.177" STX barrel kit

I would not open the brass transfer port before shooting it over a chrony. The reason I say that is because mine did not shoot slower than 880 fps with JSB exact 10 grains, with around 80-90 bar. That was with the power wheel taken all slack off the spring tension. Max speed was around 890 -900 fps before it started to waste air at that reg pressure. If I wanted to shoot slower I had to use the valve adjuster. All depending on what pellets, and power level you are gonna shoot at, there is no reason to make it shoot even faster in .177 caliber. Remember the impact is designed to shoot every caliber up to .30, and might already have a slightly heavy hammer, or spring for .177. So making it shoot even faster by widen the transfer port hole, may mean you have to use the valve adjuster to slow it down again. There is no more hammer spring tension to lower, when the wheel does not engage at all. So the standard opening on the transfer port is a good thing to have, in that caliber.

I got the .177 kit when I bought my .25 Impact a bit over a year ago. I had the .25 heavies shooting MOA groups at 100 yards at around 830fps reg set @ 140bar hammer spring dial at 4 or 5 I was definitely impressed by the gun. Installed the .177 kit and other than that the only adjustment I made to the gun was to turn the power dial down to one. I then shot a five shot group that wound up a single hole at fifty yards. Not only that but it shot that group within 3/4 inch of the POI of the .25 pellets I had just been shooting. I ran it over the chrony and it said 920fps. I think I was shooting the JSB heavies at 10.34gr. So, I would agree that it likely does not need a whole lot of anything in the way of mods to shoot the .177 fast enough or accurate enough to satisfy.

I made many mods to my gun since that time and would have to undo some of them to be able to shoot from the .177 barrel again. FX has it together with all of the adjustments and caliber changes available. When we modify things we upset that fine balance and loose some of the adjustability originally afforded us by them. I am just lately beginning to understand and appreciate this.