[Iram]

How long are the CP backs?

So, looking at the results, I (who suck at statistics) would conclude:

1. Tighter bore = higher velocities.

2. For one-piece barrels, 14" is the ideal length.

3. For two-piece barrels, the length of the tip matters a little, but anything from 10-16" is going to perform about the same. Yeah, they varied, but the differences were all pretty much within the standard deviation. With things that close, personal preference (ergonomics) is probably more important when actually playing paintball.

Any ETA for the results of your accuracy tests? I'm planning to buy a new barrel based on the final results of these tests, and I was hoping to have that show up on my December budget instead of January.

EDIT: Bryce, I just saw your response about the sorting. That makes a lot of sense.

This post has been edited by Iram: 29 December 2008 - 05:03 PM

[Poe]

brycelarson, on Dec 29 2008, 03:55 PM, said:

automag shoot-up.

Since these tests are using velocity change as the measured variable, shouldn't a marker that doesn't have velocity issues be used? Maybe an Ion with max dwell?

I'm assuming the main point of the barrel length tests was to determine if barrel length effected consistency? Each marker has a barrel length that is most efficient for its setup. Might want to put a disclaimer here so no one thinks a 14" barrel is most efficient on their gun... unless they have the same exact Emag setup.

Did all barrels have the same exact porting? What was the distance from the barrel tip to the start of the porting?

Was paint to barrel match .683?

Adjusting for the mag's shoot-up, it looks like length had a negligible effect on velocity consistency.

[brycelarson]

Poe, on Dec 29 2008, 04:06 PM, said:

brycelarson, on Dec 29 2008, 03:55 PM, said:

automag shoot-up.

Since these tests are using velocity change as the measured variable, shouldn't a marker that doesn't have velocity issues be used? Maybe an Ion with max dwell?

I'm assuming the main point of the barrel length tests was to determine if barrel length effected consistency? Each marker has a barrel length that is most efficient for its setup. Might want to put a disclaimer here so no one thinks a 14" barrel is most efficient on their gun... unless they have the same exact Emag setup.

Did all barrels have the same exact porting? What was the distance from the barrel tip to the start of the porting?

Was paint to barrel match .683?

Adjusting for the mag's shoot-up, it looks like length had a negligible effect on velocity consistency.

answers to most of these have been posted - read a few posts up.

paint to barrel match was pretty small - depending on the ball somewhere around .685. So, in this test we were not able to achieve the level of underbore we did in previous tests. That said, the bore portion of this test pretty much lined up with what we got last time. The new analisys available with this test is the length and one v two piece design.

Based on this testing - I DO think that a 14" small bore barrel will be the most efficient on any gun.

The emag we used on this test achieved a SD of under 2 fps on previous tests with a sample size of 20 - it's a fantastic, consistent shooting gun - and as I posted above - the reason the data is in ascending order is that I sorted it that way to knock off the highest and lowest.

[scc2052]

In the results I'm confused and don't really understand what the numbers on the graphs that are on they left mean can someone help me out? thanks

[brycelarson]

scc2052, on Dec 29 2008, 04:47 PM, said:

In the results I'm confused and don't really understand what the numbers on the graphs that are on they left mean can someone help me out? thanks

the two numbers that we're looking at for this test are:

mean velocity

and

SD (standard deviation)

mean velocity is a number that tells you how fast the ball was leaving the barrel. A higher mean velocity indicates that with the gun set the same - that barrel is going to shoot faster. This indicates that you could get more shots at a specific velocity from the same tank out of a barrel with a higher mean velocity.

Standard Deviation (SD) is an indication of how consistent that barrel is. the lower the number the more consistent. A low SD will directly correlate to having a lower +/- fps when chronoing a gun. Additionally, it's my assumption that a more consistent gun will be a more accurate one.

does that help?

[Poe]

It might also be worth noting the porting when referring to a barrel length as 'most efficient'. Wouldn't you have to test more then one gun to make that claim though? Try just shooting the emag with a higher or lower internal pressure and I'll bet you get a different 'most efficient' length. Maybe do a string of 'hot' shots by pausing between shots so the dump chamber can reach ambient.

The emag might be consistent with one type of barrel and paint, but as shown in the "dry fire vs paint efficiency test" backpressure can effect it's operation for better or worse.

Thanks for noting the sorting. That was really throwing me off.

[cockerpunk]

Poe, on Dec 29 2008, 08:38 PM, said:

It might also be worth noting the porting when referring to a barrel length as 'most efficient'. Wouldn't you have to test more then one gun to make that claim though? Try just shooting the emag with a higher or lower internal pressure and I'll bet you get a different 'most efficient' length. Maybe do a string of 'hot' shots by pausing between shots so the dump chamber can reach ambient.

The emag might be consistent with one type of barrel and paint, but as shown in the "dry fire vs paint efficiency test" backpressure can effect it's operation for better or worse.

