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-   -   Rifling (http://www.mcarterbrown.com/forums/first-strike/225059-rifling.html)

tymcneer 02-01-2013 01:47 AM

Rifling
 
I wish to start a discussion regarding First Strike and rifling.

Based on video posted by PunkWorks

http://www.youtube.com/watch?v=SqI0WE0z2JA

Starting at 0:45, you can see that the round doesn't start to spin up until after it has left the barrel.


As noted by UV_Halo in this thread: http://www.mcarterbrown.com/forums/f...-not-lube.html

The polystyrene shell has a very low shear strength.

Taking these two pieces of information into account, I would suggest that rifling will improve both accuracy, by reduction of the initial wobble, before the round spins up, and range, by not using up kinetic energy, converting it into rotational energy.

Thoughts on:
- Twist rate
- Style of rifling
- Anything else that seems relevant to the conversation.

Ty

Brassballs 02-01-2013 02:32 AM

The fins on the FSR function the same as fletching on an arrow.
I'd think a rifled barrel would do little to nothing(at best) to improve the flight and distance plus it could possibly damage them.

Cheeserocket 02-01-2013 02:36 AM

The video doesnt say what kind of bore it was, would a .695 id make it spin before it leaves the barrel? or would it be the same to have it borematched?

sooo now i need to get me some rifling :bang:

timefreak17 02-01-2013 02:52 AM

It would be interesting to see a barrel made to line up with the first strike rifle grooving. I would say that with a rifled barrel it is possible that the FS rounds would catch the rifling and start the rotation in the barrel if the barrel was sized correctly.

I don't know too much nor have i tested out FS rounds with a hammerhead barrel or the like.

I feel that the fs round would have to be chambered to line up with the grooving of a rifled barrel in order to create the best rotation and accuracy. Yet right now I don't see any manufactures creating FS round specific rifled chambers and barrels that allow for the perfect "cambering" of the FS round.

Correct me if i'm wrong....just what i'm thinking or seeing

Grelvire 02-01-2013 09:16 AM

I would think that unless the rifling's twist matched the rotations per second of the first strike being shot all this would serve to do is disrupt the first strike rounds trajectory causing less accurate shots

uv_halo 02-01-2013 10:02 AM

Quote:

Originally Posted by tymcneer (Post 2610853)
I wish to start a discussion regarding First Strike and rifling....

...Taking these two pieces of information into account, I would suggest that rifling will improve both accuracy, by reduction of the initial wobble, before the round spins up, and range, by not using up kinetic energy, converting it into rotational energy.

Thoughts on:
- Twist rate
- Style of rifling
- Anything else that seems relevant to the conversation.

Ty

I suspect that they could benefit from rifling.

Here's what I know:
  • The I.D. of the rifled barrel is .683
  • The twist rate of the fins do not match the twist rate of the LAPCO/Tiberius barrel.
  • The fins are narrower than the waist / equator of the round.
  • I successfully recovered intact rounds fired through the rifled barrel and there was no evidence of any scoring or scratching on the rounds, at all.
  • I have seen High Speed Video from an independent source that shows the LAPCO/Tiberius barrel (I assume the full length version) actually imparting a spin on the rounds.
  • The LAPCO/Tiberius barrel experiences heavy fouling and requires cleaning after around 80-100 rounds to prevent a round seizing halfway down the barrel.

What I don't know:
  • Does the spin imparted by the LAPCO/Tiberius barrel actually improve the performance (range or accuracy) of the rounds?
  • Is there a difference in performance between the short and long LAPCO/Tiberius barrels?
  • Does a looser rifling design (i.e. Hammerhead) apply spin?
  • Does a looser rifling design improve performance (range or accuracy)?

What I'm hoping for:
A dual chronograph test to see if there is a reduction in drag by pre-spinning them.
Accuracy testing on the LAPCO/Tiberius and Hammerhead barrels.

Quote:

Originally Posted by Brassballs (Post 2610871)
The fins on the FSR function the same as fletching on an arrow.
I'd think a rifled barrel would do little to nothing(at best) to improve the flight and distance plus it could possibly damage them.

By pre-spinning the rounds you might reduce the drag required to get them up to the proper RPM. This could effectively improve range. The rounds may also stabilize in flight a bit sooner allowing for an increase in accuracy. Punkworks is currently preparing to test at least

Here's the catch- the skirt is actually narrower than the equator/waist of the round and, it least in the LAPCO/Tiberius design, it's at a different twist rate than the skirt.

Quote:

Originally Posted by Cheeserocket (Post 2610873)
The video doesnt say what kind of bore it was, would a .695 id make it spin before it leaves the barrel? or would it be the same to have it borematched?

sooo now i need to get me some rifling :bang:

I suspect it's a .689 boomstick but, I'd need Bryce or Cockerpunk to confirm.

timefreak17 02-01-2013 10:15 AM

I have a hammerhead barrel with fins for a phantom that I am willing to lend out if some one wants to do the testing with it. Or just the barrel if others have fins.

Also another thing to consider... would sizing FS rounds to a detente such as tymcneer brass inserts help the FS round with stabilization in the barrel; being that the skirt is narrower than the diameter of the paintball?

Also would having a detente also cause the skirt to splay out and catch the grooving of a rifled barrel? Or is the skirt to rigid for that?

tymcneer 02-01-2013 03:15 PM

Some more factors to consider...

- Friction melting of the polystyrene shells, assuming the barrel were tight enough, and the velocity sufficent to produce that level of heat

- The shape and quantity of the lands and grooves in order to get a better grip on the round, and help to eliminate fouling, by reducing the shear forces the round experiences during spin up.

UV_Halo - I happen to have a 150 foot outdoor range and quite a few optical chronographs. Want to have some fun and collect some data?

You bring the marker and we can split the cost on the FSR... I will bring the measuring devices :)

The next major investment is likely to be a CNC rifling machine, so I can build test barrels.


Ty

uv_halo 02-01-2013 03:38 PM

Well, when it comes to accuracy, I rely on indoor testing in order to better separate the 'signal' (improvement in accuracy) from the 'noise' (0-3mph drafts that we cannot necessarily feel but, will drift rounds).

Dual Chrono tests can be done outdoors with the optical chronos, as long as we can reliably determine that we've got a crosswind vs a tail or headwind.

Bryce and Cockerpunk will be testing one or both of these aspects soon. So, if they knockout accuracy, I would help with the dual chrono test if it was needed.

dano_____ 02-01-2013 04:39 PM

So here is a random question regarding a rifled barrel and related to fs rounds. Could a smooth fs round be developed(no fins) that actually engages rifling and could have the spin imparted on it? Better yet use the hydrotec fill, even if we never actually see it in a normal paintball, to eliminate the fluid rotation that can occur with standard fill. Sorry if it is a bit askew from the original post, just a thought.


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