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How do you find the sweet spot on your barrel?

6K views 44 replies 22 participants last post by  biff 
#1 ·
How is the best way to find the sweet spot on your barrel in order to dampen the vibrations to improve the pattern! Biff
 
#4 ·
Ya know I mean this in no homosexual way at all but your are just getting anal about things you think will improve your score but really will not.

BTW ... when you find the spot you will know because it will taste better than all the other spots but be sure to do all tasting after your fire 1 very fast round of skeet.
 
#8 ·
This is a topic which relates to shotgun barrel performance. Vibrations do occur with shotgun barrels as an ounce or more of loose lead pellets travel down this thinwalled tube of steel. Some target rifles have dampers mounted on them to help control the vibrations to improve accuracy and others have tuners on the end of their barrels for accuracy improvement. Some shotguns have barrels a certain length (33" was the length selected by Dennis DeVault for his MachOne) because the results of the patterns were better due to the harmonics produced at different lengths. Maybe feeling the barrel as it is shot would help determine where the vibrational rate is strongest might be the place to add some dampening material. Sorry if this got Mr. Newbie all excited, no offense intended. Biff
 
#12 ·
I thought accelerometers would be just the ticket to test recoil but couldn't make it work because guns vibrate like crazy when they are shot. But since O/U's with full ribs shoot about like single barrels (but it's a problem to make that so I'm told) I doubt if vibration can be the cause of many of our misses.

To ever answer your question, biff, you'd need a gun rest such as Bruce Bowen's. It's a very good
question which no one has published on and would be a valuable contribution to the sport.

Neil
 
#14 ·
Dave, that man in Florida was Jack Seehasse who used to do a type of harmonic balancing. Many people swore what he did worked, but many others said it was just"Smoke and Mirrors"(The latter group would have loved TS.Com!). I used to own a TM1 that Herb Orre did the choke on and Mr. Seehasse did the harmonic tuning on the barrel, I know the patterns on paper were the most perfectly round, tightest, and most uniform shot pattern of any gun I have ever patterned. It was and still is a great handicap gun, I saw a fellow shooting it at the Music City Shoot and when he centered the target, it virtually disappeared!

Dave the barrel on my Ljutic has been cryogenically treated as are the guns from DeVault Industries. Not only that they use no hot welds on the barrels, Dennis knows how to make guns! Biff
 
#16 ·
OK, enough silliness. Neil, can the harmonic vibrations setoff by the ignition of the powder charge move through the metal of the barrel at a speed faster than the speed of sound? If not, then the shot charge would probably exit the muzzle ahead of any harmonic vibrations which, in any case, would be damped by the plastic wad surrounding the shot and be evenly distributed around the charge because the barrel is a cylinder.
 
#17 ·
Neil- You need to broaden your thinking. My gun shoots a fairly tight pattern that has a uniformly random distribution of shot within a 20 or 30 inch circle.

Shotgun barrels do vibrate as the shot charge is traveling down the barrel and after it has left the barrel. But, much more importantly, the recoil also causes my head to vibrate. Now, if I could only find the "sweet spot" on my head and attach a lead weight to that spot I might have something.

Can anyone suggest the proper place for me to stick the lead weight?

Pat Ireland
 
#19 ·
JB, I think you are confusing the idea of "harmonic" vibration with is use in sound but it can occur anywhere unrelated to sound. I guess when people talk about it with guns they really don't mean harmonic at all, but rather the idea that barrels simply vibrate in a sinusoidal wave with one or more nodes.

biff, you cite the BAR barrel device which was intended to be able to "tune" a barrel for a particular load. Deutsche Waffen Journal did a test of it and got nowhere, but a Wisconsin benchrest shooter claimed it worked, supported primarily by an article in a advertising magazine which was totally worthless. I sometimes go to a local club on sight-in day before deer season to lend a hand and for a while lots of guys had BAR Brownings. I never saw anyone get close to figuring it out though none ever really tried to either and seemed to be doing little other than wearing out the threads, twisting them one way, then another, then back again. Yes, the POI did move, I guess, but whether it was something you could do anything with was never demonstrated to me.

