Twist rate for .50 Caliber Pistol

[Eddie2002]

I've started pretty much a scratch build for a .50 caliber cap lock pistol. The barrel is being made out of a 1 inch piece of stainless steel round stock which I'm hogging out with a 1/2 inch drill and following up with a clean up using different grits of paper. Bore length will be around 10 1/2 inches which is the length of the drill I'm using. I'm not drilling through and installing a breach plug, just dead ending the bore and leaving plenty of metal at the breach.

Just for hoots and hollers I'm making a rifling jig out of some of the stuff laying around the shop and plan to use it on the barrel. I'm getting ready to coil and weld the 3/16 round stock around the control cylinder and am wondering what twist rate I should use. Most of the pistols I own are either smooth bore or a 20 inch twist.

I'll be shooting PRB with this gun and since it's my first attempt I would like to try to get it right. Don't even know if the build will work, I need to convert one of those 60's crappy Japanese flintlock actions I've had sitting on the shelf for years over to caplock unless I can track down a decent one at good price.

[Tatume]

If the bore is blind, how are you going to start the rifling bit?

[Eddie2002]

From your question it sounds like I'm trying something you are unfamiliar with or isn't the standard way to to cut rifling. I'm coming in from the muzzle with the cutter and backing it out to reset the depth for each pass. Planning on multiple passes per rifling since I can't take a single deep cut. There will be a short section of the bore at the chamber that won't get rifled but can't see any reason to rifle the chamber anyways. It's not like I have access to a complete machine shop and thousands of dollars worth of equipment to throw at this project, it's all pretty much back yard machining.

My thoughts are why use a breach plug if you can make a barrel without one, there are plenty of welded breach plugs and blind bores in use. I've made a couple barrels with breach plugs and they are just another hassle for machining and once in place they never need to come out so I decided to skip making a breach plug with this barrel and plan for a blind bore.

Just would like to know what twist to shoot for, heck I don't even know if the rifling jig will work but I'll never know unless I try. Thanks for your question and I didn't mean to be snappy with my reply.

[megasupermagnum]

The stainless still is likely what will get you. Assuming you are using a proper alloy for a gun barrel, it cuts very hard compared to regular steel. As for twist rate, My TC scout pistol in 54 caliber has a 1:20" twist, and it will hold its own against the TC 1:48 twist rifles. It is incredibly accurate.

[Eddie2002]

Thanks, I'll go for the 1 in 20 twist. The stainless is mildly magnetic and was salvaged from some medical equipment that was getting tossed out. It's a full 1 inch thick and machines well on my Southbend heavy 10 as long as I take it slow. With a 1/4 inch sidewall there is no reason the bore can't stand up to the pressures a BP pistol generates. Most rifles barrels are made out of a mild steel, have thinner walls and can stand charges three times a pistol load. I'll proof test the barrel once it is finished just to be safe. Thanks again

[Outpost75]

Many years ago I made a .50 cal muzzleloader using a chunk of .50 BMG barrel which worked fine. Do not recall what the twist was, but shouldn't be hard to determine...

[mooman76]

A guy on another board just made one from a 20mm barrel off a F-16

[oldracer]

I made my single shot cap lock pistol with a Green Mountain pistol barrel which has a 1 in 18 twist. I bought the barrel, lock, trigger and sights from Track of the Wolf. I would suggest doing this way first so you get the hang of making a pistol since it is different than putting together a rifle. I was going to make mine 50 caliber but my mentor talked me out of the larger size since it will be very, very nose heavy.

[Tatume]

From your question it sounds like I'm trying something you are unfamiliar with or isn't the standard way to to cut rifling. I'm coming in from the muzzle with the cutter and backing it out to reset the depth for each pass. Planning on multiple passes per rifling since I can't take a single deep cut.

Yes, I am unfamiliar with your process. How are you going to adjust the depth of cut from the muzzle end, while the bit is all the way at the bottom of the blind hole?

Thanks, Tom

[Nobade]

No way in He** are you going to be able to get a decent bore finish or straightness with a drill bit followed by sand paper. A gun drill followed by a pull type reamer is the normal way to do that and you need a through hole to make it happen. Likewise, rifling cutters only work in one direction so you'll have to come up with another way to do that. Starting with a piece of honed tubing would be the way to go if you want to do this.

[mooman76]

1-20 sounds about right for a BP pistol. They have tighter twists than a rifle.

[Eddie2002]

Thanks everybody for the input. From the general replies looks like I'm wasting my time. I'll scrap the idea and recycle the stainless steel bar stock.

[arcticap]

Thanks everybody for the input. From the general replies looks like I'm wasting my time. I'll scrap the idea and recycle the stainless steel bar stock.

Why not try to make a smooth bore?
It doesn't need to be perfect.

[Eddie2002]

"Why not try to make a smooth bore?
It doesn't need to be perfect."
Yeah I'm probably going that route and put the rifling jig on the back burner. The rifling jig is finished enough for a simple operation check out and pushing the cutter down the bore gives a bad chatter so that's pretty much a bust.

Have the bore pretty much drilled and don't want to waste all the time I've already put into it so a smooth bore is a given. Forgot how tough stainless steel is to machine. LOL