Questions regarding swivel breech barrels for pistols.

[Rolf]

Remember Runar? He  made the Norwegian mailman protector, http://americanlongrifles.org/forum/index.php?topic=11499.msg109442#msg109442

He has bought Dave Waters book "Building a swivel Breech" and would like to build a swivel breech pistol with 10" long swamped octagonal barrels. caliber 0.50 . He does not write english, so I'm posting for him.

1a.If we want to install touch hole liners, how thin can the barrel wall at the breech safely be?
2a. Could anyone recommend a safe profile for a light weight swamped 0.50 caliber barrel?

1b. If we skip touch hole liners and use a coning tool instead, how thin can the barrel wall at the breech safely be?
2b. Could anyone recommend a safe profile for this version of barrel?

Best regards
Rolfkt

[Dphariss]

This will make the wall thickness less critical.
But there much be enough thickness so it can be threaded safely for the breech plug,
The hemispherical cup should be slightly under bore size so that a ball cannot block the vent if loaded without powder.
I cut them in the mill with a ball end mill or in the lathe.



Hope this helps.

Dan

[Jim Kibler]

After using one of Tom Snyder's internal coning tools, I wouldn't consider using a touch hole liner on a new build.  I would think a 13/16" breech end to be the minimum distance across the flats for your 50 caliber.  If planning on a swamped or tapered profile, you could probably get away with a minimum wall thickness at the small of the barrel somewhere around .080"-.090".  I wouldn't plan on too much of a flare at the muzzle as this will be counterproductive with a swivel breech.

[Dphariss]

After using one of Tom Snyder's internal coning tools, I wouldn't consider using a touch hole liner on a new build.  I would think a 13/16" breech end to be the minimum distance across the flats for your 50 caliber.  If planning on a swamped or tapered profile, you could probably get away with a minimum wall thickness at the small of the barrel somewhere around .080"-.090".  I wouldn't plan on too much of a flare at the muzzle as this will be counterproductive with a swivel breech.

But a 50 caliber requires a 5/8 or similar breech plug. 13/16 will leave less than 3/32 wall at the threads. . In effect the bore at the breech face is more like .625-.628. So there is a high stress point at the face of the breech or just behind it as the pressure tries to blow the breech out. A 50 caliber if loaded to 8000 psi, will produce about 1600 pounds of breech thrust if the grooves are .010 deep. Hanging 1600 pounds on a wall this thin would not be my first choice.
Thus, not being an engineer, a 7/8 will give a wall thickness I would be more comfortable with. Just under .125".
Eventually a soft barrel will erode with use, faster with a thin web between the pan and the internal cone and the vent will need bushing anyway.

Dan

[Jim Kibler]

Well, I am or perhaps was an eingineer, but one thing I have learned from that expereince is that trying to predict or model an occurance is often very complicated and difficult.   Although sometimes a bit more risky, there is nothing better than experience to guide us.  There have been a number of 13/16" 50 caliber rifles made of 12L14 that have survived without incident.  With a pistol charge, and perhaps a little better material, the likelihood of a problem would be even more remote.  A 7/8" breech would add to the safety factor. 

[bob in the woods]

I'm interested in what kind of pressures we are talking about in a typical pistol load?  Is 8000# about right?
I shoot a .50 with a .490 ball and 40 gr 3F , which seems about average in this neck of the woods .

[D. Taylor Sapergia]

I have a copy of "The English Pistol" by Beebe and Bingham.  I remembered that many of the pistol barrels described in the book were very thin walled, so I flipped it open and the first one I checked out was on page 16 - a pistol with a full octagonal tapered barrel 15/16" at the breech and 13/16" at the muzzle.  It is a .69 calibre, so here's the math...at the breech there is a wall thickness of .12375" - that's less than 1/8"!!  You wouldn't need a liner in that breech!!  The muzzle has a barrel wall of .06125", so if you added .020" for the rifling, it would be just over 1/16" thick wall at the muzzle.
I have found this theme running throughout the book - it is normal. that said, I personally would build it heavier.  For the swivel project, I'd use barrels that were 7/8" at the breech and swamped but not flared to about .700" at the muzzle.  That'll give you the meat you need to breech it safely, and the light weight you want at the muzzle.

