Really Tight Bore?

[CDN_Stalker]

I had my KSC M11A1 inner barrel measured years ago my a professional machinist, it came up to around 6.14mm I recall.

Now, onto increasing the accuracy. Heavier BBs are a plus, but try this (works beautifully with the KSC Glocks, unsure of the USP though). With the mag out and the gun unloaded, look at the muzzle, and stick a pen in the inner barrel. See how much (if any) the inner barrel moves around, side to side, up and down. In the KSC Glocks, it was quite a bit, over 1mm deflection from center I think it was. I pulled the inner barrel out, found a thicker O-ring (holds the inner barrel steady inside the outer barrel) and put it in. Reduced the movement to much less than 1mm, more like 0.25mm by eyeballing it, but increased the accuracy by a huge amount, like 4" groups at 30ft with 0.25g BBs, compared to the 6" groups I'd get before.

[AngelusNex]

Originally Posted by mas_oyama

how does a rifled barrel works on an airsoft gun? I understand it importance on a real steel gun... but on airsoft... wouldn't it mess the back spin created from the hopup? it would mess both the accuracy and the range, wouldn't it?

the 'rifling' allows air to flow around the bb evenly rather than spin it like real steal, it's just air channels. It works with the hopup.

[mas_oyama]

Originally Posted by AngelusNex

the 'rifling' allows air to flow around the bb evenly rather than spin it like real steal, it's just air channels. It works with the hopup.

oh I see... So its not a channel that circles around the barrel, but rather some straight channels from back to front of the barrel? Cool. Thanks for the info!

[CDN_Stalker]

Not straight, they are in a spiral like a real gun's rifling. This, plus the hop up effect, causes the BB to rotate evenly on all axis, generating greater stability than the BB spinning on only one axis (X or Y rotation). Because of this, the rifled barrel is only effective up to 330fps (because it was designed in Japan, it has to follow the 1J max limit).

[Donster]

i remember reading that in the 6.01 barrels, the BB bounces around more in its motions (think of the wave length of gamma rays). with the 6.03, they bounce around less (take the same motion patter as radio waves). this leads to better accuracy. again, this is from what i remember reading. it was a long time ago.

[CDN_Stalker]

Interesting, actually makes sense, a BB will have a greater chance of touching the barrel walls in a 6.01mm, where a 6.03mm will allow more air to pass by the BB and provide a stabilizing cushion to keep it away from the walls. Am I close?

[ShelledPants]

My understanding was that:

The loose end of the spectrum (6.14mm) provides a safe medium for the multitude of ammunition variants. (Gun manufacturers don't know what ammunition you use, and thus need to appeal to a larger market of acceptability) While still maintaining acceptable accuracy and FPS.

The tight end of the spectrum (6.01mm) increases FPS (and fps consistency) by having less loss of air around the BB, but loses accuracy due to the BB having more contact with the walls of the barrel.

The middle ground, (6.03-6.05) has a better balance of accuracy with higher quality ammunition, and an FPS boost from the loose end of 6.14mm, without losing too much accuracy from being too tight on the BB, such as 6.01mm.

Please correct me if this is wrong.

I had a great experience with TK barrels in a 5.1 Capa shooting .3's, but I didn't like the results from .20s, there was minimal change from the stock barrel at lighter weights.

[coach]

Originally Posted by CDN_Stalker

I had my KSC M11A1 inner barrel measured years ago my a professional machinist, it came up to around 6.14mm I recall.

Now, onto increasing the accuracy. Heavier BBs are a plus, but try this (works beautifully with the KSC Glocks, unsure of the USP though). With the mag out and the gun unloaded, look at the muzzle, and stick a pen in the inner barrel. See how much (if any) the inner barrel moves around, side to side, up and down. In the KSC Glocks, it was quite a bit, over 1mm deflection from center I think it was. I pulled the inner barrel out, found a thicker O-ring (holds the inner barrel steady inside the outer barrel) and put it in. Reduced the movement to much less than 1mm, more like 0.25mm by eyeballing it, but increased the accuracy by a huge amount, like 4" groups at 30ft with 0.25g BBs, compared to the 6" groups I'd get before.

Good point. my WE P14 has a lot of play between the inner and outer barrel. But it's odd since during one game I hit Zeon 5 times on the same knee, dueling at 10 paces, in the span of 3 seconds! Pretty sure I was shooting from the hip too as it was a western game theme!

[m102404]

Tweaking pistols is a lot of fun...but frustrating because of the inherent limits.

There needs to be slop...enough so things don't bind. There can't be a lot of cam forces involved since GBBs don't work at real steel pressures/forces.

But too much slop and it's....sloppy.

Since...for the majority of pistols...the sights are mounted on the slide...which is independant of the outer barrel...which is independant of the inner barrel....what needs to be keyed in on is the consistency. Consistency = accuracy.

Your inner barrel can move around if you wiggle it...but if it always rests in the same place when in battery (e.g. comes to rest at 6 o'clock on the outer barrel)...then one source of variation between the direction of the bb and the sights is "removed". You'd be bloody lucky if it returned to the same spot 100% of the time...but most of the time is good enough for airsoft.

