AmericanLongRifles Forums
General discussion => Black Powder Shooting => Topic started by: Short start on April 05, 2014, 07:19:44 AM
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In airsoft, a sport like paintball but using smaller plastic pellets, there is an innovation called "hop-up". A piece of rubber protrudes into the bore very slightly and puts a backspin on the outgoing BB which causes it to fly straighter for longer.
An idea I had was to try double patching the top of a ball in a smoothbore to achieve this spin. Has anyone experimented with something like this? I've heard of bending barrels to achieve a backspin, but that sounds iffy.
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Is that anything like backspin on a golf ball to make it "fly" longer"?
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I think if you want to "achieve spin" you use a rifled barrel.
The method you describe may impart some spin but how would you control the consistency?
Unless you could duplicate it exactly for each shot the point of impact would be erratic at best.
That is why you work up a load/patch/ball/lube combination and stick exactly with that - so that you know with some certainty (or as certain as you can be) where the ball will impact at a given distance.
So maybe if you are horsing around punching paper you might fiddle with something such as this "just to see" what it does, but if you were shooting at game you owe it to your quarry to develop a consistently accurate combination that will allow you to impart a kill shot - you don't want to end up with a "curve ball" that only ends up wounding.
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Seems to me there has been a lot of effort expended in trying to avoid what you are trying to accomplish in round ball flight. But go ahead on, and let us know what you determine.
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Go ahead an try, nothing ventured,,,.
The different dynamics of the air soft pellet mass and it's velocity vrs a lead ball even at low charges is huge.
If I remember correctly, the military of several countries spent many decades trying to improve the accuracy and range of their infantry guns in the 17th, 18th and early 19th centuries.
But what da heck, you might find something they over looked.
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Hop up is the equivalent of putting massive back spin on a table tennis ball. I never understood the mechanics of it, but it has the effect of generating lift, and the light ball simply soars, travelling much further than you would get with a straight on hit.
Air soft pellets are light and small, a disastrous combination in ballistic terms. The idea of hop up was and is simply to get a bit more range out of the things.
I can't even imagine how much back spin you would need to make a heavy lead ball soar.
Just as well lead balls have better ballistic properties ;D
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I don't understand how a patched ball can rotate that way?
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While your at it, why dont you devise a method to consistantly dimple the surface of the roudball too. ;D
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Why do you think this would work? The rifling already puts an clockwise spin on the ball. If you could accomplish what you wanted to do, you would disrupt the spin of the ball.
Maybe it would work in a smoothbore if you could devise a way to hold one end of the patch (it would have to be a strip) at the end of the barrel and as the ball leaves the barrel the rest of the patch (strip) would somehow create a backspin.
One part of the patch has to be held in place in order for it to create a backspin.
I think any patch material would be torn to shreds doing what your thinking about.
I consider it an effort in futility. But hey, who knows maybe your onto something.
Centershot
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I personally don't understand the need for all this. Back before the Civil War some guys tried to improve the range and accuracy of smoothbore muskets, even including adding wooden sticks with fins (a la rockets) and nuthin' worked. A big part of shooting these things is learning to shoot them well in spite of their ballistic shortcomings and overcome them by practice and working up loads that make the most of the barrels. If you want to impart spin to a projectile you simply rifle the barrel or use a rifled slug.
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The military's of the world found by swaging or casting the ball closer to the bore size (reducing the windage), although increasing loading problems due to the buildup of fouling with fewer shots, it also increased the musket's accuracy. Thus, they found, as we know today, a tighter fitting ball increases smoothbore accuracy.
Attempting to somehow improve smoothbore accuracy by causing a spin is easy - use VERY coarse emery or flint paper and scratch a spin into your bore- right or left twist, doesn't matter. You can use another rifled barrel blank as a 'guide' - easy to do.
This method actually works fairly well for a number of shots before needing to be reapplied - Dan has mentioned this method here at ALR as possibly being used to day, and definitely was used many years ago.
