Rifiled Barrel in a GBB
 

I been looking around for hicapa parts have I have seen some rifled barrels. Obiously in a real gun, it has a purpose, but with a GBB, wouldnt it just null the hopup?

maby illusion could shed some light on this.

Spin Doctor
 

While most projectiles will rise a bit regardless, the type of spin has an impact on the overall flight path.

Spin "inline" with the trajectory will lend itself to rather curved (high in the center) trajectory, where as spin perpendicular to the trajectory will flatten it out.

Spin will stabiliize a symetrical object, but true rifling would be an increadible drain on velocity as the BB would have to contact the rifling to spin the BB, that's friction and that's no good.

That and the fact that the BB doesn't actually seal against the barrel, it rattles around (without hopup) or "crawls" (with hopup).

No seal means the rifling wouldn't grab the BB to spin it at all.

I have heard about the rifling spining the air as it travels down the barrel, and the "spinning air" then spins the BB.

Probably just cosmetic.

Hop seems a whole lot simpler...LOL

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.

Well, if I had to hazard an educated guess I say it would negate the standard hopup effect. The reason I say this is because for the rifling to work they need to grip the bb, this would prevent the bb from getting / keeping the back spin from the normal hopup. While this may increase accuracy (it's a bb...like it has any to begin with ;-) ) you will not gain the extended horizontalish flight distance that the hopup imparts on the bb by way of the back spin.

True, it would have to be one or the other....

As far a decent barrel and well fitting ammo? I agree again, the Gov'ment would be all over it. That and the fact that to defeat friction, you'd have to start putting some real force behind it..

And who could actually afford all that extra engineering and tollerance cost?

They're friggin expensive enough now!

Tanio Koba sells rifled GBB barrels, and has been for years.

Technically, these barrels are called "twist barrels", as they do not serve the same purpose as rifled barrels (most likely, the barrel you are refering to was made by Tanio Koba).

They work only by stabilizing the BB in the center of the barrel giving it more consistency and accuracy. It does not impart spin on the BB; the gases that pass through the rifling are what help stabilize the BB in the center. Thus, hop-up is not affected at all. It basically allows the BB to exit the barrel with backspin while not allowing it to touch the sides of the barrel.

And what class would it then become? It is still airsoft and still shoots under 500fps, so what would rifling possibly change? Pellet guns have rifling, I dont see them under some special class....

Rifled ASG barrels cannot impart a barrel axis spin in conjunction with a perpindicular hop up spin. An object can only store spin energy in one particular axis (not necessarily the standard vert-horiz-depth orthogonals).

I strongly doubt that a twist barrel can impart a consistent axial spin without engraving a pellet as a firearms barrel does. The force of friction sliding down a non cutting barrel surface is not very high. It's hard to imagine that one could impart a spin that could effectively stabilize a projectile without engraving the projectile.

For a rifled barrel to stabilize a bullet, it has to impart a very fast spin. For example a Glock barrel imparts about one rotation in 10". At about 4.5" long, that's only 0.45 rotations for the entire barrel, but the bullet leaves at about 1300fps which works out to a bleeding spin rate of 1560 revolutions per second when the bullet leaves the barrel.

Conversely a GBB pellet leaves an equivalent length barrel at a piddly 300fps. To acheive an equal spin rate, you have to acheive almost two rotations in 4.5" which is a significantly steeper helix.

Pretty hard to imagine a non engraving barrel not robbing a pellet of a significant amount of forward work energy and imparting a useful spin rate. We're also working with ABS pellets which a tiny fraction the density of lead slugs. You'd have to get an even higher spin rate to acheive stability.

The Tanio Twist barrels have their place. Mainly for use in non-hopup high-velocity IPSC race pistols. That kind of thing is more popular in Asia than it is here though.

Now that Madmax has clarified what I read earlier - there was a fairly in depth examination of the whole "spherical projectile" thing, done by the guy(s) who created AGD (airgun design - "the automag").

Basically, the experimental evidence suggests that the largest factor in terms of "inaccuracy" in spherical projectiles is due to the chaotic turbulence they experience as they travel through the air. Something to do with "The Random Walk".

With respect to paintball, I guess the larger surface area and relatively slower speed etc, etc. contribute to a visibly large random spread at X distance, where with airsoft, it shows up differently, probably due to the drastically different projectile size/weight.

It still shows up (turn your hop-up off, or just on enough to get a bit of a flat trajectory, and there's a cone shaped pattern of the BB paths), it's just ... smaller.

That, and hop-up is the only thing I can think of that WOULD possibly cause a BB to spin enough to stabilize it.

In any case, I guess the point would be that you're not probably going to get a worthwhile advantage with a rifled Airsoft barrel, any more than you would with a very finely polished smooth bore and a well-aligned hop-up.

I have yet to see a comparison of groupings between a well tuned no hop up GBB and a TK twist barrel. I also find it wierd that nobody offers close tolerance slide and outer barrel kits. If you really wanted accuracy, you'd make your outer barrel close in diameter to the slide to reduce OB-slide play. Then you'd also closely match the diameter of the inner barrel to the OB to reduce IB-OB play.

