FX Tuning question for the group

[Patrick1]

I have noticed that average pellet speeds have dropped slightly over a shooting session, with each successive magazine. Average speed dropped from 887fps to 872 fps.
Also, an occasional very slow(20-25fps from average)pellet speed has sometimes occurred but this is not a “regular” occurrence! The gun is a .22 Maverick compact shooting unlubed 15.9 FX pellets.

Any thoughts on what might cause this phenomenon? For context, I recently replaced the second(latest iteration)AMP reg and the breech seal, both lubed well.

Any thoughts from the group could help my tuning/maintenance would be appreciated!

 

[Firewalker]

What are your reg settings?

If I only have a 25 bar difference between the regulators, it takes longer and longer for the front to fully fill. This is the benefit of a Sekmet gauge, I can see when it's full for the next shot.

I have a 50 bar difference now for my .30 setup and I can shoot back to back until I hit reg pressure on my bottle before it falls.

 

[nervoustrig]

x2 on Firewalker’s advice.

Also may want to try backing off the hammer spring tension ever so slightly. This behavior is representative of the fact a regulator’s output pressure will trend downward a little as the reservoir pressure falls. If the HST is set too strong (i.e. close to the velocity plateau), the velocity will rise and fall with the reservoir. Backing off the HST a little will usually help flatten it out.

 

[Firewalker]

x2 on Firewalker’s advice.

Also may want to try backing off the hammer spring tension ever so slightly. This behavior is representative of the fact a regulator’s output pressure will trend downward a little as the reservoir pressure falls. If the HST is set too strong (i.e. close to the velocity plateau), the velocity will rise and fall with the reservoir. Backing off the HST a little will usually help flatten it out.

Nice!

 

[Patrick1]

Thanks for the reply! You are always helpful!! I am running front reg at 120 and second reg at 81-82. The second response is probably gonna be the one, cuz I have noticed very small changes in the internal hs can change consistency quite a bit. The explanation is very helpful!

 

[Patrick1]

Update! The “backing off the hammer” seems to have fixed the slow reduction of speed I saw. Slight speed reduction was observed due to the hammer adjustment. Only about a 6 fps avg speed reduction over all six mags. Thanks to Nervoustrig!

However,I still am seeing an occasional blip with a very slow speed. I have also replaced the hammer with a new one( from Pantera) which should fix the wear/gouging done by the sear-this has been an ongoing issue with FX. This had led to occasional slow speeds in the past per Utah Airguns.

Any ideas on why this happens?

 

[HogKiller]

Update! The “backing off the hammer” seems to have fixed the slow reduction of speed I saw. Slight speed reduction was observed due to the hammer adjustment. Only about a 6 fps avg speed reduction over all six mags. Thanks to Nervoustrig!

However,I still am seeing an occasional blip with a very slow speed. I have also replaced the hammer with a new one( from Pantera) which should fix the wear/gouging done by the sear-this has been an ongoing issue with FX. This had led to occasional slow speeds in the past per Utah Airguns.

Any ideas on why this happens?

You aren't accidentally firing the gun with the cocking handle back are you?

You may wish to lube the hammer and spring, with some real lube not Silicon oil, just a light coat, I use Mobile 1 or Try-Flow both will last a LONG time. Your pressure differentials are good so that's not the issue. I've got two Mav's. key is to get that Hammer Macro dialed in, max speed then back it off a touch, Back to the gouged hammer, if you pop it apart, look inside and make sure nothing is broken off, there is a thin section between the hammer and ...don't remember but it's thin and can break, a piece may be floating around in there.

 

[Patrick1]

Nope! I don’t fire the gun with the cocking handle back. The hammer wear issue is known to FX according to Utah Airguns and they sent the “new” Pantera hammer as a fix cuz it is a bit harder than the originals. I use a very light coat of a moly grease on the hammer and hammer weight. According to Utah, one of the issues seen by users is an occasional low shot speed caused by ‘nicks’ in the hammer caused by the sear being made of a harder metal than the hammer.

