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Punkworks posters - a call to test


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#1 Snipez4664

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Posted 09 April 2012 - 12:32 AM

Punkworks,

I reproduced the Tom Kaye "powder" test in an overbored 2 piece today, with some interesting results. We'll get to that later, but it was such a fast and easy test, I was hoping we could all grab some data - I'll check eigenbarrels next week, I just shot a dye UL real quick because I was looking specifically at the overbored tip. I used standard baby powder, worked great.


Anyway, if anyone wants to do the test, here are some interesting things to look at:

1. What gun, paint and barrel setup?

2. Bounces or skips - will the side to side motion of the ball always alternate, or will air pressure make the ball hit the same side twice in a row (or both, randomly)

3. Was the bounce pattern repeatable in your gun (location of impact spots)

4. Where were the bounces?




My answers:

1. Empire AXE, Lurker bolt, ~.686 paint, .689 Dye UL w/ .700 tip

2. Bounces (alternating sides)

3. Yes, it seemed to be concentrated in one orientation and didn't even out until i messed around with partially unscrewing the barrel to get different positions.

4. I didn't take good enough notes on this because I'm a chobo but I believe it was up/down orientation, with lots of bounces near the back, and much fewer as we move towards the tip. still, looked like maybe 30% of shots contacted inside the tip to at least some degree.

Edited by Snipez4664, 09 April 2012 - 09:48 AM.

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#2 cockerpunk

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Posted 09 April 2012 - 08:53 AM

we should keep track of what gun you use as well.
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And yes, Gordon is the sexiest manifestation of "to the front."


#3 Troy

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Posted 09 April 2012 - 09:20 AM

we should keep track of what gun you use as well.


And any bolt modifications... since Jack Wood seemed to imply that bolts had some effect.

Edited by Troy, 09 April 2012 - 09:21 AM.

\m/

#4 cockerpunk

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Posted 09 April 2012 - 09:24 AM

i think the CFD analysis i did back in college points pretty well to bolt/valve air flow pattern effects.

its hard, but its worth trying to take down barrel pictures, use a white sheet of paper or something to get nice internal reflection.
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#5 Snipez4664

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Posted 09 April 2012 - 09:48 AM

First post edited
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#6 Troy

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Posted 09 April 2012 - 10:15 AM

i think the CFD analysis i did back in college points pretty well to bolt/valve air flow pattern effects.


Would you mind expanding upon this, and underlining it's relevance to this discussion? I don't want to just ASSUME I know what you are talking about.
\m/

#7 cockerpunk

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Posted 09 April 2012 - 10:31 AM


i think the CFD analysis i did back in college points pretty well to bolt/valve air flow pattern effects.


Would you mind expanding upon this, and underlining it's relevance to this discussion? I don't want to just ASSUME I know what you are talking about.


i did some CFD work on flow through a stacked tube poppet. it showed that before the ball accelerates, the air already in the bolt/valve when the power pulse comes through, tends to "pool" at the top of the bolt, and the power pulse tends to stay low, and pushes under it. the force on the paintball pre-motion is heavily unbalanced towards the base of the bolt.
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#8 Troy

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Posted 09 April 2012 - 02:44 PM



i think the CFD analysis i did back in college points pretty well to bolt/valve air flow pattern effects.


Would you mind expanding upon this, and underlining it's relevance to this discussion? I don't want to just ASSUME I know what you are talking about.


i did some CFD work on flow through a stacked tube poppet. it showed that before the ball accelerates, the air already in the bolt/valve when the power pulse comes through, tends to "pool" at the top of the bolt, and the power pulse tends to stay low, and pushes under it. the force on the paintball pre-motion is heavily unbalanced towards the base of the bolt.


If that is the case, then it would also be a good idea to mark the vertical axis on any barrel pictures that are made as well.
\m/

#9 drg

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Posted 09 April 2012 - 04:24 PM

Can you describe the process of applying the baby powder?
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#10 Snipez4664

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Posted 09 April 2012 - 09:59 PM

I just liberraly poured into the barrel and shot once, with paint - it evenly distributed after a single shot and i didn't have to reapply (though i was overbored, but that's sort of the point since we know what is going on with 1 piece underbores
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#11 drg

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Posted 09 April 2012 - 10:45 PM

Which end did you pour it in? was the ball loaded?
Sorry I just have never done it and want to get it right and consistent with yours.
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#12 Snipez4664

