Big John
45 Cal.
Shooting a 28ga. smoothie, how much does a thin barrel causing whip play in accuracy ?
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Barrel Whip
- Thread starter Big John
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paulvallandigham
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If you are talking shooting RB, then a full length round barrel will have lots of barrel harmonic waves. That is why a half octagon/ half round barrel is so often seen on these guns. The rear half of the barrel is strengthened by the Octagon portion where the chamber pressure is the greatest, and the collective combination of triangular shapes created by any octagon helps to dampen harmonics. When the ball reachs the round barrel, the harmonics are smaller and affect accuracy less.
Master Blaster said:
On the micro scale there is a lot going on in any barrel much less a thin barreled smooth bore when it is shot. With the right instruments you can measure deflections in every direction that would make you cringe. But, the practical reality is that the motions you input to the barrel when shooting are so much greater than those inherent in the metal that the result is basically none. At least that is my experience. :hatsoff:
arcticap
54 Cal.
I load using a .520 PRB and only a very moderate powder charge because it seems to work the best.
So the combination must not be creating much barrel whip I guess.
But when it comes to shot I load it up to the max! :wink:
So the combination must not be creating much barrel whip I guess.
But when it comes to shot I load it up to the max! :wink:
Russ T Frizzen
70 Cal.
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That's an important point. Trying to drive a ball at rifle velocities from a smoothbore isn't going to help accuracy at all. A fairly tight patch and ball combination over a moderate powder charge works best and may help to reduce harmonics. I've found that a four to one ratio of lead to powder is about maximum in a smoothbore and even less powder is often better. I don't have a chronograph at the moment, but I have a feeling that 1100 f.p.s. or so is about the ideal velocity in a smoothbore. Perhaps Paul or someone will weigh in on this?
paulvallandigham
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I tend to agree with Russ T. Frizzen: 1100 fps is the rough Speed of Sound, or Sound Barrier. Trying to fire a RB at speeds in excess of the Speed of Sound creates all kinds of problems, beginning with increased " Barrel Whip " or harmonics. Its one thing for the barrel to deal with light weight gases expanding at more than the speed of sound. Its quite another for it to deal with a heavy RB being pushed over the speed of sound. All that energy has to go somewhere, and in the barrel, it causes the barrel to vibrate. The faster the ball is pushed, the more violent the vibrations.
The old " Rule of thumb " of 1:4 powder to ball weight is a pretty good one. Now, having said all this, remember that FULL Octagon Barrels, like we have seen being discussed recently here on the forum that are often replacement barrels for the T/C rifles, are much stiffer barrels , and will Vibrate LESS. They will always vibrate, but that octagon barrel adds not only diameter to the barrel, but those " corners" or, as I like to see them, a series of " Triangles", as mentioned above. The triangle is the strongest geometric shape we know.
In those FULL OCTAGON barrels, it is possible that you can use much heavier loads shooting RBs without the problems of barrel harmonics getting out of control. However, the problems that such large balls have in the air, once they leave the barrel, with the sound barrier causing problems with sine waves, off both the nose and the back of the ball, the vacuum that is created at the rear of the ball, the real problems of the air rushing into that vacuum to fill it, all while the drag factors are slowing the ball down.
None of these forces are foreign to anyone who has every hit a ball with a baseball bat. You may not " see " them, but you certainly feel them through the handle of your bat as you swing it to hit the ball.
What we have learned since the advent of chronographs is that there is a zone of velocity from 1000 fps to about 1250 fps, where air does all kinds of unpredictable things to balls and bullets. If the ball stays at or under 1100 fps, you avoid all those problems. That is a lesson used by the Slug Gun Shooters at Friendship, when possible, too. At the relatively short ranges that traditional ML rifles and smoothbores are used, this lower velocity is NOT a handicap.
This is something that Toby Bridges, for instances, apparently does not understand, or refuses to understand out of his own financial interests.
The old " Rule of thumb " of 1:4 powder to ball weight is a pretty good one. Now, having said all this, remember that FULL Octagon Barrels, like we have seen being discussed recently here on the forum that are often replacement barrels for the T/C rifles, are much stiffer barrels , and will Vibrate LESS. They will always vibrate, but that octagon barrel adds not only diameter to the barrel, but those " corners" or, as I like to see them, a series of " Triangles", as mentioned above. The triangle is the strongest geometric shape we know.
In those FULL OCTAGON barrels, it is possible that you can use much heavier loads shooting RBs without the problems of barrel harmonics getting out of control. However, the problems that such large balls have in the air, once they leave the barrel, with the sound barrier causing problems with sine waves, off both the nose and the back of the ball, the vacuum that is created at the rear of the ball, the real problems of the air rushing into that vacuum to fill it, all while the drag factors are slowing the ball down.
None of these forces are foreign to anyone who has every hit a ball with a baseball bat. You may not " see " them, but you certainly feel them through the handle of your bat as you swing it to hit the ball.
What we have learned since the advent of chronographs is that there is a zone of velocity from 1000 fps to about 1250 fps, where air does all kinds of unpredictable things to balls and bullets. If the ball stays at or under 1100 fps, you avoid all those problems. That is a lesson used by the Slug Gun Shooters at Friendship, when possible, too. At the relatively short ranges that traditional ML rifles and smoothbores are used, this lower velocity is NOT a handicap.
This is something that Toby Bridges, for instances, apparently does not understand, or refuses to understand out of his own financial interests.
Grizzled Roberts
54 Cal.
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I suppose gentlemen, that it comes down to which load works best in your .54 smoothbore In my .54 smoothbores I shoot 80 grains of 3F. When I first
got these smoothbores I took them to the range and tested loads starting at 50 grains. I went up in 10 grain settings until I found the load that worked best in my guns. I use the same powder measure when shooting at 25 paces and 140 yards.
Both of my .54 smoothbores have Long Hammock barrels. The round part of the barrel is thicker
than most smoothbore barrels I have seen. Perhaps this is why my guns shoot well with a heavier charge. I just know it works.
:v
got these smoothbores I took them to the range and tested loads starting at 50 grains. I went up in 10 grain settings until I found the load that worked best in my guns. I use the same powder measure when shooting at 25 paces and 140 yards.
Both of my .54 smoothbores have Long Hammock barrels. The round part of the barrel is thicker
than most smoothbore barrels I have seen. Perhaps this is why my guns shoot well with a heavier charge. I just know it works.
:v
Russ T Frizzen
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Some years ago, I had a nice little 28 bore fowler (.55 caliber) with a 46" barrel. It had a breech just over 1' across but tapered very quickly and was about .70" at the muzzle. With it came a .525 mold and a 2 dram measure. I never chronographed the load, but it shot into 4" at 50 yards if I was having a good day and that is as far as I would ever shoot at a deer with that load anyway. This worked out to a 4 to 1 ratio load, though I doubt that I realized it at the time. I did try heavier charges but accuracy went away so it was pointless. This was a true fowler and had no rear sight, so long shots weren't on the agenda anyway. Your thick barrel walls may be working in your favor but I don't think any of my smoothbores would be good for much at 140 yards.
Grizzled Roberts
54 Cal.
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Most of the trail walks I attend, you wind up shooting the rifle targets with your smoothbore
so long shots are the norm. At Friendship on the smoothbore sillywets the bears are set at 120 yards at least. I always practice at 100 yards or better for these matches. I of course still shoot close up it the same powder but different sight picture. :thumbsup:
so long shots are the norm. At Friendship on the smoothbore sillywets the bears are set at 120 yards at least. I always practice at 100 yards or better for these matches. I of course still shoot close up it the same powder but different sight picture. :thumbsup:
