Clear Barrel Experiments

[Blackthorne]

Originally Posted by ccyg8774

Are you going to colour the BB in some way to monitor the spin of the BB in the barrel? Or just study the "touching" between BB and the barrel?

Spin is out of scope for this first round of tests. We do have our hands on some BB's that are two colored and "swirled" that could be used to track rotation.

Originally Posted by m102404

Obviously you're aiming to catch the bounces in flight vs. examining evidence of a bounce post shot.

Yes. Anything past the muzzle is out of scope.

Originally Posted by m102404

In a good setup my bet is 2 bounces...first right after the hopup nub...the second close afterwards and then I'm guessing it's stabilized and/or doesn't get a third bounce before it's gone from the barrel.

You bet is laid. I will be keep track in a separate spreadsheet.

My own bet is it close...one strike after hop is applied and then no contact for the rest of the journey

Originally Posted by m102404

You could cheat and coat the inner surface of the barrel with a thin flim (say Molybendum)...then shoot a bunch of shots and look for discolouration patterns (it'll turn more silver as it's impacted). You could also capture BB's after the shot and if they had black marks on them then they've hit the barrel somewhere.

You don't even need a clear barrel to see that...just don't get any on your hopup rubber. I'd see coating the entire barrel...then cleaning the first inch of it (or just past the hopup cutout)...then assemble, clamp you gun in a vise and shoot. You can get powdered Moly at shooting places.

While not our primary approach, this is something we considered and will be doing (thanks for the tip on the moly). And while you don't need a clear barrel for the test it would make thing much easier, as the pattering could be observed in real time by simply looking at the barrel. Not to mention not having to capture BB's without disturbing any residue they may have picked up on the flight

Originally Posted by m102404

I'd stay simple and just setup for one set of tests....one standard barrel length (say 363mm) with 0.20's @ 350fps. Detail and publish the test setup and results and put it out there for peer review. Filter through the reviews and adjust testing from there.

Best of luck with this.

Cheers!

[Dynamo]

if you plan to use any liquid on the outside of the barrel, i would suggest mineral oil. it has a very similar refraction index to most glass materials and would almost completely remove the refraction of the outer wall of the barrel, but you would still have the inside surface to deal with.
making an acrylic/polycarbonate box around the length of the barrel, with a hole on both ends to seat the barrel would be real easy.

[Ricochet]

My bet is the BB contacts the top of the inner barrel near after hop-up and stays there for a few centimeters, then levels out.

[ThunderCactus]

Just in front of the hop rubber is where I notice the usual wear spots.
My dirty stock G&P M249 barrel has hits all over it though, I've managed to completely foul two barrels so far, you can see BB strikes all over inside lol

[Ricochet]

I wonder if that is caused by the ROF. The next BB may be interrupting the air seal. Either that or the hop-up may not be consistent.

[MaciekA]

The two most intensely burning questions I can think of answering in this study are:

First, (as others have mentioned and you'll surely hear about on Airsoft Mechanics), the effects of barrel length are extremely interesting. Once volume has correctly been matched to the cylinder and correctly accounted for relative to the strength of the spring, is there any effect whatsoever in lengthening the barrel beyond the exact match implied by the (port-adjusted) volume of the cylinder?

Second, and I'm pretty sure everybody in the airsoft world wants to know the answer to this one: How exactly does R-Hop work, and what does the empirical evidence in your study suggest about potential improvements to the R-Hop design?

edit: Also, a huge thank-you for taking on this work. This is going to be awesome.

[dogtoy]

Ive always thought about that , i had always figured that the bb must bounce around in the barrel on the way out & that because hop ups wear & backspin is introduced that they touch the hop as well , of course there maybe things going on we cannot see which is why this will be so interesting

[invisiblehand]

Have you considered adding smoke to see the movement of the air? While this isn't directly related to the hopup, it would help to show if the BB is being held off the walls of the barrel by the air cushion?

[Cpt- Lovegrove]

i hope you plan on releasing a video of the tests especialy of the highspeed shots, i would love to see them

[ThunderCactus]

Originally Posted by MaciekA

First, (as others have mentioned and you'll surely hear about on Airsoft Mechanics), the effects of barrel length are extremely interesting. Once volume has correctly been matched to the cylinder and correctly accounted for relative to the strength of the spring, is there any effect whatsoever in lengthening the barrel beyond the exact match implied by the (port-adjusted) volume of the cylinder?

Like I've said before, there's a maximum range and accuracy that can be achieved with a given weight of BB
Once you've topped out the performance capability of the BB, nothing you do to the gun is ever going to make that BB fly further or straighter.

So with any BB your optimal relative velocity is around 320-350fps, any faster and it destabilizes too quickly, any slower and you're just not getting the most out of it.
Once you hammer out barrel, volume, and compression requirements, the only thing left is barrel length. It's just a question of at what point does the BB stabilize itself within the barrel. For GBBRs and pistols, that's about 80mm or so, much more difficult to tweak with GBBRs since longer barrels tend to raise fps, which requires heavier ammo, which in turn raises the muzzle velocity even more.
AEG's tend to stabilize perfectly around the 420mm mark. Any barrel beyond the point of stabilizing is just useless metal. It's allowing more time for the BB to be DE-stabilized by potential fouling in that barrel.
Two VSR-10s built exactly the same internally, one with a 650mm barrel and one with a 420mm barrel, both shooting .3s, or one at 380 and one at 470, or 470 with .36s vs 440 with .3s, doesn't matter what combo we use, the 420mm barrel was never bested by the 650mm in terms of accuracy.
In fact, the 650mm barrel had worse accuracy when using .3s at 470fps

The idea that longer barrels increase accuracy in airsoft was carried over from real steel, but the physics of the two are completely different.

[Ricochet]

This is true, I've seen Frank's gun in action; as well as specific examples of shorter barrel length being an asset. I do have a theory though. The bigger the bucking, or should I say the "harder" the spin put on the BB, the more a longer barrel will help by allowing the BB to stabilize. I've noticed very distinct differences between how spring, GBB, GBBR, GNBB, AEG, PTW react with distance, accuracy, BB weight, barrel length, etc. Though the concept is the same, slightly different aspects can affect things greatly.

[ThunderCactus]

I figure the reason a GBBR always outperforms AEG's and PTW's in it's ideal temperature range, is because the BB hits the hop rubber at a higher speed, getting better spin off it, and the significantly higher pressure from gas allows the BB to stabilize much faster.
Because a gas pistol shooting .3g BBs at a relative 240fps, always shoots better than an AEG shooting .3g BBs at a relative 240fps. Most likely because the pistol imparts better hop on the BB

[mcguyver]

Is it not possible to place a dye on the BB that will transfer to the barrel when shot?

This would indicate relative speed of the BB vs. direction of travel inside the barrel and the force of impact with the barrel.

This of course assumes that the BB will actually touch the inner barel at all. But we do know from many years ago that BBs with a poor surface finish would leave streaks of their finish inside some barrels.

[m102404]

There was those "marker" bbs a while ago...the one that made a mess of everything. Not the ink ones...the ones that had some sort of powder finish

[Styrak]

Originally Posted by m102404

There was those "marker" bbs a while ago...the one that made a mess of everything. Not the ink ones...the ones that had some sort of powder finish

Yeah, Game Face BB's I'm pretty sure.