 

[ocdairgunner]

Nope! I don’t fire the gun with the cocking handle back. The hammer wear issue is known to FX according to Utah Airguns and they sent the “new” Pantera hammer as a fix cuz it is a bit harder than the originals. I use a very light coat of a moly grease on the hammer and hammer weight. According to Utah, one of the issues seen by users is an occasional low shot speed caused by ‘nicks’ in the hammer caused by the sear being made of a harder metal than the hammer.

I bought a used Wildcat MK3 in .30 cal. It exhibit a similar pattern. I would fill the bottle to 250 bar and shoot it down to 120 (second reg set to this) and somewhere around the middle of my shooting string I had 3-4 shots that were 25-30 fps lower than the average.

 

[Patrick1]

I bought a used Wildcat MK3 in .30 cal. It exhibit a similar pattern. I would fill the bottle to 250 bar and shoot it down to 120 (second reg set to this) and somewhere around the middle of my shooting string I had 3-4 shots that were 25-30 fps lower than the average.

It was a random thing that happened with shots cuz of the hammer “spinning” in the gun(per Utah tech). If you examine the hammer where the sear grabs it, you may find little “nicks” or gouges on the surface. I looked at it with a magnifying glass and saw hundreds of the little gouges where it should normally be smooth.

 

[ocdairgunner]

It was a random thing that happened with shots cuz of the hammer “spinning” in the gun(per Utah tech). If you examine the hammer where the sear grabs it, you may find little “nicks” or gouges on the surface. I looked at it with a magnifying glass and saw hundreds of the little gouges where it should normally be smooth.

I will have to take a closer look. I took out the hammer and spring last weekend to clean up everything. It cant hurt to take a second look and lube it properly.

 

[Trucker3573]

Update! The “backing off the hammer” seems to have fixed the slow reduction of speed I saw. Slight speed reduction was observed due to the hammer adjustment. Only about a 6 fps avg speed reduction over all six mags. Thanks to Nervoustrig!

However,I still am seeing an occasional blip with a very slow speed. I have also replaced the hammer with a new one( from Pantera) which should fix the wear/gouging done by the sear-this has been an ongoing issue with FX. This had led to occasional slow speeds in the past per Utah Airguns.

Any ideas on why this happens?

I had occasional very slow speed shots on mine and I realigned the pellet probe and they disappeared. Take off the cheek piece and look in the hole to access the probe screw. That screw should be positioned front of center. Mine had moved slightly to being centered in the hole.

 

[Patrick1]

Great suggestion! Yeah, looked at the “timing” issue with the probe and maybe should play with it more. Mine is set forward of center with the front edge of the circle just touching the front of the opening. Maybe the linkage is loose, but I “locktited” the 2 grub screws before.
The question may be -“how much front of center”! Or, exactly “where” front of center!

 

[Patrick1]

I will have to take a closer look. I took out the hammer and spring last weekend to clean up everything. It cant hurt to take a second look and lube it properly.

I will have to take a closer look. I took out the hammer and spring last weekend to clean up everything. It cant hurt to take a second look and lube it properly.

By the way, you can’t really polish these nicks away easily. I tried with my Dremel with only small improvement. The new Pantera hammer may be the way to go.

I may have some of that OCD stuff in me, too! Let me know how it turns out!

 

[ocdairgunner]

I had occasional very slow speed shots on mine and I realigned the pellet probe and they disappeared. Take off the cheek piece and look in the hole to access the probe screw. That screw should be positioned front of center. Mine had moved slightly to being centered in the hole.

I did that and it has certainly helped!

 

[ocdairgunner]

Great suggestion! Yeah, looked at the “timing” issue with the probe and maybe should play with it more. Mine is set forward of center with the front edge of the circle just touching the front of the opening. Maybe the linkage is loose, but I “locktited” the 2 grub screws before.
The question may be -“how much front of center”! Or, exactly “where” front of center!

I used the following video for timing. Again it does not go into too much detail about how forward it should be. But I followed it pretty closely and it took care of my timing issues/fps drop from my initial tests.

 

[Patrick1]

I used the following video for timing. Again it does not go into too much detail about how forward it should be. But I followed it pretty closely and it took care of my timing issues/fps drop from my initial tests.

Me, too! One other issue to consider is the hammer spring adjuster screw- the one that attaches the wheel to the gun body. It has periodically loosened which can cause some shots to be much slower. Happened to me several times.