JSB 18.1 FPS with Impact .22 ?

Wow, that's a lot more like what I was reading. I think Matt said he was running just over 900 at a setting of 1. 

Thanks,
Rusty

Thanks for the additional data points. I just did some more testing, and I can't seem to make it to 900 fps. 

Regulator as received reads 130 bar. Power wheel is on max, and I previously verified that the velocity adjusts with the wheel. Valve is as shown in the manual with two long and two short lines. JSB 18.13 gr velocity is 880 fps. The manual says the valve position is mid-range, but turning it out doesn't increase the velocity at all. Turning it in drastically reduces velocity, down to 223 fps avg at the min setting. 

I adjusted the reg to 140, valve as received at two long two short, and wheel to max, but it only went up to 892 fps avg. Increasing to 150 bar actually dropped the average to 886 fps, and still the valve doesn't increase if I turn it out. I even weighed the pellets just in case, and they're really 18gr like they're supposed to be. 

I set everything back to where it was when received, and called AOA, but after holding a while, it went to VM and I left a message. I'll see what they have to say tomorrow, but it sure sounds underpowered compared to all the other reports I've read. 

One other test I did was to shoot the gun down to below the regulator, and then looked at both gauges. I would think they would read the same when the tank pressure is below the regulator pressure, but that isn't the case. The tank gauge reads about 25-30 bar higher than the regulator. Of course it's no secret these aren't precision instruments

Thanks,
Rusty

Thanks for the link! I looked through it, and can't see anything that appears incorrect. The only check I didn't confirm was the hammerseat length because I was hesitant to unscrew the assembly.

I talked to AOA today, and they seem to agree that mine isn't up to the power it could be. They suggested that I try some other power settings, but beyond that, I'll have to send it in to let them take a look. If I want more than 880 fps from an 18.1 gr pellet, I fear that's what I'll have to do.

For those playing along, here are the results of today's testing. Note that these are a single shot at each setting, not averaged, so there are some variations that don't quite match what you'd expect. Bottom line is that it seems low on power. 



Cheers,
Rusty

Thanks for the suggestion. I thought about air leaking past the probe as a possible cause, but I never could feel anything. Sadly, the Impact is packed and departing tomorrow to let the AOA service dept take a look. I'll give it another try when it returns. 

Cheers,
Rusty

Greetings,

Just a follow-up to say that AOA seems to have corrected my low power issue. I was getting around 880 fps on max with the 18.1 JSBs before sending it to them, and now it's 960 fps. I wish they had made some notes about what they did, but aside from mentioning that the regulator was set to 141 bar, there weren't any details. Hopefully this will give me a little better performance out to 100 yds.

Cheers,
Rusty

I didn't specifically check the valve stem, but I did unscrew the valve adjustment maybe 3/16" out from the default position with no change in speed. The manual seems misleading when it says- "The default setting is near the center with 2 long lines and 2 short lines showing." I think this is probably max power, not what I'd call near the center. Screwing it in from that position had an immediate effect on the speed, and I was able to screw it all the way in to the first line, so I don't think it was the valve stem unless I'm misunderstanding how this works. 

Thanks,
Rusty