I talked with Jack Seehase many times, in particular with reference to the yellow handout he distributed at the Grand in the late 80's. It held that the atmosphere had _nothing_ to do with the fact that shot spreads and rather that it was _all_ barrel vibration. He provided a formula to prove it, but would never say what what each of the elements - say the variable "z" - stood for. I never believed a single word of it.

I did test two TM-1's he did for a couple of vets. The patterns were very tight, just as you say, but that era TM-1's shot very tightly from the factory and I personally doubted anyone could tell the difference, if any. Were the Seehase guns good shooters? Yes indeed; terrific I'd say. Just like the stock one in my safe.

Neil
 
#20 ·
Neil, Tuners do work well for 22 rimfire benchrest shooters. You have no control over your velocity of rimfire ammo and thats where the tuner comes into play. On the other hand when shooting centerfire you can control velocity. I have a match Anschutz with a Hohen tuner on it and I did see a slight improvement before and after.
 
#21 ·
TM251, I'd have thought that with something like Tenex you have near-perfect control over velocity and in such a case, as well as the kind of work a benchrest shooter is willing to expend, an improvement is attainable. However a hunter, shooting a few shots in an afternoon, is not likely to get much out of one; at least that's what I saw.

But with shotguns velocity is constantly changing even (of especially, speaking in terms of lot-to-lot) if you shoot factory. As once it's tuned for lights what happens when you go to 3-dram? Or one-ounce? Or different powders? And so on.

There's a general assumption that shotguns shoot in the same place shot after shot. They don't. Just a with a rifle, the POI of a shotgun is a pattern. I doubt anyone knows how large that pattern is or what its determinants are, but I'm thinking it's a lot bigger than generally recognized. A lot.

Neil
 
#23 ·
I think that might be exactly why he asked because even thinking that barrel weights and such hanging on your barrel with effect your patterns is about as analy idiotic as thinking that with this new weight on the barrel how it will now effect your swing and make you miss a target because of screwing up your swing and then when you make some sort of correction for that then something else because of that correction and its a never ending course of this and that to justify why your missing a target here and there instead of just ... well who in there right mind would ever question missing a target because of balanced harmonics of the barrel and that weight could be inserted ... heck ... Pat melt it and use it for shot.
 
#25 ·
Neil, I have missed all this as I had a good nights sleep and wake up to the interesting discussion that went on as I slept! And now they are attaching weights to Pat's head!

My term Tight and Uniform, in my mind meant it was a neat tight round pattern where the shot was evenly distributed over the whole pattern. I think that is what I was trying to say. Funny thing is I've owned that gun, nicknamed "Old Rusty" twice and if I have a chance to buy it again(the fellow who owns it now doesn't want to sell it) it will be a keeper for the back of my safe!

Neil, I'm glad to hear you say shotguns don't shoot in the same place shot after shot. They are a smooth bore and have a thin wall for the shot to travel down,kinda like my old Red Ryder BB gun, and I'm sure with all your testing you have seen variations form many different things affect your test results! Thanks for joining this discussion and I won't mention Cryo treating the barrels for keeping the POI the same as "the eye rolling" group will go crazy! Biff
 
#26 ·
Neil,

My reference was to the fact that if the shot charge has accelerated to anything over 1125 fps muzzle velocity, I suspect that it overtakes and runs ahead of the barrel vibrations caused by the discharge.

As to POI changes, I also suspect that as hot as a barrel gets in a round that heat distortion would be a far more logical explanation than barrel vibrations.

OTH, we are shooting a pattern that is the size of an elongated trash can lid and putting the center of that pattern at the right spot ahead and above the target will result in breaking the target something north of .999%. As such, every shooter walking the face of the earth should be more concerned about doing that everytime rather than the sine waves in their barrel.
 
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