Author Topic: Barrel Harmonics (Read 11531 times)

eagle24 · « **on:** August 18, 2009, 11:43:37 PM »

Just a thought and a question. I have a Rice straight 7/8" X 40-1/2" barrel (.45 cal) that I am going to use for my next rifle. I was considering filing a mild swamp and had thought about laying it out and filing index cuts at various points to keep me on track. Would I be messing up the harmonics of the barrel and making it less accurate to do so?

northmn · « **Reply #1 on:** August 19, 2009, 12:06:55 AM »

I sincerely doubt it. A good ML barrel is relatively soft steel and does not vibrate like a modern barrel.

DP

Z. Buck · « **Reply #2 on:** August 19, 2009, 12:37:08 AM »

putting a barrel in a a wood stock will mess up the harmonics more than adding a swamp...but i dont think that is a big of an issue with muzzle loaders as with modern bolt guns that they shoot 1000 plus yards with

Birddog6 · « **Reply #3 on:** August 19, 2009, 01:31:32 AM »

I don't think you are going to mess up anything, except maybe some files... It will take forever to file enough metal off that barrel to make any noticeable difference. And then you run into keeping all the flats even & the swamp smooth & gradual & etc. You may be biting off way more than ya bargained for & once ya start you are in & no backing up...

The last guy I saw swamping one worked on it 2 months & never did finish it... Now it is a real good tomato stake.
I suggest ya use it like it is or buy a swamped barrel & save yourself 6 weeks of filing.......

Tim Crosby · « **Reply #4 on:** August 19, 2009, 01:52:48 AM »

Quote from: Birddog6 on August 19, 2009, 01:31:32 AM

I don't think you are going to mess up anything, except maybe some files... It will take forever to file enough metal off that barrel to make any noticeable difference. And then you run into keeping all the flats even & the swamp smooth & gradual & etc. You may be biting off way more than ya bargained for & once ya start you are in & no backing up... The last guy I saw swamping one worked on it 2 months & never did finish it... Now it is a real good tomato stake.
I suggest ya use it like it is or buy a swamped barrel & save yourself 6 weeks of filing.......

Really, about 35 years ago I thought it would be a good idea......Ha, the rifle looked good the barell looked like....it was filed by a group of unhappy gnomes. Now, I have seen them done and they look ok but they are few and far between. Good luck.

Tim C.

Roger Fisher · « **Reply #5 on:** August 19, 2009, 01:56:00 AM »

An excercise in futility

J. Talbert · « **Reply #6 on:** August 19, 2009, 02:17:51 AM »

I hand swamped a pistol barrel some time ago with the method you describe.

For a rifle barrel, I suggest you set it on the workbench, carefully measure it and determine the final dimensions you desire, and then pick up the phone a order a swamped barrel.

Jeff

Dphariss · « **Reply #7 on:** August 19, 2009, 04:57:16 AM »

Quote from: GHall on August 18, 2009, 11:43:37 PM

Just a thought and a question. I have a Rice straight 7/8" X 40-1/2" barrel (.45 cal) that I am going to use for my next rifle. I was considering filing a mild swamp and had thought about laying it out and filing index cuts at various points to keep me on track. Would I be messing up the harmonics of the barrel and making it less accurate to do so?

Save yourself a lot of work and buy a swamped barrel.

Dan

Dale Halterman · « **Reply #8 on:** August 19, 2009, 02:22:48 PM »

Chuck Dixon told me he hand filed a swamp into a barrel once, so it can be done. But that was in the days when they weren't so easy to buy.

I notice you said "mild swamp". Is the issue that most modern made swamped barrels are more radical than the originals you have seen? If so, you might want to talk to John Getz. They have a pattern, I think they call it the "standard light" or something like that, that may be what you are looking for.

If you do order from John, keep in mind that he runs a small shop and the barrels are hand made, so it can take a while to get it. Probably still quicker than hand filing, though.

Dale H

Long John · « **Reply #9 on:** August 19, 2009, 03:14:48 PM »

G,

I've swamped barrels and it is NOT the horror story others seem to think it is.

