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Old 02-05-2013, 05:58 PM   #31 (permalink)
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A few of thoughts to add;

On an over-bored barrel the round should at least be bumping into the sides as it goes down the bore. If not, I would use that barrel anyway. When it bumps, it will be bumped to twist with the rifling. I don't see how you would not get some rotation.

Any rotation from the barrel is a jump start and should be a good thing if the round can stand it. Too much rotation (more than the angle of the fins) should be wasted unless you have a muzzle condition, which is next...
Thie issue is the material's shear strength is very low, so when it bumps into the rifling, it is more likely to shear off the polystyrene than it is to impart spin. (This is of course my opinion, not backed with facts.)

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Porting and barrel length should matter (if any of this does). On a short bull barrel (no porting) the gas escapes forward of the round, which should at least delay the establishment of air flow over the fins, if not push them the other way. With the right amount of porting and barrel length, the round can exit with little or no blow-by.

Yes? Da? Si? o no?
Yes, and I had not thought about the porting/bull barrel... I think we need to send some barrels to Punkworks, as they has access to a high frame rate camera. We should be able to see the difference in spin up times if the porting does what you theorize it will.

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Last edited by tymcneer; 02-05-2013 at 06:08 PM. Reason: Had a DUH moment
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Old 02-05-2013, 10:51 PM   #32 (permalink)
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Quote:
Originally Posted by Spider! View Post
A few of thoughts to add;

On an over-bored barrel the round should at least be bumping into the sides as it goes down the bore. If not, I would use that barrel anyway. When it bumps, it will be bumped to twist with the rifling. I don't see how you would not get some rotation.

Any rotation from the barrel is a jump start and should be a good thing if the round can stand it. Too much rotation (more than the angle of the fins) should be wasted unless you have a muzzle condition, which is next...

Porting and barrel length should matter (if any of this does). On a short bull barrel (no porting) the gas escapes forward of the round, which should at least delay the establishment of air flow over the fins, if not push them the other way. With the right amount of porting and barrel length, the round can exit with little or no blow-by.

Yes? Da? Si? o no?
If you look at the following video, it appears that the overwhelming mass of air is exiting straight down the bore. I believe this to be the case because the aperture formed around the projectile has a total area larger than the ports combined at any point along the barrel's length. Since this aperture is inline with the direction of the gas, this becomes the path of least resistance.

http://www.youtube.com/watch?v=Ea1fdCp-MCg

So, it remains to be seen just how much length and/or porting would be required to negate blow by and, allow for FS spin up.

One reason you don't want the rounds bouncing off the side- they may tilt. (tail wobbling side to side).
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Unfortunately all of you have played the one "speedball" game of paintball for so long you can't conceive of other ways to do this and hence any new ideas seem stupid.
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Old 02-05-2013, 11:00 PM   #33 (permalink)
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Originally Posted by uv_halo View Post
If you look at the following video, it appears that the overwhelming mass of air is exiting straight down the bore. I believe this to be the case because the aperture formed around the projectile has a total area larger than the ports combined at any point along the barrel's length. Since this aperture is inline with the direction of the gas, this becomes the path of least resistance.

So, it remains to be seen just how much length and/or porting would be required to negate blow by and, allow for FS spin up.

One reason you don't want the rounds bouncing off the side- they may tilt. (tail wobbling side to side).

Is there a ball in that video?

I wasn't saying you do want the rounds bouncing in the barrels, just that if you over-bored to that point it should hit the sides at various points and should rotate at least a little on any rifling, even if it looses parts like a target in fruit ninja. Not that a little early rotation is worth significant damage to the round.
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Old 02-05-2013, 11:11 PM   #34 (permalink)
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Proteam Armson barrels have the most prominent rifling I've ever seen. I actually own a 10" Cocker threaded one.
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Old 02-06-2013, 09:36 AM   #35 (permalink)
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Proteam Armson barrels have the most prominent rifling I've ever seen. I actually own a 10" Cocker threaded one.
My single shot pirate barrel is rifled (Armson). I didn't plan it that way, but maybe I got lucky.

What is the best way to acquire some FS rounds, considering price and condition? It looks like the 8 round tubes are considerably more per round than the larger bulk packs (as usual), so what is the smaller practical package?
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Old 02-06-2013, 10:11 AM   #36 (permalink)
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$40 for a 100 round box is the cheapest you're going to find.
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Old 02-07-2013, 12:10 PM   #37 (permalink)
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$40 for a 100 round box is the cheapest you're going to find.
Check eBay hustle Pb has 200 for 79.00 free shipping.
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Old 02-08-2013, 12:24 AM   #38 (permalink)
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Old 02-13-2013, 09:25 PM   #39 (permalink)
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Does anyone know if the inventors of the FS round tried straight fins?

I have a suspicion that spinning the rounds with angled fins does not do much... and that the rounds go straight more because they are like a badminton shuttlecock than a spinning bullet.

Which means that if the fins were straight, the FS round would probably have less drag.

I have also never seen a shuttlecock with angled fins. Yet shuttlecocks don't need to spin to fly straight.
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Old 02-13-2013, 10:16 PM   #40 (permalink)
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Does anyone know if the inventors of the FS round tried straight fins?

I have a suspicion that spinning the rounds with angled fins does not do much... and that the rounds go straight more because they are like a badminton shuttlecock than a spinning bullet.

Which means that if the fins were straight, the FS round would probably have less drag.

I have also never seen a shuttlecock with angled fins. Yet shuttlecocks don't need to spin to fly straight.
Is this the right thread for this conjecture?
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