Impact hst wheel question

Do you have the added hammer weight?

Its likely that you will need to raise the pressure a bit some to make use of the last 2 settings, IMO. Likely driving the valve open far enough to hit plateau on that #4 setting...



Maybe try 150-160 bar if you want full use of that wheel, or remove the extra hammer weight...if you want more power then you currently have (980~ with 33.95) then go the higher pressure route, if you are content with the 980~ then remove the weight and see if you can still hit that at max hammer setting.

First, do you have a Huma digital gauge telling you that your reg is set at 140 bar, or are you just relying on what the reg gauge indicates?

...and are you shooting those JSB 34gr pellets out of a pellet liner or a slug liner?

Where is your hammer spring preload set? 

People measure different ways, what I'm really wanting to know is if you have adjusted the preload? Is it somewhere in the middle, 3/4 or is it near maximum? Sometimes if there isn't enough preload, you'll get to the maximum velocity on the power wheel setting on 4 or 5 and then it will decrease or stay the same when you turn the wheel to 5 or maximum. You might need to take the steps that Ackuric mentioned above but adjusting the preload so that the power wheel will barely turn when on maximum and adjusting it back from there may fix your problem. I have almost the exact same set up as you...My hammer spring preload is almost maxed and my regulator is a little higher at 145BAR, my valve adjuster up front is on 3.5 lines and my velocities with the 33.95 are about 1010fps. I shoot slugs with my Impact but use the 33.95's as my baseline...1010fps The difference is that when I turn down the power wheel from maximum, the velocities decrease and visa versa. If I'm understanding your question correctly, this is what you're trying to remedy? I'd start by increasing the preload and seeing if that helps. If you're already near or at maximum preload, take Ackuric's advice and bump the regulator to 145BAR-150BAR and see if that does it.

Stoti

Mark, with the plenum can it is common for the velocity to be the same on Max as it is on #5, and then less on the other settings. Here is something for you to try, but first make note of your current settings so you can go back to them afterwards if you want to. And to facilitate the procedures outlined below I recommend you remove the air gauge in the bottom of your plenum and install your Huma Digital Pressure Gauge.

Turn your valve pin spring tension adjustment nut all the way in, make a registration mark at the top or 12:00 position with a piece of tape or whiteout, then turn it out 5 full turns. Next set your Power Wheel on its Max setting. Then using a 1.5mm ball end Allen key turn the 3mm hammer spring adjustment screw (located in the hammer spring adjustment block) all the way in until the Power Wheel is locked in position and will not turn. Now back out that same 3mm screw a couple times...enough to free up your Power Wheel.

Now shoot your gun over your ProChrono DLX and note the velocity. Continue to turn that 3mm hammer spring tension adjustment screw out a little bit at a time and shoot over your chronograph to see the velocity. As you keep doing this you will see the velocity reach its highest point - or peak - as you turn the 3mm screw out farther and farther you will see the velocity drop lower and lower. So by turning the 3mm hstas back and forth we will eventually ascertain the highest velocity possible at the current regulator setting of 140 bar. 

From here you can turn the Power Wheel down to #5 and the velocity will probably be about the same as it was on Max, but will go down as you turn the Power Wheel to one of its lower settings. But back to the point, you have now found the highest possible velocity that can be achieved at this reg setting with this particular projectile, and if you want any higher velocity than this you will have to turn your regulator up higher. So now just for giggles lets turn that reg up to 150 bar and shoot over your chronograph and see what the velocity is now. (I would just leave your PW on #5 for this because your velocity on #5 will be about the same as it is on Max...but your extreme spread will be lower and your consistency will be better on #5 than it is on Max due to the can plenum you are using).

Now if your velocity is high enough by having turned the reg up to 150 bar so good and well...if not turn it up to 155 bar and see what velocity you get, and then 160 bar, etc. At some point spend some time playing with the valve pin spring adjustment nut ("VPN") by turning it in 1/4 turn at a time and shooting over your chronograph. You will discover that as you turn the VPN in more and more, your velocity will drop lower and lower.

This is important to know for several reasons... lets say you happen to know what the most accurate velocity for a particular projectile is, but the velocity on PW setting #4 is too high and the velocity on #3 is too low...so then you would set the PW to #4 and use the VPN to lower the velocity down to your desired setting. This method of setting a projectiles chosen velocity will also result in the best consistency, lowest extreme spread, and lowest standard deviation. 

If at some point you decide to turn your reg pressure down I personally recommend letting all the air out of your rifle before doing so. Even though it is supposedly okay to lower your reg pressure with the FX AMP regulator, I don't recommend it because doing so will abrade the teeny tiny o-rings on its adjustment screw and you will eventually get a leak there. (changing those little o-rings may cause you to smash furniture and things close at hand)  And if you have installed a Huma Gen 3 regulator in your Impact MKII then never ever turn the reg pressure lower while the gun is under pressure! Doing so will ruin the tiny white delrin chip contained inside and the chip will have to be turned over on its other side or be replaced in order to restore the reg's proper function.

I was able to shoot the JSB 34 grainers into one hole groups at 1030 ft/s for 80 ft lbs energy out of my .25 cal. slug liner at 50 yards. It would be interesting though to see how fast the FX Hybrid .25's would shoot out of your slug liner accurately...you could get them screaming out of your rifle pretty darn fast, especially when you consider that they only weigh 26 grains and will go about 100 ft/s faster than the JSB 34's will. I imagine that at about 1100 to 1115 ft/s they would be considered Iguana Grenades! The speed of sound at sea level here is about 1130 ft/s...so exceeding that will cause your rifle to make quite a bang indeed! 

All the best, Chuck in Paradise 

I have tried shooting jsb 34 gr at 960 fps for a while then went back to 900 

it seems for me they can not handle more fps beyond 920 cause of their design 

they will shoot at higher fps very well on close distance but once u try shooting 80 yards and beyond they loose stability 

that's what I have noticed