Tuning FX IMPACT by the Reverse Way

It should be quieter and waist less air because the air valve is being restricted in how far and how long it stays open with the knob. This is not a right or a wrong way of tuning. I've seen videos where the long range shooting folks tune their Impact's the exact same way with great results. They pick the reg pressure and target velocity they want to have, then they use the valve control knob to slowly shut down the air until they have the tightest group.

The only right way is the one the target shows, if you gun is accurate to you, then is the right way !!

As you describe is good, I tune like that one of my impacts, and is really really accurate. (meaning in bench 25y I made 245-250 in practice, and in last official event 248) 25y is a millimetric game.

The problem is your relying on the bounce off of the rubber ball for consistency. Not a good idea IMO.

I find no need for valve stop, causes more problems in the long run than it's worth.

I'm with edosan... the target tells the tale. Doesn't matter how you get there as long as you get there.

You guys have more patience & know how then me. I simply Use near, apex & far zero. Punch it into ChairGun & count my shots, watch gauge and group. I need to buy another chronograph. 
The reg thing. I avoided them until I saw what consistency really is. Now I want a step down in-line reg for all my non regulated guns or just choose to shoot at higher power without a reg in play.

If the reg pressure is too high for the speed you want you "hit" eveything harder

My method is to set the reg and when the gun comes out, the speed increase about 10-15 fps 

My method is to set the reg and when the gun comes out, the speed increase about 10-15 fps

Click to expand...

Umm what ???

I personally would not stop at 910 fps in your case. But rather slowing it down to maybe 850 with 10-15 fps intervals. If the gun turned out to be more accurate at say 880-860, I might leave it there. If I absolutely then wanted to shoot at around 910, I might increase regpressure 5 bars, and repeat the same prosedure, and hopefully with next attempt have the same or better accuracy closer to desired speed. If I then not succeded, I would repeat same prosedure with another 5 bar regpressure increase. I might also start shooting groups at 930-920 fps (in your case) to make sure I also tested the accuraccy a lilte higher than 910fps. I would believe in your case it probably is not unlikely you will find a speed a litle lower (or maybe higher if you tested from 930-920) at the first attempts which may be more accurate then the desired speed. You will probably find the best accuracy at the desired speed by doing several attempts with a wider range of regpressure. It depends on the patience you have, I personally would probably stop at the speed anyware from 930-850 which gave the best accuracy, and be happy with it.

Thanks to edosan & Airgun-hobbyist!

Generally speaking, we will set the reg & hammer spring higher than the target velocity around 20~30fps

I wonder that anyone turn the reg & hammer spring really higher than the target speed (50 fps or more).

Then reduce the speed just by valve control knob. What it will happen?

Click to expand...

I personally doeas not like to reduce the speed to much like 50-100fps with valve knob only. I do not know if it hurt the gun (smash the ruberball to peaces?) on an extended period of time, so I try to avoid it just in case. I use the valve knob to reduce maybe 10-30 fps max, from hammer setpoint, to be on the safe side. If you first have redused the speed like 50-100 fps with hammer force, and then use the valveknob to reduse 10 fps more, the pellet speed might be more stable when shooting over a chrony.

My method is to set the reg and when the gun comes out, the speed increase about 10-15 fps

Click to expand...

Umm what ???

Click to expand...

I want for example 900 fps, so i set the reg to get 920 fps, decrease the hst to get 900 fps

More shots, less strike at the valve, less curve out of reg

The power comes from the reg and the fine tuning from valve ant hst

tor47. I believe you are correct.

Too much pressure one the valve hammer will reduce the life of C3 bumper. And the valve control knob also.

It's not a good idea.

Click to expand...

Every Impact owner should switch their C3 bumper to a delrin washer. It gives better performance and doesn't wear out like the worthless urethane oring that FX uses.

If I shoot on low velocity with the .177 barrel, I might have to drop up to 100fps with valve adjuster only, as I can take out all the slack on powerwheel, and the gun will still shoot 880-890 fps with lowest regpressure. So the impact might be a litle to powerful to tune down with regpressure and hammerspring tension only, on the small caliber. But when I use the .25 barrel, I can usually do the main adjustements with hammer and reg, before using the valve adjuster at all. I use the original C3 bumper, as the gun still shoots fine. I do not know if it is true, but the gun might shoot even hotter with a harder delrin washer, as it will not cushion the hammer strike as much as the original one? So maybe not a good idea if you shoot on low power on smaller calibers?

I have my .30 Impact maxed out for power and I shot well over 7,000 rounds before the C3 bumper deformed. Granted, it should not have failed at all, but that is the number of shots I got out of it before it failed.

Click to expand...

Some are failing well under 1000 shots. The pieces that come off of it can cause problems getting into things. It's good to have the delrin washer on hand when the other fails.

Thanks to edosan & Airgun-hobbyist!

Generally speaking, we will set the reg & hammer spring higher than the target velocity around 20~30fps

I wonder that anyone turn the reg & hammer spring really higher than the target speed (50 fps or more).

Then reduce the speed just by valve control knob. What it will happen?

Click to expand...

One of my Impacts shoots at minimum everything the jsb 18.2 @ 960 fps (transfer ports are bigger than stock and VS too) , so the only way to put it in 900 range is with the ValveKnob ... and to my surprise deadly accurate! 248 @ 25y (in an official benchrest event) is extremely accurate, that is basically 25 shoots in a hole the size of about 6-7mm

Fx should start selling them with delrin washers,from factory.Sad story I buy an impact and start swopping out c3bumper....cuz it crap..