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Posted 09 April 2012 - 11:59 PM

i left my loader on the whole time, so yea a ball was loaded

i unscrewed the barrel, poured in the breech end, rescrewed the barrel, shot once, and checked. Was happy with distribution so i went from there
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#13 drg

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Posted 10 April 2012 - 01:42 AM

i left my loader on the whole time, so yea a ball was loaded

i unscrewed the barrel, poured in the breech end, rescrewed the barrel, shot once, and checked. Was happy with distribution so i went from there


was the ball in the breech or the barrel? i.e. was the powder in front or behind the ball?
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#14 Snipez4664

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Posted 10 April 2012 - 02:29 AM

barrel was empty; poured powder into the barrel mouth
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#15 drg

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Posted 10 April 2012 - 03:01 AM

barrel was empty; poured powder into the barrel mouth


Ok got it, earlier when you said this:

I just liberraly poured into the barrel and shot once, with paint - it evenly distributed after a single shot and i didn't have to reapply (though i was overbored, but that's sort of the point since we know what is going on with 1 piece underbores



it sounded like you had a paintball loaded when you put the powder in.
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#16 Snipez4664

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Posted 14 April 2012 - 01:18 PM

bump cmon guysI'm trying to figure some stuff out

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Edited by Snipez4664, 14 April 2012 - 01:19 PM.

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#17 drg

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Posted 14 April 2012 - 02:01 PM

You're modeling alka seltzer? :D
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#18 brycelarson

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Posted 14 April 2012 - 02:25 PM

what is that snipes?

#19 H all day

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Posted 14 April 2012 - 02:32 PM

what is that snipes?

its the flight paths of paintballs i think
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#20 cockerpunk

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Posted 14 April 2012 - 04:11 PM

CFD of a barrel ^^^^^

not sure how relivent it is right now though, without the back pressure of the ball (which is hard as hell to model), not sure how much it tells us.
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#21 drg

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Posted 14 April 2012 - 07:27 PM

Well I tried the experiment today and failed. Maybe it's because I used the cornstarch type? Anyway firing the ball just blew out all the powder and I could not see any pattern. It was a Lapco barrel though so maybe the finish sloughed off all the powder.
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#22 Snipez4664

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Posted 15 April 2012 - 01:13 PM

Not sure, but thats for trying

Gordon I don't think it tells us anything either but I wanted attention
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#23 brycelarson

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Posted 15 April 2012 - 05:19 PM

Well I tried the experiment today and failed. Maybe it's because I used the cornstarch type? Anyway firing the ball just blew out all the powder and I could not see any pattern. It was a Lapco barrel though so maybe the finish sloughed off all the powder.


I've done it with flour in the past. Most of the powder leaves - yes, but you'll end up with slightly more clean portions where the ball landed.

#24 drg

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Posted 15 April 2012 - 11:39 PM

There was no discernible powder in the barrel after the shot...
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#25 Jack Wood

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Posted 16 April 2012 - 12:02 PM

Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

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#26 cockerpunk

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Posted 16 April 2012 - 12:31 PM

Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

Jack


its got to be either differential in power pulse pressure, or non centering of the ball in the breach/loading.

or both?

loading/non centering would probably lead to even spool valves doing it, which i dont think is the case.

means its got to be a differential in power pulse pressure.

Edited by cockerpunk, 16 April 2012 - 12:32 PM.

The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#27 Troy

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Posted 16 April 2012 - 12:58 PM

I was thinking about, possibly, using a towel to build up an electrostatic charge as well.

Btw, do we know if the vertical orientation of the marker effects it or not? If it does effect it, it would lend confirmation to a non centering loading problem like CP said, if it doesn't effect it, it would be pretty strong evidence that it is probably an air flow related issue.

I think it would be interesting to see if a marker's detents effect the barrel bounce also.

Edited by Troy, 16 April 2012 - 01:48 PM.

\m/

#28 mr.satire

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Posted 16 April 2012 - 08:22 PM


Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

Jack


its got to be either differential in power pulse pressure, or non centering of the ball in the breach/loading.

or both?

loading/non centering would probably lead to even spool valves doing it, which i dont think is the case.

means its got to be a differential in power pulse pressure.