Thanks for noting the sorting. That was really throwing me off.

if the goal however is pure shot to shot consistency that gun is so far the best gun i have ever seen in my 9 years now of playing paintball. it is simply amazing over the chrono. seriously, i have seen and shot them all, from AKA to DM and such, and that emag is amazing over the chrono. it is unquestionably the most consistent gun i have ever laid hands on. it beats my cyborg by at least 50%. the dry fire vs with paint does little in comparison to shot to shot consistency, that is a test that deals primarily with the pressure in the dump chamber when cycling normally, which, as long as the gun shoots consistent doesn't matter one bit.

would it have been easier that we simply shoot 3 times before each test and not record it? to me, it makes alot more sense to have a standard procedure like droping the high and low, a STANDARD manipulation of data widely accepted in experimental dings.

porting and length of back are factors, i'd agree there. the CP backs looked to me to be 4 or 5 inches long, but we can see the effect of 12, 14, and 16 inch "control bores" with the one piece test.

This post has been edited by cockerpunk: 29 December 2008 - 11:47 PM

[slinkyaroo]

CP - what paint were you testing at the time? What bore size was the paint?



.

[Lord Odin]

slinkyaroo, on Dec 29 2008, 10:46 PM, said:

CP - what paint were you testing at the time? What bore size was the paint?



.

They noted the paint in the top left corner of the data spreadsheet. It was DXS Silver with a .683-.684 bore size.

[kert.]

For more accurate 1-piece vs 2-piece comparsion, shouldn't you test with .685 back?

Awesome job tho!
Thanks!

[brycelarson]

Poe, on Dec 29 2008, 07:38 PM, said:

It might also be worth noting the porting when referring to a barrel length as 'most efficient'. Wouldn't you have to test more then one gun to make that claim though? Try just shooting the emag with a higher or lower internal pressure and I'll bet you get a different 'most efficient' length. Maybe do a string of 'hot' shots by pausing between shots so the dump chamber can reach ambient.

The emag might be consistent with one type of barrel and paint, but as shown in the "dry fire vs paint efficiency test" backpressure can effect it's operation for better or worse.

Thanks for noting the sorting. That was really throwing me off.

No, we don't have to test more than one gun to make the efficiency claim. A gun is a valve - how that valve gets air into the barrel is WAY less important than how the air interacts as the ball is accellerating.

I do see what you're getting at - maybe a steep slope on the power pulse would result in a shorter optimal barrel length? Maybe. However, the way a gun delivers air isn't going to radically effect optimal barrel length. On the Emag it's 14" Maybe we'll shoot the Cyborg on Friday and test 10, 12, 14, 16 again. Wouldn't take long - but I'm willing to lay money on the same results. Whatever the gun's power pulse looks like the ball is going from 0 fps to 300 fps in a very, very short time - and the distances that it takes to get to that speed are going to be very similar on all guns.

sorry about the sorting - I should have noted that from the begining

kert., on Dec 30 2008, 08:17 AM, said:

For more accurate 1-piece vs 2-piece comparsion, shouldn't you test with .685 back?

we did.

[Lord Odin]

brycelarson, on Dec 30 2008, 08:44 AM, said:

Poe, on Dec 29 2008, 07:38 PM, said:

It might also be worth noting the porting when referring to a barrel length as 'most efficient'. Wouldn't you have to test more then one gun to make that claim though? Try just shooting the emag with a higher or lower internal pressure and I'll bet you get a different 'most efficient' length. Maybe do a string of 'hot' shots by pausing between shots so the dump chamber can reach ambient.

The emag might be consistent with one type of barrel and paint, but as shown in the "dry fire vs paint efficiency test" backpressure can effect it's operation for better or worse.

Thanks for noting the sorting. That was really throwing me off.

No, we don't have to test more than one gun to make the efficiency claim. A gun is a valve - how that valve gets air into the barrel is WAY less important than how the air interacts as the ball is accellerating.

I do see what you're getting at - maybe a steep slope on the power pulse would result in a shorter optimal barrel length? Maybe. However, the way a gun delivers air isn't going to radically effect optimal barrel length. On the Emag it's 14" Maybe we'll shoot the Cyborg on Friday and test 10, 12, 14, 16 again. Wouldn't take long - but I'm willing to lay money on the same results. Whatever the gun's power pulse looks like the ball is going from 0 fps to 300 fps in a very, very short time - and the distances that it takes to get to that speed are going to be very similar on all guns.

sorry about the sorting - I should have noted that from the begining

Hmmm. Shouldn't an LP gun require a longer barrel than an HP gun? After all, its using less pressure but requires more volume. Wouldn't that necessitate a longer barrel to accelerate the ball up to field velocity? I would think that an HP gun accelerates the ball in a shorter distance and wouldn't require as long of a barrel. If that's true, perhaps you should repeat the test with an opposite pressure gun. I don't know if the Emag is HP or LP. Or do you think that the barrel length difference is negligible?