This method might be construed as a move outside the flavour of good sportsmanship (by mechanical advantage, seeking unfair advantage in competition) and thus would/should remove that smoothbore from a smoothbore event, I'd expect.
If improved accuracy was desired from your favouite stock design, by all means - put a rifle barrel on that gun, saving the smooth one for shot.imho
Or - you might use a centre-punch and "punch" a DIVOT staight down from 12 o'clock into the bore at the muzzle or very near the muzzle. This "might" impart a backwards spin to the ball - however slight, which might cause it be more stable than normal and not take on the normal 'knuckle-ball' effect which badly effects accuracy, sooner or later depending on the velocity. If it worked, would it be a 'cheat' in competition? It just might improve a smoothbores accuracy for hunting, as well as having no adverse effect on shot patterns.
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do rifled slugs actually work in shotguns? ???
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sent you a PM, LH
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Thanks Daryl, interesting stuff. On the smoothbore, what would filing the barrel off out of square to the bore do? Maybe impart some spin? Seems like any spin other than around the axis of the line of flight would cause the ball to fly on a curved path? I guess if it was a uniform curve it might be usable.
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As I understand it, when the muzzle face is not square to the axis of the bore, the gases will escape earlier on one side than another, and while this can push the projectile off course, I don't see why it might cause a spin.
I think that those of us who are less than totally conversant with maths and mechanics can overthink questions like this very easily. Right now I'm wondering why normal rifling induced spin doesn't cause the ball to follow a sideways curve :o
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do rifled slugs actually work in shotguns? ???
I've never used one so I can't say. I have been told they do, some better than others.
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DaveP, As a spinning rifle projectile falls through the air due to gravity, it does drift sideways--to the left in a right twist rifle, and to the right in a left twist barrel. At very long ranges, this drift is significant. When shooting North or South in the Northern Hemisphere with a right twist barrel, this drift helps to cancel the Coriolis drift effect. The principal is the same as a pitched curve ball. This has to do with the air on one side of the projectile speeding up because of the twisting, and slowing down on the other side as the ball passes sideways to its spin axis through the air due to gravity. In baseball, the pitcher spins the ball sideways to the direction of flight, causing the ball to curve left or right or up (or potentially down), depending on how he spins it. Like and airplane wing, the faster air has lower pressure effect on the ball than the slower air, thus the ball is pushed toward the faster air. Some military rifles with very long range sights (like my trap door .45-70) have a built-in cant to the long range sight to compensate for the drift.
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As I understand it, when the muzzle face is not square to the axis of the bore, the gases will escape earlier on one side than another, and while this can push the projectile off course, I don't see why it might cause a spin.
I think that those of us who are less than totally conversant with maths and mechanics can overthink questions like this very easily. Right now I'm wondering why normal rifling induced spin doesn't cause the ball to follow a sideways curve :o
Yes, if the crown of the muzzle isn't square, it'll throw the ball off. The only way to produce a backspin would be to slow one side of the ball down. But to do that there'd have to be a hump or dimple and I think that would have the same effect as a damaged crown. I suppose if there was a way to do this near the breech but after passing that point a bare ball will still be "balloting" down the barrel and will go in the opposite direction of wherever it last contacted the barrel. If the ball was patched, either when loading or more likely when firing, a dimple would likely badly scuff or tear the patch.
I've wondered about the effect of rifling myself over the years. The old Ordnance Department tests with the new Minie rifles mention this. There is some lateral drift in rifled arms and from what I've read drift is liable to be greater when the twist is tighter. I'm sure there are other opinions on the matter. Gravity would overcome upward vertical drift and compensating for drop would take care of downward drift.
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If a ball is spinning left to right on top it should be spinning right to left on the bottom, wouldnt that negate any drift in one direction? Don't know but am wondering as this has come up in conversation before.
