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Old 07-01-2008, 06:56 PM   #161 (permalink)
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Originally Posted by brycelarson View Post
Thanks for the report on your experience with the backspin bolts. I think other than HP you're the first that has offered personal experience. Based on shooting a bunch of paint with these guys - how great is the expected range increase that you get? Is it on the order of magnitude of the flatline - or more subtle?
One of my teammates in the early 90's had the CopperT bolt for his PMI -3. It took alot of honing of the stock brass barrel to get it to work. I would say that the results were very comparable to a Flatline barrel. However it was rough on paint and would regularly have barrel breaks, so he gave up on using it.
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Old 07-01-2008, 08:06 PM   #162 (permalink)
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Originally Posted by cockerpunk View Post
the only trouble with the "push up against the top of the barrel theory" is this -

any flow around the bottom of the ball, will cause a pressure drop, which intern will cause the net force on the ball to be downward, back into the center of the barrel.

unless the mass flow rate of the air is great enough to impart a force due to its mass, the force cuased by air under the ball will acutally pull the ball down into the center of the ball.

shooting from the hip, im doubting the mass flow rate is great enough.
That's kind of been nagging me in the back of my brain a bit too. Damn Bernoulli . So, how much mass flow rate would actually be needed to counter act the drop in pressure caused by Bernoulli's priciple? May or may not be applicable, but I'm curious anyways.

This will probably come up again if/when someone does accuracy testing with overbored barrels (which I may do myself, as soon as I finish one particular project I promised myself I'd finish before moving to the next). Start with the ball at the bottom of the bore, and combine Beroulli's priciple with inertia, air flows over top of ball, ball lifts towards center, inertia causes ball to lift a bit more, air now flows under ball, pulls ball back down towards center, inertia and gravity pull ball a bit more, air flows over top...wouldn't the ball be making a sine wave down the barrel? Something to ponder for now, sorry for the brief trip off topic.
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Old 07-01-2008, 08:17 PM   #163 (permalink)
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Have you considered that maybe the ball's spin is imparted quickly and is retained through the barrel despite being centered, hence why overbored barrels work better?

Airsoft hop systems spin the pellet at the start of the barrel bore, where it transitions to smoothbore. They work just fine without using the top of the barrel to spin the projectile.
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Old 07-01-2008, 08:33 PM   #164 (permalink)
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Originally Posted by Painthappy View Post
Yup... great job... Maybe we can get some Cooper-T's better bolts for you guys to try out!

Did I mention how much I like this place?? Keep up the great work. Lots of brilliant minds at work here.
I'd LOVE to get my hands on one, and then ask PPS if they can take that bolt design and make me a bolt just like it for my Pyre .

Then use the bolt for that PMI-1 drop-out 12g pump I'd like to do .
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Old 07-01-2008, 08:39 PM   #165 (permalink)
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Originally Posted by russc View Post
Have you considered that maybe the ball's spin is imparted quickly and is retained through the barrel despite being centered, hence why overbored barrels work better?

Airsoft hop systems spin the pellet at the start of the barrel bore, where it transitions to smoothbore. They work just fine without using the top of the barrel to spin the projectile.
good thought man, if something like a hop up were to get the ball spinning the correct direction, I would wager money that it would act to lead the ball along the top of the barrel catching more rotation.. it could be adjustable like an airsoft gun too..
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Old 07-01-2008, 08:53 PM   #166 (permalink)
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Originally Posted by russc View Post
Have you considered that maybe the ball's spin is imparted quickly and is retained through the barrel despite being centered, hence why overbored barrels work better?

Airsoft hop systems spin the pellet at the start of the barrel bore, where it transitions to smoothbore. They work just fine without using the top of the barrel to spin the projectile.
Good point, and I am starting to question whether it's the top of the barrel or not myself, based on a little testing we were doing earlier today.
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Old 07-01-2008, 09:03 PM   #167 (permalink)
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Good point, and I am starting to question whether it's the top of the barrel or not myself, based on a little testing we were doing earlier today.
Anyone have a really rough finished large bore barrel to send Cockerpunk? It would be the ideal barrel if it did push the ball to the top. Or possibly a barrel that's rough at the beginning, then smooth for the rest of the length. Just spitballing out ideas, don't mind me.

I'm seriously tempted to pick up some clear PVC pipe and some pingpong balls and do some experimentation with an air nozzle.
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Old 07-01-2008, 09:39 PM   #168 (permalink)
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Originally Posted by Sir Brass View Post
I'd LOVE to get my hands on one, and then ask PPS if they can take that bolt design and make me a bolt just like it for my Pyre .
Craig doesn't like the Cooper-T bolts for some reason. Awhile back I brought a thusly equipped PMI-1 in to get the Perf Tune, and when I picked it up it had a PPS bolt with the Cooper-T in a separate bag, and he said something to the effect of 'I didn't know if you wanted us to throw it away or if you wanted to'.
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