FX Wildcat MK3 BT Random FPS Drop in Shot String (Update Post #16- 4/12/24)

[ocdairgunner]

ODC what did you end up finding out on this? Mine is doing the same thing except dropping from 900 fps to about 700 for a few shots?

@Trampus99

It turned out to be a combination of properly aligning the probe and dialing in the right tune. That not only eliminated the random FPS drops but also resolved the low FPS issue on the first shot after the gun had sat for several hours or overnight.

In my case, after correcting the probe alignment and timing based on the video in post #13, I focused on refining my tune. Since I'm shooting .30 cal, the most critical factors were ensuring the hammer weight was correct (12 grams), the hammer was polished, and that hammer spring (HS) tuning was carefully balanced with the second regulator.

Currently, my second reg is set at 120 bar and the first at 145 bar. This setup allows the 600mm barrel to push 44.75gr JSBs at 895 FPS. My tuning process was as follows:

1. Set both regulators to the values above.
2. Turn the power wheel to 7.
3. Turn the HS screw all the way in.
4. Slowly back the HS screw out (counterclockwise) until velocity stopped increasing — in my case, this was around 915–920 FPS.
5. Then I turned the HS screw clockwise in small increments until I settled at 895 FPS.

Once satisfied, I filled the bottle to 250 bar and shot 4 mags (52 pellets) to record a full string. The extreme spread was just 9 FPS with no erratic drops like before.

To test the cold shot issue, I let the gun sit overnight, then chrono'd the first shot the next day. It clocked in at 893 FPS — right on target. I fired another 30 shots and recorded a 6 FPS extreme spread. I've repeated this test multiple times after letting the gun sit for a day or more, and the consistency has been spot-on every time — no more erratic low first shots.

I hope this helps you resolve your issue as well. I was concerned that the regulator might need to be rebuilt but so far everything is holding up well.

 

[Matt7467]

@Trampus99

It turned out to be a combination of properly aligning the probe and dialing in the right tune. That not only eliminated the random FPS drops but also resolved the low FPS issue on the first shot after the gun had sat for several hours or overnight.

In my case, after correcting the probe alignment and timing based on the video in post #13, I focused on refining my tune. Since I'm shooting .30 cal, the most critical factors were ensuring the hammer weight was correct (12 grams), the hammer was polished, and that hammer spring (HS) tuning was carefully balanced with the second regulator.

Currently, my second reg is set at 120 bar and the first at 145 bar. This setup allows the 600mm barrel to push 44.75gr JSBs at 895 FPS. My tuning process was as follows:

1. Set both regulators to the values above.
2. Turn the power wheel to 7.
3. Turn the HS screw all the way in.
4. Slowly back the HS screw out (counterclockwise) until velocity stopped increasing — in my case, this was around 915–920 FPS.
5. Then I turned the HS screw clockwise in small increments until I settled at 895 FPS.

Once satisfied, I filled the bottle to 250 bar and shot 4 mags (52 pellets) to record a full string. The extreme spread was just 9 FPS with no erratic drops like before.

To test the cold shot issue, I let the gun sit overnight, then chrono'd the first shot the next day. It clocked in at 893 FPS — right on target. I fired another 30 shots and recorded a 6 FPS extreme spread. I've repeated this test multiple times after letting the gun sit for a day or more, and the consistency has been spot-on every time — no more erratic low first shots.

I hope this helps you resolve your issue as well. I was concerned that the regulator might need to be rebuilt but so far everything is holding up well.

I'm going to try adjust the timing on mine again and see if it changes. I attempted this months ago and thought it was all set correctly, but nothing changed in the shot string. Maybe I wasn't holding it far enough forward when tightening it back down?? No idea. While I am for the most part mechanically inclined, I'm also new to tinkering with airguns.

 

[Trampus99]

Thanks OCDAirgunner!!!!!

 

[Trucker3573]

@Trampus99

It turned out to be a combination of properly aligning the probe and dialing in the right tune. That not only eliminated the random FPS drops but also resolved the low FPS issue on the first shot after the gun had sat for several hours or overnight.

In my case, after correcting the probe alignment and timing based on the video in post #13, I focused on refining my tune. Since I'm shooting .30 cal, the most critical factors were ensuring the hammer weight was correct (12 grams), the hammer was polished, and that hammer spring (HS) tuning was carefully balanced with the second regulator.

Currently, my second reg is set at 120 bar and the first at 145 bar. This setup allows the 600mm barrel to push 44.75gr JSBs at 895 FPS. My tuning process was as follows:

1. Set both regulators to the values above.
2. Turn the power wheel to 7.
3. Turn the HS screw all the way in.
4. Slowly back the HS screw out (counterclockwise) until velocity stopped increasing — in my case, this was around 915–920 FPS.
5. Then I turned the HS screw clockwise in small increments until I settled at 895 FPS.

Once satisfied, I filled the bottle to 250 bar and shot 4 mags (52 pellets) to record a full string. The extreme spread was just 9 FPS with no erratic drops like before.

To test the cold shot issue, I let the gun sit overnight, then chrono'd the first shot the next day. It clocked in at 893 FPS — right on target. I fired another 30 shots and recorded a 6 FPS extreme spread. I've repeated this test multiple times after letting the gun sit for a day or more, and the consistency has been spot-on every time — no more erratic low first shots.

I hope this helps you resolve your issue as well. I was concerned that the regulator might need to be rebuilt but so far everything is holding up well.

Sounds about right where I am. My second reg runs 115-117 and I get right about 900 with 44.75 and 870 with 50 gr. Very good spreads. I get a bit of fluctuation on first shot after sitting but it’s within 10-12 fps tolerable for now anyway. I have a digital gauge on it and the reg always goes to 122-123 bar after sitting. I’ve personally never owned an amp reg that didn’t do this other than maybe when it was brand new, like never had a shot fired through it. lol. 5 minutes later it has the 5-8 bar creep.

 

[ocdairgunner]

I'm going to try adjust the timing on mine again and see if it changes. I attempted this months ago and thought it was all set correctly, but nothing changed in the shot string. Maybe I wasn't holding it far enough forward when tightening it back down?? No idea. While I am for the most part mechanically inclined, I'm also new to tinkering with airguns.

Yes, give it another shot and make sure it is set forward. Use blue Loctite on the grub screws because they will become loose and slip otherwise. Good luck!

 

[ocdairgunner]

Sounds about right where I am. My second reg runs 115-117 and I get right about 900 with 44.75 and 870 with 50 gr. Very good spreads. I get a bit of fluctuation on first shot after sitting but it’s within 10-12 fps tolerable for now anyway. I have a digital gauge on it and the reg always goes to 122-123 bar after sitting. I’ve personally never owned an amp reg that didn’t do this other than maybe when it was brand new, like never had a shot fired through it. lol. 5 minutes later it has the 5-8 bar creep.

Mine creeps up 2-3 bars as well. However, for some reason, the first shot is not slow anymore. It was an issue for quite a while but the last time I tuned this gun a couple of months ago, it somehow got rid of the slow first shot. I am taking a guess here but I think the HS and regulator has hit a balance. Even when the reg creeps up a couple of bars, the HS tuning and hammer strike is in such a balance that it over comes the higher reg and still gets me the first shot FPS that I am expecting. But that is just a guess at this point and nothing scientific.