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Since the projectile is falling due to gravity, and with a right hand spin (clockwise as seen from behind), the air on the left side of the projectile is pulled up by the spin and "up" by the downward travel of the bullet. The air on the right side is pulled down by the spin, partially canceling the "upward" air due to the fall. So the air on the left is faster and on the right is slower. So the ball moves to the left.
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LH,
IMHO you are way off base with your thinking. First, bending a smooth bore barrel is done to change the POI, windage and elevation, not to make the ball spin. Second, filing the muzzle off center is going to do the same thing, change the POI, due to gas escaping from the muzzle at a different than square angle. File the left and it will push the ball right and vice versa.
Mark
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Bill, Thanks for explaining that point. I must confess, the thought only came to me while I was typing, my comment was ever so slightly tongue in cheek. Nice to realise it wasn't a completely dumb idea :)
The club range only extends to 100 yards, and as I find that an adequate challenge for offhand shooting I have tended to ignore long range issues.
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The muzzles on some American Double Rifles of the 1800's were filed to produce/induce regulation. The outsides of the barrels were filed to bring the 'balls' together, or filed from the inside to outside to spread the impacts. Filing top or bottom will also influence the point of impact.
A MODERN double rifle firm called "Sabatti" 'used' to used filed muzzles or angled crowning to regulate their modern double rifles. this received a LOT of bad press in some double-gun forums and now Sabatti is now apparently regulating the barrels before finishing them as is normal for high quality double rifles.
The reason for saying this about Sabatti, is to show you that a ball's or bullets poi can be altered by filing the muzzle - whether on purpose or not.
Gas escaping from one side, top or bottom before the opposite side, will tend to direct the projectile in the opposite direction of the gas's first escape - thus, this system does and has worked - but is NOT recommended. This could be used to 'regulate' a smoothbore that needs correction and the owner does not want to bend the barrel to achieve it.
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To get away from "knuckling" in my .540 smoothbore, I've jacked up the charge from 60 to 80 grains of 2f. Shoots point of life size rabbit(gong)@100 meters.Tight ball/patch/lube/barrel combination is the first item to get correct.Then I started experimenting with charges. With 60 gr. at 25 I got three shots touching with 2 fliers,not good enough. With eighty grs., she brought them all together. My ball size is .513(a .510 mold that casts oversize perfectly)and a .030 tight woven Carhart type denim. Gives me 15-18 thou compression around the ball. Spinning a ball in a smoothbore sounds oxymoronic to my taste for smoothy fun. If they were made smooth,I shoot 'em smooth.JMHO.
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Good responses. I would use this for target shooting and in the interest of science.
I only have rifles so I can't really try for myself yet.
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I remember many many years ago there was a magazine article about a guy who rolled the ball on a rasp to get little spikes all over the surface. The idea being that it would fly straighter. After leaving the barrel with a whistling sound it veered left, conitued over cattle in the next field, sending them into a panic, then came round behind him. He ducked just in time and the ball continued on and struck the target. He was disappointed because it hit the edge and he had been aiming at the centre. Put it down to the rasp marks being uneven on one side.
Then there was the story of the guy who accidentally cut off his nose one night during a power failure. Don't know if we are talking about the same person here. Phoned the doc who rushed over and managed to sew it back on. When daylight arrived the man found to his surprise that, in the dark, the doc had sewed it on upside down. He learned to live with it until years later when he was caught out in a downpour without his hat and drowned.
Its a strange world.
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Musta used a Nicholson#49. The #50 would leave too small of dimples for the human ear to hear the whistle! :o :o
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Lol hammer
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Thanks Daryl, interesting stuff. On the smoothbore, what would filing the barrel off out of square to the bore do? Maybe impart some spin? Seems like any spin other than around the axis of the line of flight would cause the ball to fly on a curved path? I guess if it was a uniform curve it might be usable.
