General

[drg]

I am fairly sure shorter backs or step bores are more tolerant of underbore. I seem to regularly get paint up to and over .690, so for people like me, many modern underbore barrels are not the best.

EDIT: y'know, I wonder if it 's possible to get different results depending on not just the underbore but the absolute size of the ball. For example a .015 underbore at .695 may react differently than .015 underbore at .680. The forces are not the same (e.g. as far as deforming the gelatin vs breaking it) no?

[PistolRogue]

I believe that a .680 ball (assuming the same exact shell thickness) would be much stronger than a .690 ball, at least in terms of scale and crushing force. I could be wrong though, definitely not one of the resident math/engineering geeks.

[drg]

Or would the 690 ball tolerate more flex?

[brycelarson]

when we did the compression test we found that most paint could flex somewhere in the neighborhood of .125" before it gave out. Obviously we're not talking anything like that sort of deformation in a barrel.

My guess, based on looking at underbores small enough that they cause breaks - is that the breaks are mostly seam failures. This may mean that the amount you can underbore is more related to the seam orientation than the total underbore level.

[Looper]

I under stand the concept of less drag equal greater efficiency that is being sold on the TechT site but what about my trusty Automag that if "dry fired" will drain an hpa tank in no time.

I would be interested in seeing what effects the drag has on the efficiency of the Automag blow forward system where the valves dwell is controlled by the bolt return spring. Is more control bore length better for the Automag?

[drg]

Originally Posted by brycelarson

My guess, based on looking at underbores small enough that they cause breaks - is that the breaks are mostly seam failures. This may mean that the amount you can underbore is more related to the seam orientation than the total underbore level.

... or seam strength. Some balls break along the seams, others don't

Can you link me to the "compression test" again?

[Poe]

Originally Posted by Looper

I under stand the concept of less drag equal greater efficiency that is being sold on the TechT site but what about my trusty Automag that if "dry fired" will drain an hpa tank in no time.

I would be interested in seeing what effects the drag has on the efficiency of the Automag blow forward system where the valves dwell is controlled by the bolt return spring. Is more control bore length better for the Automag?

I think the concept is "better seal better efficiency". After reading nearly every post in the Deepblue forums it's my understanding the Automag's dwell is mostly dependent on back-pressure and is consistent because of it. A lousy ball seal equates to less back-pressure which equates to longer dwell and therefore less efficiency. No ball is the extreme case. I never liked the idea of using it in the Punkwork's tests because of that very reason.

[Shawn_Savage]

Originally Posted by drg

... or seam strength. Some balls break along the seams, others don't

I think this would play a huge factor.

At my field we have a bunch of Diablo Heat. Normally it's crappy paint but this stuff has extraordinarily weak seams. You can drop it from your waist and if it hits along the seam line then the ball will break clean in half. If comparing the seam breaks to my overall ultra evil brittleness then this heat is easily more brittle.

Good for me but it sucks because that's what we put through our BT rentals. Shoots fine unless it catches the seam right and splits the ball in half.

[Mann]

Kinda late to the game, but.......

Would this not be the same theory that ccm/stiffi/sly/otp did? otp's barrel theory was almost identical, but was only ~1" long. and ccm/stifi/sly all said you only needed 2" of control bore.

Does this barrel provide something that is not out there already? (other than the smaller sizes which imo is something that more should do.)

/not trying to put down any barrel/barrel mfrg. just wondering.

[brycelarson]

Originally Posted by drg

Can you link me to the "compression test" again?

most of our tests are here:
PunkWorks Paintball - The Science Side of Paintball -

compression test is here:
PunkWorks Paintball - The Science Side of Paintball -

we're working on a search feature.

Originally Posted by Poe

No ball is the extreme case. I never liked the idea of using it in the Punkwork's tests because of that very reason.

yeah, there should be a curve of some sort in there from large underbore to dry fire - but we were asked specifically about dry firing vs shooting paint. so we tested that.