[Dphariss]

I have a copy of "The English Pistol" by Beebe and Bingham.  I remembered that many of the pistol barrels described in the book were very thin walled, so I flipped it open and the first one I checked out was on page 16 - a pistol with a full octagonal tapered barrel 15/16" at the breech and 13/16" at the muzzle.  It is a .69 calibre, so here's the math...at the breech there is a wall thickness of .12375" - that's less than 1/8"!!  You wouldn't need a liner in that breech!!  The muzzle has a barrel wall of .06125", so if you added .020" for the rifling, it would be just over 1/16" thick wall at the muzzle.
I have found this theme running throughout the book - it is normal. that said, I personally would build it heavier.  For the swivel project, I'd use barrels that were 7/8" at the breech and swamped but not flared to about .700" at the muzzle.  That'll give you the meat you need to breech it safely, and the light weight you want at the muzzle.

Given the depth threads in taps large enough to tap a 69 hole I wonder what the wonder how thick the metal is at the threads?
But we see many thin barreled guns ML and otherwise. Look to the cylinder walls of some 1st gen Colt SAs in 45, and this had a locking lug cut as well. Many of the recent/current production guns have a dimple at this cut location when the chamber is examined.  Probably from the proof load.

I tend to over engineer things so I like some what heavier breeches.

Dan

[D. Taylor Sapergia]

So do I Dan.  I'd never build a pistol with a barrel such as the one I described.  I'd be in great fear of it blowing.

[bob in the woods]

I prefer the 7/8 breach on a .50 cal, but I remember that there are a few 13/16th .50 cal barreled rifles and 7/8 ths .54 cal barreled rifles that I've seen over the last while. I believe that the barrels were supplied by Getz, so it would be interesting to hear from Don as to their breaching .

[David Rase]

My first gun from a plank was built using a Don Getz 42" 13/16" .50 caliber barrel.  Had a small siler lock and an Ampco touch hole liner.  Never experienced any problems.  Even with the long thin barrel it was very accurate.  Wish I had it back to show people what first guns can look like.  It sure was ugly.  Thank God I met Bob Lienemann and he got me educated on what colonial longrifles should look like. 
DMR

[D. Taylor Sapergia]

Many years ago, I built a longrifle around the client's 42" x 13/16" x .45 cal barrel.  It was percussion and had a drum and nipple.  The drum blew out much to my embarrassment, and I got it back to repair.  I don't remember what I did, but it seems to me I converted it to flint with a patent type breech....free.  The rifle was shortly thereafter stolen from the client's Vancouver home, never to be seen again.  I've never built another muzzleloader with that light a barrel...7/8" is as small as I'll go, even in .32 cal.

[bob in the woods]

One of the most accurate rifles I had was a 3/4 in barrel .36cal tennessee style flintlock. Small Siler lock, and if I remember correctly , the barrel came from Riley Smith in Florida. Long, slim,light, but balanced well, and shot like a laser!!   I really liked it for off hand matches, even at 100 yds.  It liked 60 gr 3F, and a .350 ball with a .20 patch .  I considered ordering one of those light weight 13/16 .50 barrels for a hunting rifle,but I'm just too taken with the B weight swamped ones. They make up into about the best deer hunting rifles going IMO.

[Dphariss]

Many years ago, I built a longrifle around the client's 42" x 13/16" x .45 cal barrel.  It was percussion and had a drum and nipple.  The drum blew out much to my embarrassment, and I got it back to repair.  I don't remember what I did, but it seems to me I converted it to flint with a patent type breech....free.  The rifle was shortly thereafter stolen from the client's Vancouver home, never to be seen again.  I've never built another muzzleloader with that light a barrel...7/8" is as small as I'll go, even in .32 cal.

I built a rifle for Daniel when he was 12 its a 7/8 x 36 x 45. He never had any problem shooting it well offhand and he was always a skinny kid. Its a little short for him now but still shootable.



Dan

[Rolf]

Thank you for your input. It seems the majority advises against making a 0.50 caliber barrel with a 13/16 breech. We don't want to use a larger breech, partly because we want a slim profile on the pistol and partly because all the measurements in the Waters book is for 13/16 breech barrels. I guess the sensible thing to do is to chose a small caliber.

Both Rayl (Stonewall creek stocks them) and Green mountain make strait octagon barrels, caliber 0.45 with 13/16 breeches. So I gather a 0.45 caliber swamped/tape rd barrel with a 13/15 breech should be safe. Any comments/opinions?

Best regards

Rolf

[D. Taylor Sapergia]

You won't likely run into problems if the workmanship is superlative, especially in a pistol with it's inherent low pressures.