50 cal w/ rifled machine gun barrel

[Southo]

Just acquired a 15b beast of an inline gun that was put together using a 27" inch section from a WWII 50 cal machine gun barrel. Probably not your average ML. Barrel length from breach is 36". Takes No. 11 caps.
The former owner only shot patched lead ball. But with the rifled barrel, I'd like to take advantage of that twist (rate unknown) for several hundred yards down range.
Brand new to Muzzleloading so don't hold back. I want to not only understand the basics, but would, of course, want to load for the potential of the rifle. Please feel free to suggest type of powder, mold, lead makeup, powder coat, lube or whatever comes to mind and links.
Although this would look awesome over the mantle, I feel there is real potential here.
I would post a pic or two here but I'm not too tech savvy, but can send via email at least.
Thank you all ahead of time. This sight is so full of knowledge it's overwhelming for the first timer. Like anything though, the more times you visit, the maze begins to reveal itself.

[mooman76]

You can figure out the twist with a bit of math. Insert a cleaning rod with a good tight cleaning jag and patch. Mark the rod and count the turns. I don't have any idea of the twist but am sure it will be tight. A paper patched bullet would probably be one of your best bets with your setup.

[Ballistics in Scotland]

I had the chance to bring back a 14..5mm. Soviet KPV barrel with chamber amputated (as freely importable to the UK as a walking-stick) from a certain Middle Eastern country. But I decided that the fast rifling twist tipped the balance against using up my baggage allowance. I think you could use the .50BMG barrel for a muzzle-loader, but it would be best suited to a very heavy benchrest gun for elongated patched bullets, as enjoyed a limited following in the 1850s or so, and an even more limited one today. The originals would have an even heavier barrel (casting yours into a tube with lead?), and a false muzzle for loading. I would prefer more than a 27in. barrel, though, and it might benefit from the use of metallic cartridge primers. If it uses a regular rifle or musket nipple, you should be able to get one to screw in.

[johnson1942]

please see you pm/s

[koger]

I bought one similar, not an inline, but sidehammer, made from a M2 barrel, still had bronze bushing on the end, with a peep sight and fine bead. The stock was broken, I fixed it and glass bedded the barrel, with .015 patch and .490 swaged lead ball, it shot a ragged hole at 50-60 yds and did same with open sights,. I put fixed sights on it, shot it as a chunk rifle, placed 10th overall and under time or two at Alvin York 60yd match, and have a whole handful of Gold, Silver and bronze NMLRA medals I won at friendship with it! It had a good homade lock, Jager set triggers out of a Mauser, and after I lapped the barrel, would shoot so good it was scary. I gave a whole$75 for it! Mine shot best with 110grs 2ffg!

[Nobade]

It should have a 1:15 twist. It'll be all about 700 - 900 grain paper patched bullets and large charges or powder.

-Nobade

[koger]

Mine was WW2 era, it had a 1-48 twist best I could tell.

[Outpost75]

Mine was WW2 era, it had a 1-48 twist best I could tell.

If it was a 48" twist, it sure was not a cal. .50 BMG barrel, they were all 1:15", and the M48 Spotting Rifle for the 106mm recoilless rifle was 1:12"

[Southo]

Could you suggest bool it type/shape, metal makeup, and a mold source.
does/can powder coating replace paper patching

[johnson1942]

i have a 700 grain bullet mold hollow based that could fit the bill. find out the twist first on that barrel. put a tight lubed patch on a ramrod. push slowly to the bottom of the barrel. make sure it engages the grooves well and slowly pull back untill it makes one complete turn only. then measure how far it backed out and that is the twist of the barrel. if it is 1/15 twist you will need at least a 700 grain bullet. that mold of mine would work great in paperpatching, would give you a good deal on it. my pm/s are working now.

[Southo]

Johnson1942 has been extremely helpful in sorting this rifle out. I determined the rate of twist, as suggested, by inserting the well-oiled jag down the barrel, attached a piece of masking tape at the muzzle and slowly pulled it out measuring the distance traveled after one revolution. This I repeated several times (very intertaining) measuring ~16". That extra inch probably came from starting the jag until it bit the grooves. Regardless, two of you here and on the internet said 1 in 15. So it is.
Barrel is 36" from muzzle back to front of breach. Barrel OD at muzzle is 1". Barrel ID is?? This is where I'm having trouble getting an exact measurement. I have digital calipers that give readings from .488 all the way to .502. I think it is my inability to line up the top of the lands to measure exactly across the center from land to land. Catching a groove or two would probably cause that spread. Because Looking very closely (because of the twist), the lands don't line up across the center.
Since a heavy grain bullet will be paper patched, it is suggested that it be run through a reducing die -.008. So ordering the right reducing die the 'first' is the true beginning.
If any of you have this type of barrel or a past notation in a log, please let me know what you came up with to compare to my eradict measurements.
Thank you ahead of time

[Nobade]

The bore should be .500". If you have access to any pin gauges, that is the way to check it easily.

