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Control Bore Length or Bore Size


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#1 unfated33

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Posted 13 January 2013 - 09:25 PM

More and more I've been seeing recommendations in the equipment advice section that people buy insert-style marker barrels because the player can then optimize their paint bore to the paint they are playing with. It appears the message of using a slight underbore has come in loud and clear to the player base. However, by recommending the insert-style barrels it would appear that the forum is taking the stance that bore size is more important to marker efficiency than the control bore length. What I'm curious to know is whether that's really the case?

Looking at the most recent data that Gordon and Bryce took from their Bore Accuracy Test, it would appear that a slightly overbored one-piece CP barrel provided a higher velocity average than any of the freak inserts, even those that were as much as .008 underbored. This would imply that control bore length is a more important variable in efficiency than the bore size. Is this result statistically significant? Is there any more data out there to compare velocity and consistency between insert-style barrels and barrels with an 8-10" control bore? I thought that Lurker had a comparison of a lot of different barrels on their website, but it appears that it's been removed - and even then, I don't know if it compared insert-style barrels in their chart.

If the Bore Accuracy Test data shows that control bore length is more important than bore size, I think that's a message that really needs to be reinforced in the TechPB community. Especially when considering the price paid for the insert kits like the Empire Freak, GOG Freak, and DeadlyWind Fibur compared to a CP or Lurker barrel.
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#2 andrewthewookie

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Posted 13 January 2013 - 09:50 PM

Looking at that data, I do not see if it says if the gun was re-chrono'd in between barrels. Before we can make conclusions about bore size and velocity, we need to know that.

I personally prefer insert style barrels because of the versatility they allow.

Edited by andrewthewookie, 13 January 2013 - 10:32 PM.

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#3 tallsmallboy44

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Posted 13 January 2013 - 10:31 PM

I think that the Insert style underbore idea has been suggested as it has, because it has been proven that an underbore provides an increase in efficiency, where as I have yet to see any tests done on the bore length theory. I also don't think it would hurt to have a barrel that could combine both, a long control bore as well as the insert style barrel.

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#4 unfated33

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Posted 14 January 2013 - 06:33 AM

I think that the Insert style underbore idea has been suggested as it has, because it has been proven that an underbore provides an increase in efficiency, where as I have yet to see any tests done on the bore length theory. I also don't think it would hurt to have a barrel that could combine both, a long control bore as well as the insert style barrel.

You may find this post by Cookybiscuit in the Punkworks forum may bring you up to speed. At the very least, there have been tests done on bore length by Flasc, Punkworks, and rntlee.
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#5 unfated33

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Posted 14 January 2013 - 08:31 AM

Looking at that data, I do not see if it says if the gun was re-chrono'd in between barrels. Before we can make conclusions about bore size and velocity, we need to know that.

Good point - I think there's more than a chance it was re-chrono'd each time. In which case, there might be no data to indicate whether optimal underbore or optimal control bore length contribute more to efficiency. Which means, hooray - testing opportunities!
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#6 brycelarson

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Posted 14 January 2013 - 09:14 AM

In accuracy tests we re-chrono between systems. Unless the test specifically indicates that we did not - then no efficiency determinations should be made from those tests.

Here's our control bore length test:

http://www.punkworks...x.php?p=7&id=42

#7 unfated33

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Posted 14 January 2013 - 11:27 AM

In accuracy tests we re-chrono between systems. Unless the test specifically indicates that we did not - then no efficiency determinations should be made from those tests.

Here's our control bore length test:

http://www.punkworks...x.php?p=7&id=42

I'm not sure I'm seeing what I'm looking for in the test you did, though. I apologize if this seems like a wall of questions.