If an undersized ball is projected from a gun's bore - it will take on spin - probably not the same each time which is why smoothbores with loose fitting balls are inaccurate.
A crooked muzzle will project the ball towards the opposite side to the minor angle. I cannot see that giving a spin to the ball - it might - or not - probably not - who knows? If it did, would it be the same each time? What if the ball exited already spinning in a different direction? could it be reversed - doubt that too. How many fairies can dance on the head of a pin? I think this type of hypothesizing is quite similar to that age-old question about the trinkets (fairies). No offense meant, LH.
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Is that anything like backspin on a golf ball to make it "fly" longer"?
Backspin is imparted by the loft of the club to provide elevation and counteracts side-spin which is usually the result of swing error (unless intentionally used as by advanced golfers (fade/draw) to counteract wind and course conditions.)
If elevation could be applied to a golf ball by another means, there'd be no need for backspin. IOW you can't hit a ball properly with a golf club and not induce backspin. That's just how it works.
A (golf) ball without dimples, floats and flutters like a knuckleball. The spin, although imparted by the club as before, doesn't "get traction" without the dimples. Just like a baseball without seams wouldn't curve.
Airsoft? no clue. is there rifling?
back to powder and lead yo.
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If you want your ball to spin, shoot a rifle!
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Thanks Daryl, interesting stuff. On the smoothbore, what would filing the barrel off out of square to the bore do? Maybe impart some spin? Seems like any spin other than around the axis of the line of flight would cause the ball to fly on a curved path? I guess if it was a uniform curve it might be usable.
The filing of muzzles "off square" was a method used in the 1800's by Colt to 'regulate' their side by side rifles. It was also used recently by a modern double rifle gun builder in Europe, however they have ceased to do this and are now regulating properly by moving wedges between the barrels.
As noted, filing off square will allow powder gases to push the ball or bullet in the opposite direction to that side the gasses escape from. I doubt very much escaping gases would cause any spin on a ball as it exits.
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Is that anything like backspin on a golf ball to make it "fly" longer"?
If elevation could be applied to a golf ball by another means, there'd be no need for backspin. IOW you can't hit a ball properly with a golf club and not induce backspin. That's just how it works.
A (golf) ball without dimples, floats and flutters like a knuckleball. The spin, although imparted by the club as before, doesn't "get traction" without the dimples. Just like a baseball without seams wouldn't curve.
Airsoft? no clue. is there rifling?
back to powder and lead yo.
I suggest you do a little searching for the physics of ball flight. Backspin creates loft.
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Mate I have a dozen or so 1/16 scale rc tanks, tigers, panzers, they have the hop up system, I thougt it refered to the chute arangement that recharges the main gun with ball. by the way they put dents in the fridge and the dogs are not to keen on them either.
I have found patched round ball fired from a Pat 42 smoothbore shot well enough to kill rabbits out to 50 odd yards. ;D
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I had a .44 smoothbore flint gun that was tremendous on rabbits (head shots only, count) out to 50yards, AFTER Taylor converted it to cap-gun for me. Until it was converted to cap, I made a lot of 3' to 4' long rabbits - but only if they were facing to the left - right hand shooters flinching, shoot low right!
IIRC - I loaded it with 45gr. 2F and a tightly patched .433" ball. It was MUCH more accurate than my current .62smoothie - however THAT one is flint. :D
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The effect of the spin from the Magnus effect is seen with golf balls, baseballs, and lots of other things. The idea in gunnery is that a bare ball is given spin by contact with the barrel and one uses just enough bend to make the top of the muzzle the last point of contact of the ball with the barrel. It has the effects I mentioned:
- It gives the ball a consistent spin, eliminating the variability of spin from random contact with the barrel or from the knuckle-ball effect on an initially non-spinning ball.
- It orients the spin so the effects are in the vertical plane of the trajectory, with no lateral deflection.
- It produces back-spin, which gives the ball lift, and thus a flatter trajectory.
