Single Shot 50 BMG

[lkydvl]

Picked this partially completed single shot 50 BMG receiver and barrel combo from a friend sometime back.

Was started by a "B. V. Mack" in "1957" as stamped on the bottom of the receiver.
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150331_194414_zps228ba565.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150331_194414_zps228ba565.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150331_194346_zps4e060ea6.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150331_194346_zps4e060ea6.jpg.html)

http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150331_194434_zps9a085b1a.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150331_194434_zps9a085b1a.jpg.html)

http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150331_194510_zps464f93ca.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150331_194510_zps464f93ca.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150401_185937_zps1e6fcfa4.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150401_185937_zps1e6fcfa4.jpg.html)

Took it to another smith friend of mine, with a complete shop thankfully, and we started a working it over.

Several issues we corrected were:

Extending the tang and bolt stop block so the attachment screw could be removed without disassembling the bolt while it was still in the receiver

Removing the plates that were made to house some unknown trigger assembly

Working out the placement and attachment of the new trigger

Modifying the trigger's sear by adding height to it so it reached the cocking piece

Fitting the sear, cocking piece and bolt stop for proper operation

Cleaning up welded areas of the tang and stiffener under the receiver

Properly locating and tapping holes for the stock bolts and upgrading their size from 1/4x28 to 3/8

Straightening the firing pin tip

As it looks now
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150523_103337_resized_zps4a6f22cd.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150523_103337_resized_zps4a6f22cd.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150523_103414_resized_zpse0a1737b.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150523_103414_resized_zpse0a1737b.jpg.html)

http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150523_103431_resized_zpsa18f9097.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150523_103431_resized_zpsa18f9097.jpg.html)
Still needs some work on the bolt safety, a replacement firing pin spring and drill and tapping the receiver for proper scope bases.

Waiting for the loan of 50 BMG reamers to finish the chambering of this short chambered barrel. Also of course the stock!

Have had lots of assistance in getting a large enough blank from several Cast Boolits members.

More to come!

[Mauser48]

Looks like a fun project! Keep us posted. Thats a great anti material gun.

[FrankG]

Serious squirrel medicine !

[woodbutcher]

:holysheep Now this sounds interesting.
Good luck.Have fun.Be safe.
Leo

[lkydvl]

Safety Lever was properly fitted now and functions as it should. Trigger ping shortened to proper length too. Still searching for a firing pin spring....and Wolfe Springs is not much help. Obviously they are just a marketer and don't have much of a clue on spring design or how to match equipment parameters to spring material. Even their "TECH" knew less than I did!

[taco650]

Subscribed!

[jmorris]

I built one a number of years ago using maddi griffin plans.

Not knowing what the receiver and bolt are made from and heat treated to would make me a bit nervous.

[lkydvl]

UPDATE!

After a plethora of issues involving the unfired, chrome lined, TAPERED bore barrel we finally got it chambered and fitted to the receiver. Cutting enough of the tops of the rifling to chamber length so the reamer pilot would fit was a real problem with the chrome lining. After that the chambering went pretty easily. Many thanks to JTKnives for the loan of his rougher and match finisher.

Extractor needs some work yet and a new firing pin spring is in need I think.

Took it home, cinched it to my heavy shooting bench and with a 25 foot strap from behind a tree did a test fire. First round took three primer strikes, 2nd took two and the third one. Using milsurp AP ammo turned out to be proof load, or near it, ammo. All showed high pressure signs with flattened primers, burnished case heads and sticking to the chamber walls. With the extractor issues they needed a tap with a rod to remove them from the chamber. No issues with the barreled action at all. Headspace was tight as ever.

Two applications of copper remover took care of the fouling out of the new barrel.

A stock blank/plank/roof beam...6' x 11" x 3 was acquired from BNelson. Nice dried walnut with some light figure in the butt. The stocking process commences!

[jrap]

Definitely looking forward to seeing the finished product!!

[jmorris]

I bought some cheap ($1.25/ea) milsurp ammo years back that was awful, sounds like you are having the same luck. Primers that either didn't work or hang fires (lots of fun with a 50 BMG) and over pressure as well.

Might try some from here.
http://www.arizonaammunition.net/custom-50-bmg

[jrap]

They have a bunch of surplus 50 available at cheaper than dirt right now. I've heard that it was pretty good

[John Taylor]

The problem with military ammo designed for a machine gun is the bullet cores are off center to get a " cone of fire" or shotgun effect. Also with older brass expect head separations. When I was working on 50 BMG single shots there were no bullets available except the Barns round nose. Military specs on machine gun ammo showed groups of 24" to 48" at 600 yards We set up an old automatic screw machine to turn out solid brass bullets that weighed 615 grains. We were able to get 3400 fps out of a 45" barrel using 230 grains of 5010 ( If I remember correctly ).

[lkydvl]

145701Where do you get such BS?

[lkydvl]

Scope bases contoured and attached after correcting an off level flat on the rear receiver ring.
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20150821_195052_zpsd2b59211.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20150821_195052_zpsd2b59211.jpg.html)
Extraction issue FINALLY corrected!

[taco650]

Keep at it. Would like to see this when its done.

[merlin101]

I bought some cheap ($1.25/ea) milsurp ammo years back that was awful, sounds like you are having the same luck. Primers that either didn't work or hang fires (lots of fun with a 50 BMG) and over pressure as well.

