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.

[Blackthorne]

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

[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.

[Digital_Assasin]

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.

[Blackthorne]

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.

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!

[Mantelope]

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

[WhatTheWho]

Originally Posted by Droc

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?

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.

[Ghost Snake]

Originally Posted by Greylocks

It would nullify the hopup immediately, and change the legal class of the handgun.

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....

[MadMax]

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.

[nic_s]

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.

[Mysteryfish]

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.

[MadMax]

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.

[Mysteryfish]

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.

[MadMax]

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.

[Greylocks]

Originally Posted by Ghost Snake

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....

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.