This was first seriously investigated by Benjamin Robins, and described in his New Principles of Gunnery in 1742. As cited at http://www.napoleon-series.org/military/organization/c_velocity.html (http://www.napoleon-series.org/military/organization/c_velocity.html): "Robins also investigated lateral deflection of high-speed projectiles. He set up a series of evenly spaced paper curtains that allowed him to measure the enormous deflections of a musket ball in flight. In one test a ball measured over a range of 760 yards deflected more that 100 yards to the left. Robins identified that it was the spin of the ball that caused this deflection. In a further experiment he bent a gun barrel a few degrees to the left. Although the bullet initially moved towards the left, eventually it reversed its later direction and crossed to the right of the barrel (this effect, which can be observed in baseball and tennis balls, is known as the Magnus effect)." I don't have the reference any more, but I'm fairly sure I remember him specifically writing of the possibility of this muzzle-bend in a "gun" (i.e. smoothbore in British usage) intended for ball, and of this being used by gun makers back then, just as this effect is used today in airsoft guns. Obviously, this bend will throw the pattern low if shot is fired from the barrel.
If a ball is fired without spin, it appears to be essentially a knuckle ball and eventually break in a random direction, just like a baseball. Patched balls appear to be commonly launched without spin, while unpatched balls may or may not be, depending on the specifics of wadding and loading technique. The important questions for a shooter are how far downrange does the ball get before it starts to break and how fast does it diverge after it starts to break. Concerning the first aspect, many smoothbore shooters have reported getting their best accuracy with patched balls, usually tightly patched, at comparatively high velocities, so I suspect that suspect that pushing the ball hard gets it further downrange before it starts to break.
Another possibly related factor is the turbulence encountered at transonic velocities. This factor affects all projectiles and is significant enough that modern long-range shooters seeking the best accuracy try to use a cartridge/load that will keep their bullets supersonic all the way to the target. Here again, a higher velocity will move the subsonic transition further downrange. This turbulence may affect the onset and/or magnitude of the knuckle-ball break, but even if it does not directly affect the break, it will compound with it to increase dispersion (and wind drift IIRC) at ranges beyond the transition. This is also why those seeking the best shorter-range accuracy may choose to use a muzzle-velocity below the speed of sound - match-grade .22RF ammo, for example - to avoid this turbulence.
I haven't seen enough comment about the second knuckle ball aspect - the magnitude of the break - to make any observations concerning the effects of velocity.
Regards,
Joel
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Good points Joel. Indeed,how far down range does the ball get before it 'breaks'.
I've watched, through my the binocs many times as smoothbore and rifle shooters shoot at our '90yard Fox" steel target. When the sun-light is good, I could actually see the last 20yards or so of the flight in my 'birding' binos. The balls from all rifles are predictable in flight- shallow arc to the fox- hit.
From the smoothbores, sometimes the the balls arc onto the fox moving in a perfectly straight line- a perfect shot merely showing more rise and drop than the higher speed rifles, with no windage error. At other times the ball takes on a curve like a trumpet's horn - seemingly flying straight at the fox, then zipping down, up, right or left like curve, climbers, drop balls.
I should note that the incredible display of curve balls happens more often with one particular shooter, who only uses 65gr. 2f in his 20 bore guns, thus his velocity is probably well under 1,000fps to start with. The other fellows who shoot more powder in their 28 and 20 bores, have less 'curve' balls, indeed, they pretty much all shoot their smoothbores more accurately than the light load shooter.
I have never observed the typical knuckle ball up and down motion seen with baseballs. Perhaps this isn't happening with these faster moving balls, or perhaps the up and down undulations are so spread out over distance (slowly acting) that they cannot be observed over that relatively short 90yard distance.
What I've found in my own smoothbore, is the more powder I pour in, the better my long range shooting becomes - thus, the further the ball seems to get out there relatively accurately, before it does weird things.