Many years ago I took a walk out onto the .50 cal range at Ft.Sill and saw lots of bullets laying on top of the sandy soil at the end of a long 'snail' track. Some of these tracks started about 100yds from the firing point! With low pressure like that I wonder how many squibs they had? I don't remember having any issues the few times I fired the 50.

[Skipper]

The problem with military ammo designed for a machine gun is the bullet cores are off center to get a " cone of fire" or shotgun effect. Also with older brass expect head separations. When I was working on 50 BMG single shots there were no bullets available except the Barns round nose. Military specs on machine gun ammo showed groups of 24" to 48" at 600 yards We set up an old automatic screw machine to turn out solid brass bullets that weighed 615 grains. We were able to get 3400 fps out of a 45" barrel using 230 grains of 5010 ( If I remember correctly ).

The military accuracy spec for M2 Ball is 9" mean radius at 600 yards.

[lkydvl]

Finally got a decent start on the stock...
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151002_142906_zpsfvrysrsd.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151002_142906_zpsfvrysrsd.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151002_142916_zps24ddaxgf.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151002_142916_zps24ddaxgf.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151002_144717_zps2iamspzs.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151002_144717_zps2iamspzs.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151002_150442_zpsjt43tukg.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151002_150442_zpsjt43tukg.jpg.html)
http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151002_183039_zpseivxk06b.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151002_183039_zpseivxk06b.jpg.html)

[John Taylor]

The military accuracy spec for M2 Ball is 9" mean radius at 600 yards.
The info I had was 35 years ago from military specs. and the specs may have been old at the time. We had cut several bullets in half and could see the off center core. Also found that some of the military barrel have a Stellite liner in the chamber and first few inches of the bore which does not help accuracy. And I see lkydvl thinks I'm full of BS.

[bnelson06]

Set that action together in the stock and get us an idea of how it looks

[skeettx]

on board, enjoying the postings
Thanks
Mike

[Plate plinker]

Looks like your cruising for a bruising have fun!

[lkydvl]

http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151009_182813_zpstzffzxfz.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151009_182813_zpstzffzxfz.jpg.html)

[JSnover]

Serious squirrel medicine !
They must be some serious squirrels in Oregon :shock:

I dream of falling into a project like this but in my hands it would probably never get finished.

[wonderwolf]

They must be some serious squirrels in Oregon :shock:

I dream of falling into a project like this but in my hands it would probably never get finished.


Careful what you ask for, I have half a dozen projects like this....tend to work on all at once so nothing gets finished for a few years then BAM, all at once I get 3 or 4 done heh.

[Mal Paso]

Very Cool!

I think Jack First in SD makes springs. They have a website although the catalogs are still paper. I called and talked to someone who knew all 3 thousand and some parts.

[Ballistics in Scotland]

The military accuracy spec for M2 Ball is 9" mean radius at 600 yards.

I'd have expected .50 GI ammunition accuracy to be somewhere between those rather extreme extremes. I suppose its use in sniper rifles might have caused specifications to be tightened in recent decades.

Did those rounds actually have armour piercing bullets? I can't really see why they would be used in proof loads. With those pressure indications I would want to check up on the dimensions of the barrel the unknown Mr. Mack used.

[lkydvl]

My "proof" rounds were actually just standard ball ammo. The barrel is one of the tapered bore, chrome lined variations the military experimented with. The bore started at .510 at the chamber end and tapered to .506 or so at the muzzle. We had to ream the tops of the lands in order to chamber it as I did not have a removable pilot reamer.The combination turned those standard rounds into very high pressure loads thru that barrel. Hence my usage of the term "proof load".

I have since pulled the bullets from the remaining ammo I have and will work up a loading for them when the rifle is finished.


Which I hope will be soon!

[lkydvl]

http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151016_171725_zpslg8omwbw.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151016_171725_zpslg8omwbw.jpg.html)

http://i52.photobucket.com/albums/g5/lkydvl/50%20cal/20151016_171736_zpsthbhjpui.jpg (http://s52.photobucket.com/user/lkydvl/media/50%20cal/20151016_171736_zpsthbhjpui.jpg.html)

[jhalcott]

I fired Mahdi Griffin Handgun (20" barrel) some years ago. It was an unforgettable experience. Custom handloads were what we used. A silliwet ram target at two hundred yards could NOT stop the bullet. The recoil and blast caused me to start flinching after several rounds. The first 3 were quite accurate though!

[Ballistics in Scotland]

My "proof" rounds were actually just standard ball ammo. The barrel is one of the tapered bore, chrome lined variations the military experimented with. The bore started at .510 at the chamber end and tapered to .506 or so at the muzzle. We had to ream the tops of the lands in order to chamber it as I did not have a removable pilot reamer.The combination turned those standard rounds into very high pressure loads thru that barrel. Hence my usage of the term "proof load".

I have since pulled the bullets from the remaining ammo I have and will work up a loading for them when the rifle is finished.


Which I hope will be soon!

I doubt if the bore taper, when it was only to that extent, made much of a difference to the pressure, and you might find other .50 rounds did much better. Something has to be desperately wrong with the bullet or the charge for peak pressure to be as much as a quarter of the way down the barrel, by which time the constriction could only have amounted to about a thousandth of an inch. Unless, maybe, those rounds were loaded with stretched brass, and the chamber clamped the neck onto the bullet?