Gordon when you did your CFD modeling of the bolt system, did you include a "venturi" face or was it just an open bolt? Im wondering if that could affect the way the power pulse flows

#29 cockerpunk

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Posted 16 April 2012 - 09:06 PM



Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

Jack


its got to be either differential in power pulse pressure, or non centering of the ball in the breach/loading.

or both?

loading/non centering would probably lead to even spool valves doing it, which i dont think is the case.

means its got to be a differential in power pulse pressure.


Gordon when you did your CFD modeling of the bolt system, did you include a "venturi" face or was it just an open bolt? Im wondering if that could affect the way the power pulse flows


IIRC i did. i should look that up, its got to be in the experiment vault somewhere.
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And yes, Gordon is the sexiest manifestation of "to the front."


#30 Jack Wood

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Posted 17 April 2012 - 04:37 AM


Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

Jack


its got to be either differential in power pulse pressure, or non centering of the ball in the breach/loading.

or both?

loading/non centering would probably lead to even spool valves doing it, which i dont think is the case.

means its got to be a differential in power pulse pressure.


Remember when I showed you the very first HSV footage all those years ago? Remember the "negative" kick we saw? Well a cup faced bolt that is pushing a ball into the barrel on a poppet gun undergoes the same phenomena. Where does a bolt pivot around when the rammer strikes the poppet valve? What would the resultant be when that happens?

It's easy to assume that the bolt has only one degree of freedom as it cycles, but that would be incorrect.
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#31 mr.satire

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Posted 17 April 2012 - 10:35 PM



Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

Jack


its got to be either differential in power pulse pressure, or non centering of the ball in the breach/loading.

or both?

loading/non centering would probably lead to even spool valves doing it, which i dont think is the case.

means its got to be a differential in power pulse pressure.


Remember when I showed you the very first HSV footage all those years ago? Remember the "negative" kick we saw? Well a cup faced bolt that is pushing a ball into the barrel on a poppet gun undergoes the same phenomena. Where does a bolt pivot around when the rammer strikes the poppet valve? What would the resultant be when that happens?

It's easy to assume that the bolt has only one degree of freedom as it cycles, but that would be incorrect.


The pivot would be at the point where the valve stem, contacts the rammer. The result would be a force on the bolt that would cause the tip to dip downwards slightly.


I really cant think of any other way to word it wich is sad considering im an ME student

#32 rntlee

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Posted 18 April 2012 - 05:49 AM

That's interesting, but wouldn't TK have been testing with Mags?

#33 Troy

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Posted 18 April 2012 - 07:06 AM

The pivot would be at the point where the valve stem, contacts the rammer. The result would be a force on the bolt that would cause the tip to dip downwards slightly.


I really cant think of any other way to word it wich is sad considering im an ME student


I'm pretty sure Jack knows where the pivot is, and was just asking the question as a rhetorical device. :D

I'm going to test my AKA (as soon as it gets back from destructive customs) verses my only spool, a PM6. It's pretty conventional wisdom that AKA's were built with really high tolerances, and I'm wondering if that would effect how much (I'm going to coin a new phrase here) bolt dive it would have. Furthermore, because the hammer is off center, it would probably make a different looking pattern in the barrel.
\m/

#34 Jack Wood

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Posted 18 April 2012 - 08:09 AM

That's interesting, but wouldn't TK have been testing with Mags?


And where did Tom say he saw the bounces?
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#35 Troy

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Posted 18 April 2012 - 08:29 AM

I'm going to hurt someone if we don't get a nelson based marker tested.
\m/

#36 cockerpunk

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Posted 18 April 2012 - 08:45 AM



Humidity or condensation may play a part in how well the powder adheres to the inside of the barrel. How about breathing through the barrel first and then pouring the powder through?

Regarding bounce initiation, we can see it clearly when using a poppet based gun. I haven't revealed the cause of the initial instability so far. I was hoping someone would try and work it out :)

Jack


its got to be either differential in power pulse pressure, or non centering of the ball in the breach/loading.

or both?

loading/non centering would probably lead to even spool valves doing it, which i dont think is the case.

means its got to be a differential in power pulse pressure.


Remember when I showed you the very first HSV footage all those years ago? Remember the "negative" kick we saw? Well a cup faced bolt that is pushing a ball into the barrel on a poppet gun undergoes the same phenomena. Where does a bolt pivot around when the rammer strikes the poppet valve? What would the resultant be when that happens?

