[WihanZA]

So I haven's been an active player for about a year now, but trying to make room in my schedule to play again. Before I get back to playing though I would like to sort out my Type 96's fps inconsistency issues.

The setup:
- Base: ASG AW308
- AirsoftPro EZ trigger
- Action stainless steel cylinder
- Action cylinder head - modified to seal with vsr buckings + mousepad as sobo pad
- Laylax/First factory piston & piston cup
- Laylax/First factory spring guide & SP150 spring
- Stock hop up unit - modified to accept vsr buckings
- Lonex 70 degree VSR bucking - teflon taped to barrel
- TDC
- R-hop - 7.5-8mm in length
- 510mm 1714 easton eclipse arrow shaft barrel
- 1 piece barrel spacer - combo of aluminum pipes and insulation tape (locks barrel perfectly)
- WE 0.4g Tan bbs - washed with dish washing soap
- Xcortec X3200 chrono
- FPS : 316 - 337 fps with 0.4g bbs

Currently the cylinder group provides perfect air seal. I can cock the spring, cover the cylinder head nozzle with my finger, fire, hold for 2 minutes, and when I remove my finger a large gush of air leaves the cylinder and the piston hits the cylinder head.
The same goes for the cylinder head to hop up bucking seal. I can cover the barrel with my finger, hold for 2 minutes, and a large gush of air leaves the barrel if I remove my finger.

The rifle is approximately 2.5 years old, have gone through an evolution of parts and at no point was the fps consistently within 10 fps.
Parts that I have had installed in the gun during the past few years: (these have been cross interchanged with current and stock parts)
- Stock KWA 6.05mm barrel ER hopped (12mm) - unpolished and polished
- AirsoftPro Type 96 hop up unit + guarder 70 degree aeg bucking
- AirsoftPro Type 96 Steel cylinder group, piston and spring guide
- AirsoftPro Type 96 M170 spring (standard and shortened)
- Stock cylinder, piston spring and spring guide (with new o-rings with perfect air seal)
- Stock hop up unit with stock bucking and r-hop
- 510mm 1714 arrowshaft barrel with 12mm ER Hop

Horisontally, the rifle is very accurate (approximately 8 cm horizontal grouping at 30m). Vertically though, there are a lot of flyers. At 30m, 50% of the shots will land within a 10-15cm vertical grouping, but the other 50% hits within a 40-60cm grouping. This drives me crazy. I am despondent. I have tried everything that I can think of.

Currently the fps seems to fall into 3 categories:
- 316-318 fps with 0.4g bbs
- 325-329 fps with 0.4g bbs
- +-340 fps with 0.4g bbs

I am lost for words and would appreciate any help

 

[Reliku]

The only source of trouble I can think of are the bb's. If they have an inconsistent diameter then they will yield inconsistent fps. The thickness of a hair in diameter can already lead to +20 fps difference. Have you tried other bb's?

 

[newcomer]

Xcortechs can get funky readings at times. See if you can borrow an F1 Chrony to verify if the readings tally up. Alternatively the MK4 combro is very accurate and not too expensive. I use the latter.

 

[WihanZA]

I did a chrono and quick accuracy test with my bar 10 and the same WE 0.4g tan bbs.
The Bar 10 has a stock cylinder, piston and spring (only replaced the orings) and a r-hopped 1714 arrowshaft barrel with a similar spacer.
FPS was 285-291 fps with 0.4g bbs, which is much more consistent than the L96.
There were also a lot less vertical deviation in shots at 30 meters. (+- 20 - 25cm).
IMO this rules out the ammo. Yes it might cause a 5 fps deviation, but where does the other 15 fps deviation come from? :shrug:

 

[Reliku]

And what about a different spring?

If all the energy that's in the spring goes into the bb's (perfect airseal) and all bb's are more or less identical, then that must mean that the energy in the spring changes.

Which I don't think is possible, but just to show something odd is going on.

There was a question a couple of days ago about someone who had three different springs, perfect airseal and all different springs would produce the same fps.

Much like your case, I don't know what's going on, but somewhere you must've gotten something wrong.

Either that, or you've busted all of physics and invented the perpetuum mobile.

 

[WihanZA]

Good news! Modern physics is still intact and the fault for the major inconsistencies is not all mine.

I have used 3 different springs before posting here as it was already one of the many possible problems I could think of, but the major fps and hop up inconsistencies were still there.

This lead me to believe that only one of two things can possibly still cause inconsistencies.
Either there might be something wrong with the trigger mech, as it might be releasing the piston inconsistently, even though it appeared to operate smoothly.
Or the outer barrel might be moving from shot to shot.

Seeing as a new trigger unit would set me back at least another $100 I tried to figure out if the outer barrel might be the problem.

The ASG AW308's outer barrel does not screw into the receiver. Instead it uses a unique locking mechanism. I have already ensured that there is no wobble in the outer barrel when attached to the receiver and when the entire gun is assembled. I free floated the barrel to try and ensure that the stock does not influence the outer barrel's position.

Eventually it turned out that the stock flex in the magazine area was bad enough that the stock still managed to press up against the outer barrel when using a bi-pod and when I pulled on the bi-pod to bend the stock away from the outer barrel, vertical shot consistency greatly improved and I can now very consistently hit (approx. 8/10 shots) a 7x15 cm empty bb bottle at 30m.

I know this is a bit of a wall of text, but this might help someone else who have been struggling with a rifle's consistency and that have run out of explanations for their problems.
When I say the stock flex is bad, it's only flexing about 0.5 mm to 1 mm at most, but it was still enough to cause 2.5m deviations at 60m

 

[Reliku]

Funny. That's a weird issue. Glad you found it! :tup: