Swamping a pistol barrel

[andy49]

I would like to try swamping  a 7/8” by 10” octagon 45 cal. pistol barrel.  Can someone give me any guidelines that I should follow?
Is a 7/8” barrel  adequate to start with, for sidewall thickness? I am finding only 1” barrels offered from barrel makers for a swamped pistol barrel and wondering if this is a minimum for safety. Also if 7/8 is O.K. what type of profile should I use from breach to muzzle.
Thanks
Andy

[bob in the woods]

Since this is a pistol, the charges used will probably be less than a rifle; and my .45 cal rifle has a 13/16ths barrel.
I think 7/8th is enough re strength, but it is about the architecture so swamping from 7/8 to 13/16th isn't going to stand out as much as from 1 in etc. If you started at 7/8th then went to 12/16th then flared back out to 13/16ths at the muzzle  it might look OK, but if you're going to go to the trouble, ….why settle for something that's not exactly "right" ?

[JCKelly]

The steel bar from which your barrel was made was most likely cold drawn to finish round bar. This means it is full of residual stresses.

Huh?

This means you must carefully remove the same amount of metal from each side.
Otherwise it will bend.
Just like that, bend.
Surprising, at least it surprised me when I saw it happen & I shoulda knowed better.

Assuming you do this with a file, I'd suggest taking a bit off one flat, then off of the opposite flat.

Do this to all the flats, one at a time, don't be in a hurry to remove too much metal from any one flat at any one time.

[Acer Saccharum]

You can file tell-tale grooves with a triangular file on each flat where you want the waist to be. I think you could do this pretty accurately by eye. Stop filing when the groove disappears.

I just made that up, and don't know if it's a good or bad idea. 

[jerrywh]

 Will it be octagon all the way or octagon to round?  I proofed a pistol barrel with a .165 wall at the breech. It was a rapid taper to where the muzzle was only .032 thick. The barrel was 10" long. Swamped round all the way. The steel was 1137.  I actually tried to blow it up but quit at 150 grs or fffg Goex. Twice.  It never phased it. A standard load for a pistol like that is only about 2 grs. The barrel was annealed in a furnace so it never had any stress.  I would expect the same results with 12L14. as the specs are about the same.

[Bob Roller]

You can file tell-tale grooves with a triangular file on each flat where you want the waist to be. I think you could do this pretty accurately by eye. Stop filing when the groove disappears.

I just made that up, and don't know if it's a good or bad idea. 

The idea of a witness mark is a good one.The outcome depends on your skill with a file.
I would start (carefully)with a half round Vixen file. You might be able to get one at an
auto supply store such as NAPA.They seem to have a more dedicated operation and fewer fuzzy dice that some of the others.

Bob Roller

[B.Habermehl]

Starting with a 7/8 in barrel take it down in a straight taper to 13/16 at the muzzle. The waist can be as small as 3/4 in. You need to work opposite flats first, call these top and bottom. Then the next set of opposite flats to work are the sides. Then the obliques. Keep checking for squareness between flats, and watch that you don't develop a twist over all. Till your done your fore arms will look like Popeye's, at least they will feel that way. BJH
BTW You need a set of dial calipers to keep track of what your doing. I hand filed one pistol barrel this way, it turned out just fine, but never again, too dang much work.

[LRB]

  I did an 6" barrel by taking off about an equal amount on all flats using my knife grinder to rough in, then filing. I did as Mr Kelly said working opposing flats and checking the waist area with dial calipers.  From there just kinda eyeballed it to be reasonably even in the flats. Came out fine. I did not true in thousandths, but just in fractional measurements. Okay for pistol barrels, but I would not care to do a rifle that way.

[smart dog]

Hi,
I've swamped several pistol barrels and a short rifle barrel.  The rifle was a Green Mountain barrel.  Talk about long sessions at the grinder.  Anyway, what the other posters say about index marks is the way to go.  I file narrow index bands, which are easier to measure for depth and barrel diameter.  It takes some work to grind down the barrel to the marks but then it takes an equal amount of work to smooth the inevitable ripples in the barrel.  However, with a pistol barrel, that is not too bad at all.

dave

[andy49]

Thanks for all the suggestions. I planned on profiling from 7/8 at the breech to 3/4, 5" from the breech back to 7/8 at the muzzle, octagon all the way. I have read that this will produce a clearer front sight as well as looking good.
This profile would give me .15" side wall at the waist.
Andy

[smallpatch]

Wow, you all have WAY more energy than me.  I'd just buy a swamped barrel to begin with!!!

[Mike Brooks]

I'd have at it with my angle grinder,finishing up with a file. I might even measure a couple times while I was grinding.

[jerrywh]

 I did a octagon to round fowler barrel about 36" long back in 1975 by hand with files. That cured me of that notion.  I now do mine in a mill with a index head and a adjustable tail stock.  By hand you can get a nice barrel you will also get arthritis in your hands for the rest of your life and maybe your back also. Well-- everybody has to do it once I guess. you can learn a lot doing that sort of thing . The most important thing you may learn is not to do it again.  The gun makers in the 18th and 19th century ground them down on a large grind stone with an adjustable fixture to hold the barrel in. If I wanted another project it would be to build one of those grinding tables like this.

PS. You can swamp a barrel with this rig by making a curved  carriage.

[blienemann]

I hand filed a swamp into a 1 1/8" straight 42" x .54 GRRW barrel when I was younger.  Have seen a lot of originals, and the flats are not even in width nor smooth in profile, so did it by eyeball like Mike B above.  I'm not a machinist and have no tools, so approached it as a farm boy.  Filed a few notches to depth I wanted with chain saw file.  Used an old 49 cabinet rasp to rough out going across the flats - much easier on the body, then coarse and fine rasps lengthwise to clean up only the flats that show - like the old ones.  Took parts of two days, but was still in good football shape.  It shoots real fine.  The metal stresses comment is interesting, but fortunately I didn't know about such things.

Also picked up a poorly built pistol with a straight, high quality barrel, and hand filed the flats on the top or visible flats only - as bottom flats already inlet.  Then put slight "swamp" in the wood to finish the appearance.  Looks and feels like a swamped barrel, and shoots very well.

Have filed tapers and/or swamps in quite a few pistol barrels.  Would order a 42" rifle barrel with fast pistol twist, then cut, shape and breech sections for projects.  Short barreled pistols are usually for show, and have shot fine from my experience.

Back in the days before swamped barrels, we did lots of shimming, tapering bolster, and "swamping the forestock" to get the architecture closer.  Today's variety of barrels sure is nice, though some "standard patterns" are not real close to the profile of old barrels.  Bob

[jerrywh]

 Who sold muzzle loading barrels in 1961??  I never could find anyone back then.  Bill large had an add in the American rifleman but I don't think his name was on the add. Only a phone number or address.

[Bob Roller]

Who sold muzzle loading barrels in 1961??  I never could find anyone back then.  Bill large had an add in the American rifleman but I don't think his name was on the add. Only a phone number or address.

Bill Large was running a constant ad in Muzzle Blasts which caters to the muzzle loading fraternity.The regular 22 / 30-06 /45ACP NRA members of that time had little or no interest in Bill Large or his barrels.

Bob Roller

[jerrywh]

 Out here in Oregon I never heard of muzzle blast in 1961. but somewhere I saw a Dixie gun works add and I got one of their catalogs.  I still have it somewhere.

[Old Ford2]

Hi
I am in the process of tapering an octagonal .69 cal. pistol barrel.
It is 12" long  1 5/16" at the breech and 1" at the muzzle.
It was quite easy with the milling machine.
Putting a taper like this, really shifts the balance point.
This will be mated to a .69 cal. plains rifle, so that the proud owner can hunt T-Rex with confidence.
I have swamped barrels previously, without any issues.
Everyone should have a milling machine!
Fred

[andy49]

Thanks for all the responses. I have found with building pistols that the store bought parts for a HC build are not readily available. I now make everything, but the barrel and lock and now I am finding that the barrel I want is not available and that’s why I am interested in swamping my own barrels. The lock sizes are also not available ( so I use less than perfect locks) and I hate the thought of having to build these next. 
Andy

[jerrywh]

Andy49 
  You actually might really enjoy making a lock. After you make a few you will really know what makes them work bad or well.   

[Bob Roller]

Thanks for all the responses. I have found with building pistols that the store bought parts for a HC build are not readily available. I now make everything, but the barrel and lock and now I am finding that the barrel I want is not available and that’s why I am interested in swamping my own barrels. The lock sizes are also not available ( so I use less than perfect locks) and I hate the thought of having to build these next. 
Andy

The locks are a PITA and I speak from experience. A lathe and vertical mill are mandatory if you are going to do this specialized work.

Bob Roller