In an insert-style barrel, does the control bore constitute the entire non-ported length or only the length up to the end of the insert when the barrel ID increases?
Shouldn't the velocity of the paintball begin to slow when moving from a narrower ID to a wider ID, or will only the propellant air itself slow at the diameter change?
Am I correct in understanding that you re-chrono between using the 0.682 bore, 0.688 bore, and 0.693 bore back for each of the unported lengths in the test you linked to?
For each of the Flasc backs, am I discerning correctly that the control bore length is 8.5-inches (2.5 flasc shot), 11 in. (5 flasc shot) 13 in. (7 flasc shot), 12 in. (9 flasc shot), 11 in. (11 flasc shot)? Did none of the test cases look at a 5 in. control bore length?
Have there been comparisons of control bore length in an underbore situation, and/or does the data extrapolate linearly from overbore to underbore?
Can we draw reasonable conclusions of the insert-style barrels from the 2.5 inch flasc back since there's very little data on the 5-inch back?
Is the data here in your test and I'm missing it whether bore length or bore size is a greater contributor to efficiency? Is this a question that has an answer well established?
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#8 brycelarson

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Posted 14 January 2013 - 12:36 PM

Cool, lots of questions - answers in red

I'm not sure I'm seeing what I'm looking for in the test you did, though. I apologize if this seems like a wall of questions.

In an insert-style barrel, does the control bore constitute the entire non-ported length or only the length up to the end of the insert when the barrel ID increases?

We normally consider it the control bore until either porting starts OR the bore size steps up significantly. It's a bit vague due to the large variation in barrel designs.

Shouldn't the velocity of the paintball begin to slow when moving from a narrower ID to a wider ID, or will only the propellant air itself slow at the diameter change?

Neither - the ball continues to accelerate past the control bore section. https://spreadsheets...HdSUAE5ioZ_zbNA

Am I correct in understanding that you re-chrono between using the 0.682 bore, 0.688 bore, and 0.693 bore back for each of the unported lengths in the test you linked to?

Yes. Inside sets we do no chrono - when starting a new set we do.

For each of the Flasc backs, am I discerning correctly that the control bore length is 8.5-inches (2.5 flasc shot), 11 in. (5 flasc shot) 13 in. (7 flasc shot), 12 in. (9 flasc shot), 11 in. (11 flasc shot)? Did none of the test cases look at a 5 in. control bore length?

It's a tough test to describe due to the massive variables in the FLASC gear. Basically we used multiple tips to try to keep each barrel as close to 14" long total as possible. See the notes at the top left of the document. For example, when shooting the 5" back we used a 6" unported section (bore .700) and a 3" ported section (bore .700) for a total barrel length of 14" with three ported. On the 9" back we used a 3" unported tip and a 3" ported tip for a total barrel length of 15" with 3" ported. The bore lengths we shot for each set was 2.5, 5, 7, 9, 11".

Have there been comparisons of control bore length in an underbore situation, and/or does the data extrapolate linearly from overbore to underbore?

Due to paint and equipment we were able only to do paint match and overbore for this test. Based on all of our other testing it's reasonable to extrapolate an across the board increase in velocity in a linear relationship when moving to underbore.

Can we draw reasonable conclusions of the insert-style barrels from the 2.5 inch flasc back since there's very little data on the 5-inch back?

See above. And in general we find that manufacturer, design etc has very little to do with performance. A given bore and length of barrel of any design tends to produce similar results.

Is the data here in your test and I'm missing it whether bore length or bore size is a greater contributor to efficiency? Is this a question that has an answer well established?

Take a look at the bottom left section of the data. That's various bore sizes of the 9" back with a single 3" ported tip. 12" total length, 9" of control bore and the variable is the bore size. Highest velocity to lowest velocity is a 50 fps swing. Looking at the top left data set the swing from shortest control bore to longest bore with the overall barrel length staying the same the highest velocity to lowest is statistically insignificant. Here's another test: https://spreadsheets...HdSUAE5ioZ_zbNA
This one shows that there's a slight increase in efficiency when moving from 10" up to about 14 or 16" and then a decrease past that.


So, based on our conglomerated testing: #1 efficiency gain - bore size, #2 barrel length, #3 control bore length.

#9 unfated33

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Posted 14 January 2013 - 04:36 PM

Cool, lots of questions - answers in red
So, based on our conglomerated testing: #1 efficiency gain - bore size, #2 barrel length, #3 control bore length.

Awesome response, thanks!
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#10 brycelarson

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Posted 15 January 2013 - 06:47 AM

optimal for each:

bore - .003-.005 underbore
length - 14-16"
control bore length - about 9-11" depending on gun

Edited by brycelarson, 15 January 2013 - 09:20 AM.