This post has been edited by Lord Odin: 30 December 2008 - 10:31 AM

[Snipez4664]

Those differences mostly get washed out in the valving, before the ball sees them. What we're really concerned with is the 'shape' of the power pulse that hits the ball - acceleration is part of this shape and the pressure tends to build much faster than the ball is accelerated - I would tend to disagree with bryce that the length will be totally independent of gun - think about it:

For a given efficiency gun, you need X amount of pressure*volume work to get to field velocity.

The point at which you get diminishing returns on the barrel length is where the pressure*area of a paintball is less than drag + friction. Generally this will occur at a given system volume, where the system is barrel + dump chamber+ pre-expansion volume. Note that for poppet guns or anything sealing the chamber, the dynamics get even more complicated and must be modeled in at least 2 steps.

I'd expect poppet guns to benefit from a shorter barrel, and spools to benefit from longer ones. The automag somewhat splits the difference (Tiny dump chamber spool). Welcome to my gross oversimplification.

[cockerpunk]

Snipez4664, on Dec 30 2008, 11:09 AM, said:

I'd expect poppet guns to benefit from a shorter barrel, and spools to benefit from longer ones. The automag somewhat splits the difference (Tiny dump chamber spool). Welcome to my gross oversimplification.

haha

so, do you think thats a large enough effect to notice? like measure in inches?

idk, i see theoretically where you are going, but i just dont think it will have a very large effect.

i would expect the porting pattern and whatnot to have a larger effect, for example. we saw that there was similarities with the dye barrels compared to the CP ones, even though they are ported and built differently. at the same time we saw some slight differences.

[Snipez4664]

cockerpunk, on Dec 30 2008, 12:39 PM, said:

so, do you think thats a large enough effect to notice? like measure in inches?

Hrm. OTOH, Glenn Palmer says it does. I remember him claiming he matches barrels to guns individually.

A barrel gives you what, 0.37 cubic inches per inch linear?

and you need, say, 115 in-lbs to fire the ball...that means a 150psi gun's dump chamber is what, 1 inch cubic, perhaps? I feel like that puts about a 3 inch cap as far as variance on the whole thing. I think it's probably one of those things that you could confirm with the right experiment, but it might now fall out naturally of others...Meaning as far as scale goes, we don't really care.

[paulpker121]

Wow, this further proves that underboring > overboring!

You guys have come a long way, congratulations on the sponsorships.

[brycelarson]

Lord Odin, on Dec 30 2008, 09:30 AM, said:

Hmmm. Shouldn't an LP gun require a longer barrel than an HP gun? After all, its using less pressure but requires more volume. Wouldn't that necessitate a longer barrel to accelerate the ball up to field velocity? I would think that an HP gun accelerates the ball in a shorter distance and wouldn't require as long of a barrel. If that's true, perhaps you should repeat the test with an opposite pressure gun. I don't know if the Emag is HP or LP. Or do you think that the barrel length difference is negligible?

the emag is HP - BUT, and this is a big but, operating pressure has very little to do with breech pressure. Breech pressure is more dependent on valve design.

We could certainly put a LP spoolie up against a HP poppet and see if barrel length changes. That would be an easy basement test. dunno if we'll have time to add it to Friday - we're already going to be busy.

[romulus333]

Lord Odin, on Dec 28 2008, 03:56 PM, said:

Compulsion, on Dec 28 2008, 03:14 PM, said:

What's with the wicked spiking on those first shots?

In many cases the first shot is 20 or more FPS higher than subsequent shots. Do you have creep in the gun?

This test might benefit from two or three clearing shots before beginning to take measurements. At the very least, remove those outliers from the calculations of Mean and SD.

That's the beauty of standard deviation. Outliers won't affect the SD as much as it would say mean or range. Picking and choosing which shots to include or exclude isn't a good idea. That can get you into all sorts of problems. Its better to just include all data and analyze it from there. Besides, the bell curve will always have outliers towards the extrema.

That being said, a few clearing shots might be a good precautionary measure. Especially if there are asymptomatic problems with a gun.

I would second that discarding outliers is problematic for validity, but using a certain number of clearing shots as a pretest operation would be a methodologically sound idea.

[Iram]

What is the operating pressure on that emag?

[brycelarson]

romulus333, on Dec 30 2008, 06:14 PM, said:

I would second that discarding outliers is problematic for validity, but using a certain number of clearing shots as a pretest operation would be a methodologically sound idea.

the highest was the first shot in every round of shooting and is listed first on each data set - if you want to crunch the numbers simply dropping the first shot - the data's ready to do that as well.

in fact, I just did that - the mean fps dropped a bit - the SD rose a bit - but consistently on all.

all rankings remain the same.

Iram, on Dec 30 2008, 06:15 PM, said:

What is the operating pressure on that emag?

CockerPunk can answer better than I can - but I think 650 / breech pressure somewhere around 80

This post has been edited by brycelarson: 30 December 2008 - 08:04 PM