It's easy to assume that the bolt has only one degree of freedom as it cycles, but that would be incorrect.


ah, you are implying that the bolt itself rotates about the hammer/valve stem point which directs air at an angle .... mmmmm. so can you possible manipulate that with the fit and length of the bolt? that would be the test there.

so why then would we see bouncing on a gun like the AXE that lurker sees? that screams airflow to me, that the AXE volume near the poppet isn't enough, and it taps into the gas transfer tube in the frame, which gives it a pressure differential across the bolt face, and thus a bounce.
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#37 Troy

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Posted 18 April 2012 - 09:11 AM

so why then would we see bouncing on a gun like the AXE that lurker sees? that screams airflow to me, that the AXE volume near the poppet isn't enough, and it taps into the gas transfer tube in the frame, which gives it a pressure differential across the bolt face, and thus a bounce.


Could we test a bolt with an open face verses something like a cooper t bolt or alien sweep bolt and see if there are any differences?
\m/

#38 Snipez4664

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Posted 18 April 2012 - 01:09 PM

I don't know no one seems very interested in actually testing this

don't you guys own paintball guns?

we're trying to build a data set here
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#39 y0da900

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Posted 18 April 2012 - 09:27 PM

It's the baby powder that's stopping me. I'll try and remember to get some on the way home from work tomorrow. I'll run a test with 4 or 5 guns - both open and closed bolt of both poppets and spools. Removing the moment caused from the eccentrically loaded moving bolt during the poppet impact using a closed bolt poppet should be a pretty good indicator whether or not that or the airflow is the cause - also removes detents from the equation, which is easy enough to double check by single loading balls into an open bolt with detents removed.

#40 Troy

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Posted 18 April 2012 - 10:01 PM

My primary is in the shop, and the noid on my only backup just went bad... anyone know where you can get a noid for a PM6 ?:angry:

Anyways, some alternative materials that I thought of, because like y0da900 I don't have baby powder:
1) flour
2) Bisquick
3) vegetable oil or nonstick cooking spray (especially if you can spray it down the barrel)
\m/

#41 cockerpunk

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Posted 18 April 2012 - 10:14 PM

It's the baby powder that's stopping me. I'll try and remember to get some on the way home from work tomorrow. I'll run a test with 4 or 5 guns - both open and closed bolt of both poppets and spools. Removing the moment caused from the eccentrically loaded moving bolt during the poppet impact using a closed bolt poppet should be a pretty good indicator whether or not that or the airflow is the cause - also removes detents from the equation, which is easy enough to double check by single loading balls into an open bolt with detents removed.


if you could try 1 pc vs 2 pc too. interested in what happens in the tip of the barrel.
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#42 Jack Wood

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Posted 19 April 2012 - 05:32 AM

ah, you are implying that the bolt itself rotates about the hammer/valve stem point which directs air at an angle .... mmmmm. so can you possible manipulate that with the fit and length of the bolt? that would be the test there.

so why then would we see bouncing on a gun like the AXE that lurker sees? that screams airflow to me, that the AXE volume near the poppet isn't enough, and it taps into the gas transfer tube in the frame, which gives it a pressure differential across the bolt face, and thus a bounce.


Actually the cup in the face of the boltdipping down pushes the ball to the bottom of the barrel prior to the pulse hitting the ball. The gas then exploits this positioning of the ball.

As to why you would see it in the Axe, well maybe the spring is causing a tipping actionas it compresses?

The detents don't have any effect on the ball being loaded into the barrel. Certainly our rubber finger detents do nothing at all compared to the loading and firing forces involved.
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#43 y0da900

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Posted 19 April 2012 - 08:47 PM

Didn't get to do a whole lot of testing tonight, but so far I have gotten no consistent bounce or rub marks shot to shot in the back or tip when using a mechanical Matrix. I was shooting paint (and reballs) through a pipe kit - both the .683 back (which is closer to .681) and the .695 (which I have never checked with my bore gauge). Like others, I'm having difficulty getting a good coating of baby powder to stay reliably. I tried breathing through the barrel, putting some light air tool oil on a paper towel to swab it, and dry. I think next time I get a chance to try it, I will try a light misting of silicone lubricant spray.

#44 rntlee

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Posted 19 April 2012 - 09:28 PM

Just a question...at what point in trying to obtain a measurement does this method of testing become obtrusive to the proper action of the marker/barrel?




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