Rifiled Barrel in a GBB

[Blackthorne]

I think this may have been discussed before, but I want to get your spin on it in this context MadMax..

Is there any substance to the idea of Golf Ball dimpling being applied to BB's, not taking into accout the ability/cost of having them manifactured?

Does that kind of approach to drag management scale down to the BB sized sphere?


***EDIT***

Found it on my second search...

Originally Posted by CDN_Stalker

Been discussed, no. Someone on Airsoft Retreat asked once, and it's just not practical due to the light weight of BBs (compared to golf balls) and that golf balls are lobbed (as opposed to going horizontal to the ground).

Still tho...be interesting to test...

[ert]

I have a TK twist barrel on the way for my 226. I'll swap it out with my stock barrel and give you guys the results after a few tests.

[Gryphon]

Originally Posted by Greylocks

It would nullify the hopup immediately, and change the legal class of the handgun.
There's a big step from smoothbore to rifled, and what it can mean.

Rifling has absolutely no relevance in the eyes of the law. A firearm is defined by the Firearms Act as "a barrelled weapon from which any shot, bullet or other projectile can be discharged and that is capable of causing serious bodily injury or death to a person" with the usual exemptions for air guns, etc. Says nothing about rifling.

[JourneyMan]

I've seen a discusion about these barrels on another BBS.

They are designed to keep the BB floating in the exact center of the barrel, without it touching the sides. In doing this, you will lose about 20 fps from a traditional barrel, and improve accuracy. The whole system is designed to operate at ~320fps, so its a no go for snipers unless TK designs a new set of barrels sometime.

These barrels are made for AEGs as well, look on WGS and Power Edge.

[MadMax]

I think dimpling would hurt on bbs. There's a significant size difference between a golf ball and a 6mm pellt. Dimpling may have a different effect on larger or smaller balls.

It is convenient that a well struck golf ball has a speed not too far off from an AEG though (~200+fps). Say you are Tiger Woods and blasted a ball at 300fps equivalent to the KSC Glock in your Safariland.

The 300fps airsoft pellet has a speed-diameter ratio which is 6.85 higher than the golf ball (6mm vs. 41.15mm). The reason I'm getting into speed-diameter ratio is I'm getting towards an important number called the Reynolds number.

I just found an online Reynolds number calculator:

http://www.processassociates.com/Pro...men/dn_rey.htm

If you want, find the density and viscosity of air and you can plug the diameter and velocity of your projectile to crank out a reynolds number.

Golf ball Re: 26,680
bb Re: 3890

The 300fps pellet flies in an entirely different Reynolds number regime not too far off from the laminar/turbulent area that a butterfly flies in:

http://hypertextbook.com/physics/matter/turbulence/

The Reynolds number is dimensionless and is more or less widely applicable. While a butterfly doesn't fly at a 300fps, it's larger wings crank up it's Re significantly. Larger objects moving slower experience air as a viscous substance. Laminar flow forces play an important role. The small size of the pellet reduces it's Rn so it will experience air's laminar flow properties more or less as a butterfly will. Because not much air is displaced very quickly, viscous behavior has a greater effect than the overcoming the inertia of air molecules.

Conversely, the much larger golf ball has to displace more air as it blasts through the atmosphere. It's larger charactaristic diameter experiences the inertial effects of air molecules having actual mass significantly. At Re=26680 you're much closer to a turbulent transition point so dimpling can help shed an attached flow and further reduce viscous flow effects. Turbulent flow exerts less resistance than laminar flow in the golf ball Re regime.

I think at Re<5,000 laminar flow is too well attached to be effectively shed by dimples. Instead attached flow will exert more viscous flow drag as it has a more convoluted surface to slime around.

You also have the hopup-bb consistency issue to deal with. I suspect that a dimpled bb will take a spin from a hopup with less consistency than a smooth one depending on how the pellet is oriented relative to the hopup nubbin. You also probably have funny rolling effects in the barrel with unsmooth pellets too.

Man Google rocks!

Originally Posted by Blackthorne

I think this may have been discussed before, but I want to get your spin on it in this context MadMax..

Is there any substance to the idea of Golf Ball dimpling being applied to BB's, not taking into accout the ability/cost of having them manifactured?

Does that kind of approach to drag management scale down to the BB sized sphere?


***EDIT***

Found it on my second search...

Still tho...be interesting to test...