Mark stations aling the length of your barrel every 4 to 6 inches. Calculate how much swamp you want and where the waist will be. When you do this make sure that you will have enough steel at the waist! These calcs will then lead you to so many thousanths of an inch decrease in dimension from bore center line to barrel flat at each station. That is so many thousandths of an inch decrease in bore-to barrel-flat distance. It is also the depth of your guide grooves at that station. Now, carefully file a transvers sqare-bottom guide groove across each flat at each station to the precise depth you need to achieve the decrease in dimension you want at that station. All grooves at each station should be the exact same depth (+/- .001).

Now, buy your self a nice new 12" Nicholson single cut mill bastard file and some sidewalk coloring chalk. Put a little chalk on your file, put the barrel in the vise and draw file each barrel flat until you get down to the bottom of the transverse grooves at each station. The net result will be a nicely swamped barrel! The whole job costs me about 2 hours per foot of barrel, but we are not racing, we are building rifles. The most critical part is filing the transverse grooves! Too deep and you have a tomato stake!

Best Regards,

JMC

Don Getz · « **Reply #10 on:** August 19, 2009, 04:04:47 PM »

Oh yeah John, I just noticed you live in New Jersey, kind of explains your thinking (Joke). Why are there so many depressed people in New York?..........They found that the light at the end of the tunnel was New Jersey. Sorry John, I
didn't get to pick on you much at Dixon's.............Don

eagle24 · « **Reply #11 on:** August 19, 2009, 04:08:32 PM »

Quote from: Dale H on August 19, 2009, 02:22:48 PM

I notice you said "mild swamp". Is the issue that most modern made swamped barrels are more radical than the originals you have seen? If so, you might want to talk to John Getz. They have a pattern, I think they call it the "standard light" or something like that, that may be what you are looking for.

Yes. I saw a couple of rifles at the CLA Show that a guy had swamped and they looked really good. Just a mild taper like a lot of originals I have seen. You almost had to look down them to tell they were swamped. I'm gosh awfull slow at everything. I don't need to add 6 weeks of filings to a build, so I may punt the idea.

J. Talbert · « **Reply #12 on:** August 19, 2009, 06:52:20 PM »

G,

Just in case you do decide to do it, here's the method I used on the pistol barrel. After determining the position of the waist and the depth of the swamp, I experimented until I found how many hacksaw strokes got me to the proper depth with a nice new hacksaw blade. In my case it was five.
Starting at the waist I cut five strokes on the first flat and then did that all the way around on each flat. Next, I moved an inch in each direction and did it again with only 4 strokes.
Another inch in each direction and only 3 strokes, etc.
Of course I did this quite carefully to be sure not to go too deep, but once this was done, I filed down to bottom of the marks, dressed up the flats and that's pretty much it.

Jeff

Ed Wenger · « **Reply #13 on:** August 19, 2009, 06:58:55 PM »

I can't speak to the effort or ability involved in swamping a barrel, but Zack hit the nail on the head in regards to accuracy... The pressures associated with black powder are no where close to what you get with a modern, center fire rifle using smokeless powder. Hence, harmonics are greatly reduced and aren't nearly the factor associated with modern rifles. That's why any precision rifle will be glass (or aluminium) bedded, and have a free floating barrel. Plus, the stock will be made of a composite material that's not affected by environmental conditions (moisture). I wouldn't worry about the accuracy. Best of luck if you decide to swamp it yourself.

Ed

Dennis Glazener · « **Reply #14 on:** August 20, 2009, 12:08:43 AM »

Speaking of barrel harmonics, years ago I had a conversation with Clyde Hart, maker of precision benchrest rifle barrels, and he told me this:

He had a family of benchrest shooters, holders of several world records, that would send him back barrels that had "dead straight" bores! They had a theory that a barrel with a "dead straight" bore would not be consistent in its vibrations (harmonic's). (in benchrest consistency is what you want) He said he did not know if he agreed but who could argue with their success!
Dennis

Pete G. · « **Reply #15 on:** August 20, 2009, 01:26:57 AM »

Don't forget that you really only need to file 5 flats, not eight. The three inside the stock are hidden, so no need to spend any time on them. Many old rifles were built without flats on the bottom side of the barrel and the stock was not fit closely to the bottom of the barrel either.

