the same. Euro ammo is pretty good because it is all ISO certified. As for glass, I can lways use one of my Nightforce's, I have a Leupold LRT my wife isn't using, and right now I put an old Springfield Armory 6-20 x 56mm scope on it. The trigger is a little heavy for my taste. I'm thinking of cutting the curved trigger off and putting a straight trigger bar on it. By putting your finger at the bottom of the bar, you have a lever and cut the perceived weight, albeit at the cost of trigger travel. That's a pretty cool concept that I've seen in Hammerli triggers and was used on the Swiss STG 57 battle rifle. That has a really long lever, probably for winter use with mittens, but I've seen match shooters use it because it gives a much better trigger feel.

Swiss match shooter using the long trigger bar.

The long trigger bar in the un-extended position at the front of, and above, the trigger guard.
View attachment 7896422

Have you ever shot any of the SIG 550 series rifles? Impressions?

 

[buffalowinter]

Have you ever shot any of the SIG 550 series rifles? Impressions?

I have a SIG 551. It's a nice gun but it doesn't do anything an M4 can't do and the M4/AR-15 can do a lot more that the Sig.

 

[buffalowinter]

Correction on the scope. It is a Springfield Armory Government 10x56. I'm looking for a Unertl MST-100 .50 cal in the $2.5K price range if anyone has one. I'll be checking the CMP auction site.

 

[towerofpower93]

Correction on the scope. It is a Springfield Armory Government 10x56. I'm looking for a Unertl MST-100 .50 cal in the $2.5K price range if anyone has one. I'll be checking the CMP auction site.

View attachment 7896497

Do you have a desire to adopt a 39yo vet who has a loving wife and an almost 4yo daughter, haha?

 

[roostercogburn98]

Bad news is, reloading supplies, like primers and bullets, are shamelessly over priced..

Too bad you didn’t post this thread a few weeks earlier. I just sold all my 50bmg reloading stuff fairly cheap.

 

[buffalowinter]

Do you have a desire to adopt a 39yo vet who has a loving wife and an almost 4yo daughter, haha?

Sure, I can always use a couple more family to help around the ranch.

 

[VJJPunisher]

Always a pleasure to read through your builds

 

[buffalowinter]

Always a pleasure to read through your builds

Yours too.

 

[Sureshot300norma]

Awesome thread, I'm looking forward to seeing your rifle when it's done! I also have an original Navy SEAL used Mk15 Mod 0 stock kit, but I don't think I'll ever build it. If I were to build it, I'd need to find an older McMillan Bros receiver with the old style receiver screw spacing and BMG serial number prefix. The current McMillan receivers have a different screw hole spacing, so it would take a bit of work to have the stock re-inletted for the current screw spacing (and it would probably mess with the fixed magazine).

 

[Sureshot300norma]

Want to get rid of the rail or all of it,let me know.

 

[huggybearuno]

Finished hogging out the stock. The way I'll bed this is in 3 or 4 parts, especially with a 32 pound barrelled action. First I just bed the pillars with tape and clay supporting the barrel and making sure everything is oriented and square. Once the pillars are bedded, I'll bed the rest of the action. I'll bed the whole action and the 3 inches or so of barrel. The barrel is probably too heavy to free float. I always bed the first inch or so of the barrel and if accuracy is not up to par I go back and simply remove some bedding around the barrel to free float it. Lastly, I'll go back and bed a steel stiffening plate in the magazine well.

View attachment 7894642

View attachment 7894643


View attachment 7894644

Why would the AR-50 barrel be too heavy to "free float?" With the original action/stock, it comes free floated from the factory. At least MINE did/is.

 

[towerofpower93]

Sure, I can always use a couple more family to help around the ranch.

My daughter is much cuter than any of those mine urchins

Looking forward to the range report.

I have a desire to get a .50, just because, but the knowledge that I'd be spending just as much on reloading shit as I did on the rifle before I even break the first shot has stopped my "buy now" trigger finger a few times.

 

[buffalowinter]

Why would the AR-50 barrel be too heavy to "free float?" With the original action/stock, it comes free floated from the factory. At least MINE did/is.

It's just how I was taught by Neal Johnson who was a pre-eminent Olympic riflesmith and led the way in fiberglass riflestocks in the 1970's. He liked to support the first inch or so of heavy target barrels. I always do this because it is easy to go back and free-float this portion if accuracy isn't satisfactory. Fiberglass is far more susceptiple to impact damage than aluminum and hanging a 30 inch barrel off of a fiberglass stock supported only by the bedded receiver could be a problem.

 

[TapRackBang]

very cool build and write up appreciate you sharing it.

 

[BullGear]

Thanks for taking us along, this build is amazing.

Congrats!

 

[shoots100]

Nice looking rifle.
When I first saw your post, I thought you were going to make a mag fed AR50.

 

[buffalowinter]

Nice looking rifle.
When I first saw your post, I thought you were going to make a mag fed AR50.

I don't feel there is enough metal in the action to make it into a repeater. Cutting a magazine slot would really weaken the action.

 

[shoots100]

The AR receiver is bigger than the McMillan receiver.
Look at how much material you had to cut out of the Tac50 stock to inlet the AR receiver.

 

[buffalowinter]

The McMillan action is round and has far more surface in the magazine area than the hexagonal Armalite. The Armalite has what is basically a stiffening rib running down the bottom center that would have to be removed for a magazine cut. I'm pretty sure that a cylinder under compression with a magazine cut versus an hexagon with a similar cut will fair far better under compression. At 3k I don't see a need to experiment.

 

[viking78]

I think they used a Reflex suppressor from BR Tuote

Reflex Suppressors for .50 cal. rifles

BR-tuote was the oldest Finnish suppressor mass manufacturer, but this company is over now.

 

[buffalowinter]

The AR receiver is bigger than the McMillan receiver.
Look at how much material you had to cut out of the Tac50 stock to inlet the AR receiver.

And after a little research, I confirmed that a cylindrical tube is much stronger under compression than a hexagonal tube.

An additional factor is that any section which has defined corners will tend to concentrate stress at the corners rather than it being evenly distributed throughout the section.

With tubing this can be a double effect that you potentially have work hardening from the manufacturing process concentrated at the corners as well. If the section has a uniform wall thickness then it certainly means that some of the material is effectively wasted as the corners will encounter yield before the flats and at worst it can lead to crack propagation points and fatigue.

It is a fairly good rule of thumb in structures that any sort of discontinuity represents at best an inefficiency and at worst a potential failure point. An ideal structure will have a smoothly varying section with section size proportional to the stresses on it, in fact bones are an excellent example of this. Although this is, in most cases, impractical for fabricated frame structures.

frame.structures.https://engineering.stackexchange.com/

 

[shoots100]

I guess that's why they never made a mag fed Ar50.

 

[sirhrmechanic]

I guess that's why they never made a mag fed Ar50.

Surprised Serbu didn’t add a mag!

Sirhr

 

[buffalowinter]

Got the ak-47 trigger guard today...it's like it'smade for the TAC-50...don't need to change a thing. 4 epoxied screws, some paint, and I cut a groove in the magazine for the latch.

 

[towerofpower93]

Got the ak-47 trigger guard today...it's like it'smade for the TAC-50...don't need to change a thing. 4 epoxied screws, some paint, and I cut a groove in the magazine for the latch.
View attachment 7900777

Cool. Now go shoot something, like a cinder block, or a car, or a satellite!

 

[iceng]

Or the cinder block behind the car, which is orbiting a satellite

 

[buffalowinter]

Had to make a new cheekpiece extension due to the tiny McMillan Cheek piece and huge AR50 bolt.