All in all, it'd make sense to spring both the OB upwards (or downwards) against the slide for consistant registration, to the slide, and spring the IB against the inside of the OB.

It's also kind of bad that the slide has some play against the frame. The rear end of the IB is firmly secured into the lower frame which means that about half the variance in the impact point is a result of slide-frame play (lift the tip of your slide and you lift the tip of your IB). The sights are mounted to the slide so slide-frame play results in a variance in impact point relative to the slide (hence the sights). It's very difficult to make a zero play slide action (barring a goofy Sherrif bearing arrangement), so it make sense to install a spring system to bias the slide high (or low) so it at least registers the same way consistently so the rear of the IB relative to the slide ends up in the same place.

I'm not sure I have all that much faith in HK gunsmiths. They should be publishing grouping comparisons between stock build vs. their own changes if they were really in the biz of performance IPSC. Instead all I find is nice pics of custom cosmetic milling. Lots of projectile voodoo like TN or twist barrels, but when I look at my Hicapa with an aftermarket "Kimber" slide, I note about 1mm of play between the OB and the slide. The IB is closely matched to the ID of the OB at least (stock TM). 1mm play at barrel tip equates to about .4" of grouping variance at 33' (~10m). The slide adds about a further 1mm of angular play (lift at the front) which maybe doubles the barrel related variance to 0.8" at range of impact.

Tightening a group at 33' by 0.8" is a bit of a big deal really. I used to shoot target pistol a bit and could consistently break a score of 85 without too much practice (not really a big deal). A 0.8" reduction in group would push me past 90 consistently. 0.8" is the difference between a lot of outside of the "X" ring hits I I'm guessing IPSC score is similarly strigent.

Before chasing down the ephemeral effect of axial spin stability, it makes more sense to acheive consistent lockup, between boresight point and sight point, when the slide goes into battery.

A friend of my dad's had a conical 'cap' or ring put on the very tip of his Beretta barrel, just for that reason. When the slide returns to battery, the hole in the slide "rides" onto the cap, forcing everything to lock together with a tiny bit of tension, and always to the same place (well, fairly close).

It reduced the movement of the barrel from visible and audible to pretty much nil.

I'm not sure how he got it done though, since the tip of the barrel had to be threaded, and any gunsmith who says "ok" to threading the tip of your 9mil. is a little shady.

It's permanent now though, I believe.

Anyways, all I was saying with respect to the 'rifled barrel" question was that it's really not the first thing to worry about with respect to getting good accuracy out of a GBB.

Your dad installed a lockup cone to pull the barrel forward and centre it to the slide bore. A pistol recoil spring is pretty stiff so it can push past a close fit cone pretty easy. I'm guessing the cone is lightly threaded onto an outer thread on the barrel i.e. shallow thread.

Threading the outside of the tip is probably fine. A handgun OB is conical so the wall thickness is highest at the outside. Lots of metal to thread into before you start to approach the root diameter close to the breech.

I think the barrel pressure exerted at the tip on R/S would be lower than at the breech due to a larger volume behind the bullet too. I'm not sure about that though. Powder burns at a rate/profile which may maintain a constant pressure behind the bullet.

Pellet guns are sold under one set of laws, airsoft under another. It's too long and weird to explain as most gun laws are insane.
You wind up with a Replica with a 'rifled' barrel. If the velocity reaches a certain point, it goes into the Pellet gun or the firearm class. It can even go into the firing replica definitions.
Huge can of worms.
I was interested for a while until I started to dig into the conflicting rules. Got a headache, and bought a real rifle instead.

Dimples?
 

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...

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.

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.

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.

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!

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

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

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)

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.

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...

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.

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
http://www.wgcshop.com/WGC_Shop/images/tk_pt_htbak.jpg

Illusion, have you ever used one in an AEG?

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

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.

I installed mine today in my KJW Sig P226 and it shoots really really sweet. I can't describe it other the the fact that it is straight and flat... like how everything should shoot. It's well worth the money I gave to Brian. That's for sure. I'd say it's probably the best upgrade I could have got for my gun performance wise.

I give these barrels 5 thumbs up... and I really only have 2 thumbs so the other two would be my big toes... and the fifth "thumb"... well... you can figure that out.

I'll put my 5 "thumbs" in as well to make it a total of 10.

If I could get them for every single one of my 80 million guns, I would.

As an interesting side note, I have a REALLY old school MGC Glock 17 Seidler Custom Race Gun and it doesn't have hop up, but it does have a rifled barrel. Range is crap, but the effective range it does have is very accurate.

I'd be interested to see about getting one for my AUG and my M700 if it's possible to find them. Please Illusion, keep us posted if it works out for that AEG.

oooo, on Power Edge they have these things for the VSR Gspec. Doesn't say what the optimal power would be though.

Looks like power edge has more barrels the WGS, and alot are in stock too.

ever seen a crossman colt model befor looks like a real gun mag pops out and in just like the real thing and it has a rifled barrel. I know for a fact that my counties law states that any object that has a barrel and receiver wich is ment to fire a projectile and is used in a crime is considered a firearm....dont ask

FYI

Can someone translate all that into English? I broke my brain trying to read it.

We're not using them in crimes.