Forcing it into center (at repeatable spot that you pick vs. the natural state of rest for that particular pistol) with o-rings, rubber washers, tape, etc....works. The inner, on most, still needs to move back and forth and tilt a bit....so it can't always be just jam fitted inside. Once I get my lathe back from the in-law I'm going to try to machine up some derlin bushings.

The other point of variation up front is the position of the outer with the slide. There is very little to be done there without some major mods. Trial and error with different parts is very expensive....too expensive for me. Illusion probably does it because he's got volumes of custom parts. The outer should be fairly consistent in the slide...touching a reference point or not...because of the cams, lugs and "bolt" face at the rear. So like an unaltered inner...there's just hoping that it's returning to the same position at the end of each shot.

I dearly wish that manufacturers would build oversized outer barrels and undersized bushings so I could custom fit them...but I'm sure that's not mass market friendly.

My current race gun, has a 6" PDI 6.01mm and used to shoot thumbnail size 10 shot double tap groups from across the basement 25' or so with .28's traveling a bit under 300fps. Over time, it's opened up to about 1.25"-1.5" and I'm building a new rig.

Heavy quality BBs...clean long tight bore...good knocker valves on every mag (that's where another key source of consistency comes from)...tight hopup (so it doesn't work itself off).

[Donster]

Originally Posted by CDN_Stalker

Interesting, actually makes sense, a BB will have a greater chance of touching the barrel walls in a 6.01mm, where a 6.03mm will allow more air to pass by the BB and provide a stabilizing cushion to keep it away from the walls. Am I close?

exactly. that was what the article was talking about. i dont know the knitty-gritty, but that was the jist of it

[Azathoth]

Originally Posted by Styrak

You're not supposed to use them above 330fps. (won't do what it's supposed to)

It's doing Something correctly. When Tanio Kobayashi made these barrels years ago and was interviewed in a Japanese/Taiwanese Airsoft magazine on HOW they worked and Why he was unsure, but they work. I've done side by side comparisons in my P90 using bench mounted vices to see if their is a noticeable difference in performance between the TK and a prometheus, and KN barrel @ P90 lengths. Their basically no difference in groupings between the 3 barrels out to 100 ft.

I don't know why it works, and honestly I don't care. If the person who designed the barrel can't answer the question either.. @ 400 FPS the gun that I own shoots just as good with any of 3 big brands of tightbores. I've seen similar results with another gun and 363 TK barrel vs prometheus. Their is no Harm in this either. I'm surprised other users haven't bothered to try it.

Originally Posted by CDN_Stalker

Interesting, actually makes sense, a BB will have a greater chance of touching the barrel walls in a 6.01mm, where a 6.03mm will allow more air to pass by the BB and provide a stabilizing cushion to keep it away from the walls. Am I close?

Supposedly this is how it works on the TK twist. But I don't see any reason why the rifling angles to bullet needs to be at "X" joules for the barrel to work. As far as I know Tanio Kobayashi replicated the ratio of twist against a Real steal barrel.

[Donster]

Originally Posted by Azathoth

Supposedly this is how it works on the TK twist. But I don't see any reason why the rifling angles to bullet needs to be at "X" joules for the barrel to work. As far as I know Tanio Kobayashi replicated the ratio of twist against a Real steal barrel.

the rifling is used to channel air around the BB to provide a stable flight path. the rifling was designed to work best with 1 joule worth of air energy. that is why when people try to lower their FPS using heavier BBs, it has no effect.

[Dynamo]

Originally Posted by Azathoth

Supposedly this is how it works on the TK twist. But I don't see any reason why the rifling angles to bullet needs to be at "X" joules for the barrel to work. As far as I know Tanio Kobayashi replicated the ratio of twist against a Real steal barrel.

the twist rate of the TK barrel is not anywhere near RS.
the two barrels i have has a twist rate of 1 in 16 inch, a RS barrel is normally between 1 in 6 inch to 1 in 9 inch.
the TK barrels are designed for the Japanese market, running higher FPS makes the barrel work like any other tight bore, but you will loose some FPS due to the extra air bleeding around the BB.

[808]

/facepalm

Many of you REAAAAALLY need to read this article:
http://infectedairsoft.wordpress.com...-inner-barrel/

m102404 posted this earlier. I refer everyone with these questions and (in some cases) misconceptions to this article for a read.

Some you are right on the money. BUT - If you're not clear on it yet - just read the article at Infected Airsoft's blog. It will be worthwhile...

...I promise.

[Kos-Mos]

Originally Posted by Donster

the rifling is used to channel air around the BB to provide a stable flight path. the rifling was designed to work best with 1 joule worth of air energy. that is why when people try to lower their FPS using heavier BBs, it has no effect.

Not far, but not exactly.

The TK barrels work well at low FPS because the air PAST the BB won't skip the grooves and stay in the lines.

When you shoot a normal barrel, the BB hits a wall of turbulence at the exit because of the pushed air in front of the BB and the air around you.

In TKs, some air is leaked around in the grooves, but since it does not skip, it creates a spiral of air at the tip of the barrel. This acts as a barrel extension that would give progressively less support. It helps stabilizing the BB a lot because there is to shock or wall hit by it when leaving the barrel.

The reason it works less efficiently at higher FPS is because the air will skip teh grooves when past the grooves. It won't work worst than a 6.04 barrel though.