#11 Troy

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Posted 15 January 2013 - 06:17 PM

optimal for each:

bore - .003-.005 underbore
length - 14-16"
control bore length - about 9-11" depending on gun


Maybe this is a silly question, maybe not. How do you measure the bore size of a ball with just inserts (or barrels) that you have on hand? If we are supposed to use calipers... that's a little hard to do on the field (assuming you don't take a pair of calipers with you... which I may end up having to do).

I guess the answer would be that I would have to just practice a bit with some inserts and paintballs and a pair of calipers... but I wouldn't mind some ideas that are more repeatable.
\m/

#12 brycelarson

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Posted 16 January 2013 - 09:19 AM

Maybe this is a silly question, maybe not. How do you measure the bore size of a ball with just inserts (or barrels) that you have on hand? If we are supposed to use calipers... that's a little hard to do on the field (assuming you don't take a pair of calipers with you... which I may end up having to do).

I guess the answer would be that I would have to just practice a bit with some inserts and paintballs and a pair of calipers... but I wouldn't mind some ideas that are more repeatable.


Reality for me is that I toss a .687 Lurker, a .685 Lurker and a .689 Stiffi in my gear bag and go play. I start with the .687 - if things are wonky I move up a barrel.

When I have a freak kit on site I use my inserts and do the blow test - them move down one or two. I want to have to push the ball though with my swab. That's about .004-5 under. I culled my inserts so that while not all of them are exactly the same size as they're marked - they are all in order (ie the .685 may be .686 but it's still smaller than the .687 and bigger than the .683).

#13 Troy

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Posted 16 January 2013 - 09:29 AM


Maybe this is a silly question, maybe not. How do you measure the bore size of a ball with just inserts (or barrels) that you have on hand? If we are supposed to use calipers... that's a little hard to do on the field (assuming you don't take a pair of calipers with you... which I may end up having to do).

I guess the answer would be that I would have to just practice a bit with some inserts and paintballs and a pair of calipers... but I wouldn't mind some ideas that are more repeatable.


Reality for me is that I toss a .687 Lurker, a .685 Lurker and a .689 Stiffi in my gear bag and go play. I start with the .687 - if things are wonky I move up a barrel.

When I have a freak kit on site I use my inserts and do the blow test - them move down one or two. I want to have to push the ball though with my swab. That's about .004-5 under. I culled my inserts so that while not all of them are exactly the same size as they're marked - they are all in order (ie the .685 may be .686 but it's still smaller than the .687 and bigger than the .683).


Sounds good... you probably meant to say .678 instead of .687 though :rolleyes:
\m/

#14 brycelarson

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Posted 16 January 2013 - 11:00 AM

Sounds good... you probably meant to say .678 instead of .687 though :rolleyes:


correct

#15 JasonSaastad

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Posted 18 January 2013 - 12:37 AM

optimal for each:

bore - .003-.005 underbore
length - 14-16"
control bore length - about 9-11" depending on gun


Does a lack of porting for those last few inches have a negative impact on consistency or accuracy?

I'm looking at purchasing a two custom single piece 14" barrels with .682 and .685 bores without porting to go along with my .679.

#16 brycelarson

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Posted 18 January 2013 - 04:17 PM


optimal for each:

bore - .003-.005 underbore
length - 14-16"
control bore length - about 9-11" depending on gun


Does a lack of porting for those last few inches have a negative impact on consistency or accuracy?

I'm looking at purchasing a two custom single piece 14" barrels with .682 and .685 bores without porting to go along with my .679.


the porting actually seems to increase consistency somewhat - and does not decrease efficiency. I only shoot ported barrels.

#17 ScaryfatkidGT

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Posted 13 February 2013 - 04:58 AM

I've been wondering this same thing, is a freak kit any better or worse than a CP or Dye UL 2 piece kit?

The thing is CP only makes .693 .689 and .685 when I think .691 and .687 are really useful

And CP one piece barrels are the price of the barrel backs so you could just have a bunch of barrels and have an even longer control bore.




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