[Shinjin_MC]

ive just looked over a KSC MK23 2005 ver.
the inner barrel has this spring-loading thing which pushes it up against the top of the outer bbl; its a very simple mechanism that would be easy to replicate on any gbb with nothing more than a drill
the front i.bbl still has a bit of play and the o.bbl doesnt sit PERFECTLY into the slide, though

[The Saint]

Originally Posted by Gryphon

Rifling has absolutely no relevance in the eyes of the law. A firearm is defined by the Firearms Act as "a barrelled weapon from which any shot, bullet or other projectile can be discharged and that is capable of causing serious bodily injury or death to a person" with the usual exemptions for air guns, etc. Says nothing about rifling.

Have to keep those anti-loyalists from building up a revolutionary stock of smoothbores somehow.

[Mysteryfish]

Heheh, Madmax, I just meant threading the end of a handgun barrel makes me immediately think of suppressors, so I would have thought it harder to get done (here in good ol' suppressor free Canada)

[lt_poncho]

The MGC Beretta 92f NBB was one of the first to use a rifled barrel - they called it the 'cyclone' barrel, and claimed it helped accuracy, which I find it did. When GBB's came out, the range was pretty minimal compared to most Airsoft, and with the advent of the hop up unit, accuracy was in the inner diameter of the barrel. A rifled GBB barrel, add to that tightbore - would make a very accurate pistol.

Didn't a french BB company dimple their BB's? I have a bottle of those at home - apparently they were quite expensive but they did have dimples, you need a magnifying glass to see them. I can't remember the name of the company.

Originally Posted by Greylocks

It would nullify the hopup immediately, and change the legal class of the handgun.
There's a big step from smoothbore to rifled, and what it can mean.
With a decent barrel and well fitting ammo, who knows? But it certainly would not have a hopup anymore. It would not need it.

If I remember when I looked into it, the smoothbore was picked to reduce the legal headaches.

I just got a headache reading this...when did Airsoft manufacturers ever give a shit about Canadian laws? I rifled my coffee cup and i'm still not in jail, by the way...

[Greylocks]

Originally Posted by Gryphon

Rifling has absolutely no relevance in the eyes of the law. A firearm is defined by the Firearms Act as "a barrelled weapon from which any shot, bullet or other projectile can be discharged and that is capable of causing serious bodily injury or death to a person" with the usual exemptions for air guns, etc. Says nothing about rifling.

Dig deeper. And keep in mind at all times when you dig that there are tons of interpretation goofs they can make along the way.
If whoever decides to pick at you is in a bad mood, imagine the kind of shit they could give you over a rifled full auto gun (of any kind)?

It makes no sense, I fully agree there, but there is nothing stopping an overzealous paperpusher if they want to cause grief. You'd probably win your case, but the question here is; do you want to go there? Is it worth testing it?
I've seen my share of stupidity when I had to deal with real guns; stupid laws, even more stupid "policies". It's the latter you must watch for, as they are rarely posted anywhere.

So, what can I say except tell you what I found out, or saw, in the past? Maybe they dont care anymore? If yes, thank god.

[ILLusion]

Okay. We've ALL heard the theory, and have the idea that the projectile trajectory will be thrown all wonky.

Practical experience says otherwise. I couldn't believe it when I first shot it... I have NEVER seen ANY airsoft gun (my long range guns included) shoot a BB so straight for so far.

The higher up you turn the hop up, the further the BB will go before it drops.

It doesn't have the classic "hop-up arc" that you'll see with a standard barrel and hop up on.

I'm not going to argue theory.

I'm just telling you the TRUTH.

There's a reason why I have them in all of my GBBs


PS: Tanio Koba barrels are rated for guns that shoot no more than 1 Joule. I imagine this is because the rifling is a bit too tight for any higher velocity. It may skip grooves.

Thats what I thought. When UNcompany sells their custom and special guns, they usually have top notch parts, and I saw the TM hicapa 4.3 with a rifled barrel and thought it must be there for something. I just never thought it would work with a hopup. but since illusion claims it does, Im guessing there must be a reason we dont have rifled barrels for AEGs?

actually, it was a WGC custom gun i saw it on, but i searched WGC for Tanio-Koba and found all kinds of stuff

Rifle ring groove in the inner surface
- Combines hop-up and gyro spin to obtain higher accuracy
- Fits Marui AK47 / G3 Series


Illusion, have you ever used one in an AEG?

[HaZarD SFD]

Hmmm.. Looks like that would be one sweet barrel in a AEG Droc. I see a group order
in the near future

[ILLusion]

Not yet, because it's been near impossible to get any.

When I'm in Hong Kong next month, I'm going to grab whatever I can. I'm curious as to how it would work in a 400fps AEG.