-Nobade

[Southo]

Thanks Nobade,
I'll just contact a machine shop that is willing to check the bore for a fee.

[Ballistics in Scotland]

Johnson1942 has been extremely helpful in sorting this rifle out. I determined the rate of twist, as suggested, by inserting the well-oiled jag down the barrel, attached a piece of masking tape at the muzzle and slowly pulled it out measuring the distance traveled after one revolution. This I repeated several times (very intertaining) measuring ~16". That extra inch probably came from starting the jag until it bit the grooves. Regardless, two of you here and on the internet said 1 in 15. So it is.
Barrel is 36" from muzzle back to front of breach. Barrel OD at muzzle is 1". Barrel ID is?? This is where I'm having trouble getting an exact measurement. I have digital calipers that give readings from .488 all the way to .502. I think it is my inability to line up the top of the lands to measure exactly across the center from land to land. Catching a groove or two would probably cause that spread. Because Looking very closely (because of the twist), the lands don't line up across the center.
Since a heavy grain bullet will be paper patched, it is suggested that it be run through a reducing die -.008. So ordering the right reducing die the 'first' is the true beginning.
If any of you have this type of barrel or a past notation in a log, please let me know what you came up with to compare to my eradict measurements.
Thank you ahead of time

It wouldn't, I suppose, have an odd number of grooves? That would present some difficulty in measuring the true land and groove diameters. I don't know of any cases of a .50 Browning barrel having this, but odd examples of anything is possible. There is no benefit in an odd number of grooves for any process in common use for rifling military barrels nowadays, but when grooves were cut one at a time, in a large number of shallow scrapings, a land at 180 degrees to the groove provides more rigid backup for the tool.

Pin gauges are a counsel of perfection in such a situation, but expensive if you buy the set. You can buy a single 12.7mm. carbide gauge cheaply from China on eBay, but a piece of drill rod or brass rod are about as good for this purpose, and you will surely find other uses for them.

Koger's 48in. twist would indeed be unusual for almost any modern firearm, and entirely incapable of stabilizing the .50BMG bullet. My guess is that it was from some other kind of spotting rifle.

[Sharpsman]

And useless as a side saddle on a pizz ant!!

[Ballistics in Scotland]

And useless as a side saddle on a pizz ant!!

Not at all. I found Koger's account of his rifle's performance puzzling in the extreme, if it had really been made from a .50 BMG barrel. But if it really has a 48in. twist whatever it came from, it would be far better for a ball or light-bullet muzzle-loader.

[Southo]

My thought about going to a machine shop is they would have a "set" of pin guage in case the bore was anything but .5" or 12.7mm.

[johnson1942]

i did a lot of research this morning on the internet and it has 8 lands and grooves. gave every thing info about it but the top of the lands bore diam. i suspect it is .50. probably a very easy way to check it is get a cheap drill bit that is about 1 or 2 thousands under .50, around a .499 or .498 and if it inserts in the end with out taping it in, it is .50. in that case a .492 resizeing die would just right for sizeing a bullet for paperpatching. the specs on the internet said. 36 inches long. 1/15 twist with 8 lands and grooves. Southo will get this gun shooting paperpatch and i bet it turns out to be a long distance paperpatch good shooter. if you can find a bolt that measure .5 diam, see if that slides in the bore also.

[Southo]

Had the bore checked by a local machine shop using a pin gauge. Measures .501

[Nobade]

In case you're still looking for a mould, this might be a good one...
http://www.bpcr.net/forum/viewtopic.php?f=8&t=7164

A little large but can be easily sized down.

-Nobade

[Southo]

Thanks for the lead. But just acquired a 724 gr round nosed smooth sided conical bottomed mold from Roger Johnson.
just waiting on info for a pass through .494 die for paper patching

[Nobade]

Great! Sounds like you are well on your way to making that very interesting rifle speak again.

-Nobade