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spin perpendicular to the travellingpath (magnus effect)

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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spin perpendicular to the travellingpath (magnus effect)

Unread postAuthor: Antonio » Thu Apr 17, 2008 12:47 pm

Would the effect of spinning on a airsoft bb ball make it fly further? By this I dont mean backspin like in the hopup systems, rather a sideways spin like in rifled guns. I know that rifling makes the air flow past the projectile etc, but thats not my question. I am just wondering if this spin would make it more stable, eventhough its round. From my experience, I c bbs fly any direction after 20meters. I think that if this spin is imparted it would resist the ball to spin in a different axis and fly any direction.

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The ball spins in the direction of the red arrow and it travels allong the green line.
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Last edited by Antonio on Sun Jun 22, 2008 2:33 pm, edited 1 time in total.
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Unread postAuthor: dilweed » Thu Apr 17, 2008 1:01 pm

personally i think you have 2 options:
Use a rubber pipe a little smaller than the actuall barrel and load a bb into it, This will create an airtight seal and spin the bb increasing, accuracy, power, range etc. When you see the bb randomly fly is because it is so light, it rapidly looses kinetic energy and speed. With wind, gravity speed and the magnious effect, it will really screw up your bb's flight path. A rubber thingy backspin ( above) will really help.

If you want more power blah blah blah... You really should use rifiling. This is extremely hard as you need perfect or near perfect angled spiralled grooves in your barrel. I would recomend 4-7 seven grooves. Also dont use a bb for rifles. because of its imperfect shape it will: wear down the rifling quickly

may jam

lots of air will flow by it, and it wont grip the rifling and it will SUCK!!

But.... if you use homemade or buy pellets....holy shizel this beast is amazing will be your effective answer. Use a elongated cylindrecal bullet.
carve grooves in it to match the rifiling or use a plastic or foil wrap around the bottom to grip the rifiling. Pentration will grately be improved among constantly repeated other things that i am tired of typing. Also use a hollow or light back and a heavy (lead tip) muskets converted into rifles increased fps from between 500-700 fps to civil war era rifle of 1500 fps. You do the maths hurray. it will be awe inspiring. really. i mean it.

if i had the patience and time i would cut a leg off for a rifled barrel ( just a figure of speech- sorta mean it!) but since you want to use ball shaped ammo please use the first way. airsoft guns use it so the best bet is you should. I am very impressed by your designs and really cant believe your asking this question. youre better and smarter than this, im 13 with A.D.D and figured this S**t out man! i would love to see the results of this and i hope this will increase all us spudders overall pleasure of shooting S**t up!.................................................................................................. lol

peace out, im far out, dilweed....
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Unread postAuthor: jimmy101 » Thu Apr 17, 2008 2:46 pm

Spinning a spherical shell around its axis of flight will not increase range, at least not significantly. For non-spherical shell (ie. a bullet), it does increase the range since the spin keeps the round from tumbling and tumbling increases drag.

The main advantage of firing a round shell from a rifled barrel is that the round has consistent spin. Consistency is key to accuracy.

Generally, you expect all shells to exit a barrel with some spin. From a smooth bore barrel the spin will vary from shot to shot. With spherical ammo, sometimes backspin (which increase range a small amount), sometime side spin (which make the round hook or slice), sometimes frontspin (don't recall the correct term, its the opposite of backspin) which will make the round sink.

A hop up increases accuracy but also increases curvature. A round following a curving trajectory can still be very accurate. The key is that it curves the same way every shot. Depending on the setup of the hop-up it can increase lift, decrease lift or make the shell curve left or right.

A rifled barrel also gives the round (more) consistent spin and increases accuracy.

In addition, a barrel should be properly "crowned" so that the blowby of gases that occurs when the round exits the barrel won't impart spin to the shell.
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Unread postAuthor: psycix » Thu Apr 17, 2008 3:24 pm

Wasnt the correct term for frontspin called topspin?

And yup, jimmy said it all.
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Unread postAuthor: Tom » Fri Apr 18, 2008 9:02 am

Well ant, maybe fabricating your own bullets from molten BB's :D. You can buy some heavier ammo at Dutch air rifle shops online.
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Unread postAuthor: judgment_arms » Fri Apr 18, 2008 9:35 am

Range will not be increased much at all, but accuracy sure as heck will see I nice improvement.
Use the right rate-of-twist and a good patch or sabot and you’ll be putting plastic on target long after every one else’s round ball has hooked way off target.
these at 350-400fps would work best, more mass means more range.
Also, I wouldn’t want to get hit by one of those at 350fps at anything closer than 30 yards…
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Unread postAuthor: Antonio » Mon May 12, 2008 12:07 pm

Thnx for the feedback you guys:)
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Unread postAuthor: POLAND_SPUD » Mon May 12, 2008 4:17 pm

I've shot some 16mm marbles with a ghetto hopup and it turned out that it does increase accuracy and possibly range (well I've only noticed that the marbles flew higher so I had to aim below the target to hit it but I have no idea how much it improved range becasue it's rather difficult to see a marble after it covered 100 m)

It wasn't as accurate as I wanted it to be but I suppose it had somethnig to do with the fact that marbles vary in size so the hopup can't be expected to put consistently spin on them.
I got more less the same accuracy with a hop-up and marbles as I get with steel bolts - not the best result but defienatelly much better than marbles w/o hop-up...

I expect that it could be done much better with well made hop-up and consistent ammo - like for example ballbearnings

@ant spinning a BB like that doesn't make much sense too me... ok it might make it more stable but why would you do that if you can get a rifled barrel and use ammo shaped like normal bullet ?
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Unread postAuthor: Antonio » Tue May 13, 2008 6:49 am

I was wondering at what rpm a bullet has when it leaves the barrel of a rifled rifle. I dont think backspin increases the accuracy of a gun as poland spud said (thnx for you look into the idea). I mean rifling is used on paintball barrels but then in the sense of airporting> does this do anything or is it just a myth?

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