Long John · « **Reply #16 on:** August 20, 2009, 04:45:25 PM »

Pete,

With all due respect, I must disagree. As you shoot a rifle the barrel will heat up. If the barrel is not symetrical I would expect the heating will cause the barrel to bend toward the thinnest side.

Personally, I have to agree with what I believe it was Horace Keppart said: "Only accurate rifles are interesting." There were many short-cuts taken by the old-timers. We don't know the context of that short-cut. However, today most rifles are bought wit the intent of shooting targets and hunting. Both endeavors require accuracy. It is true that "accuracy" is in the eye of the beholder and some are satisfied with differing levels of accuracy than I. But most of the folks I know would not be satisfied with a rifle that could not hold a 2 inch group at 50 yards and some expect a 3 inch group at 100 yards. I would be doubtful of achieving that level of accuracy with an asymetrically swamped barrel.

Best Regards,

JMC

erdillonjr · « **Reply #17 on:** August 20, 2009, 04:50:40 PM »

If you send it back to Rice they might be able to swamp it for you. It is worth a phone call. Ed

Roger Fisher · « **Reply #18 on:** August 20, 2009, 06:37:14 PM »

All I can add is that our 'soft' barrels do in fact have a sweet spot upon which said rifle barrel should be rested on rest shooting - bench - stix etc.

Hang said barrel from a wire or cord and tap with a mallet to find the 'dead' spot or do it the hard way as I usually do things. -- Shoot the girl resting said rifle at various spots til you get best groups w/o any wide fliers......I do recall that 'position' is important to your success in many things

JCKelly · « **Reply #19 on:** August 20, 2009, 11:31:47 PM »

Unless it is something like heat treated & double tempered 4140 or 4150, that barrel steel will have some level of residual stress.

So you will need to file the same amount off each side to keep it from bending. Like a little from one side, then a little from the opposite, all the way around.

As a metallurgist, I have known this for decades. But, like the shoemaker's kids, I had to watch a miniature rifle barrel I was swamping suddenly "kink" at the swamped end. Golly Ned I wish I hadn't done that. Bent it back straight again, relieved the stresses with a torch & finished filing the barrel. It didn't have to be accurate, 1/3 scale smooth anyway, but had to at least LOOK straight. You have touchier requirements to keep your barrel accurate.

eagle24 · « **Reply #20 on:** August 20, 2009, 11:40:45 PM »

As I said in the beginning, this is a 7/8" X 40-1/2" .45 barrel. I had in mind a very subtle and gentle swamp to about 3/4" in the waist. Maybe it's not worth the time and effort, but I thought I would ask anyway. I guess I'm just not seeing it being as difficult as most make out that it would be.

Long John · « **Reply #21 on:** August 21, 2009, 03:38:51 PM »

G

A little bit osf swamp AIN'T that hard! And with that subtle a swamp it won't take any where near as long as taking .020" off the entire barrel to get it down to size. Do it! You will be glad you did!

Best Regards,

JMC

bob in the woods · « **Reply #22 on:** August 21, 2009, 03:52:00 PM »

Happy filing. Everyone should do it once. I filed out an oct to round pistol barrel once, from rough stock.
Just wanted to see if I could do it. As long as you're not trying to make money at it, you'll do fine!

T*O*F · « **Reply #23 on:** August 21, 2009, 10:50:45 PM »

I wonder why everyone is mentioning "draw filing" the barrel when it seems that using a lathe way scraper would be more expedient and probably quicker.

Pete G. · « **Reply #24 on:** August 22, 2009, 01:03:47 AM »

Quote from: Long John on August 20, 2009, 04:45:25 PM

Pete,

With all due respect, I must disagree. As you shoot a rifle the barrel will heat up. If the barrel is not symetrical I would expect the heating will cause the barrel to bend toward the thinnest side.

Maybe so. I do have a late percussion with a 15/16" 36 cal gain twist that is built as I described, however. The small caliber, heavy barrel and gain twist all make me think it was built more for shooting than hunting, though. I hadn't really thought about the fact that the swamp may cause something weird to happen, although I would think the uneven heating would also happen in an assymetrical barrel whether swamped or not.

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Author Topic: Barrel Harmonics (Read 11531 times)

eagle24

northmn

Birddog6

eagle24

erdillonjr

eagle24