Sudden drop in feet per second...!?

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kmd1984

Member
Feb 20, 2016
997
14
Utah, United States
Hi,

My FX Bobcat Mk2 in .25 used to shoot the JSB Exact Kings at 860 on max, 620 on mid and 465 on low power, and the JSB Exact King Heavies Mk2 at 760/530/370.

Suddenly, for no apparent reason, my FPS dropped to 750/580 and 440 (JSB Exact King) and 640/490 and 360 with the JSB Exact King Heavies Mk2!? 

I did not change anything, so I have no idea what caused this...

Any ideas???

I would like to poing out that my FX Bobcat Mk2 used to shoot the Air Arms Diabolo Field 25.4 Grains, Domed pellets at 930 fps/full power, and 650 fps/low power. I then sent the gun to FX Airguns USA for a 'service'. While it was there, I asked Ernest to give me a little more shot count, and he did. He also installed a 3-way power switch, instead of the 2-way one. That is why I have three power settings. : )

On the "score card", when testing the gun, he wrote 900 fps with the JSB Exact Kings. Funny enough, when I got the gun back, I was only able to clock the pellets at 860??? Could it have something to do with me being at 2200 meters? Could that be the reason he was getting 900 fps and I only got 860???

Anyhow. That was then. Now my max power setting dropped by 100 fps overnight...

Why?



Thanks,

Kmd




 
Take it apart, have a look. Can probably break it down pretty easily with 3 or 4 metric hex keys and maybe a 10 and 14mm wrench.

Click to expand...


Take it apart and have a look? I don't think so.

A. I don't know how, but I am sure I can figure out how to take it apart. However, I would still not know what to look for. : )

B. I just paid FX to do that. So the last thing I am going to do, is to take it apart myself.

C. Considering that I just got the gun back and they did not really do a great job (that is a different story altogether), I would think that whatever happened must have something to do with them working on it last. Now, I don't know that for sure, but it is a legit [educated] guess.

Thanks,

Kmd
 
Upvote 0
Take it apart, have a look. Can probably break it down pretty easily with 3 or 4 metric hex keys and maybe a 10 and 14mm wrench.

Click to expand...


Take it apart and have a look? I don't think so.

A. I don't know how, but I am sure I can figure out how to take it apart. However, I would still not know what to look for. : )

B. I just paid FX to do that. So the last thing I am going to do, is to take it apart myself.

C. Considering that I just got the gun back and they did not really do a great job (that is a different story altogether), I would think that whatever happened must have something to do with them working on it last. Now, I don't know that for sure, but it is a legit [educated] guess.

Thanks,

Kmd
Click to expand...


Yeah fair enough, I didn't realize you just got it back from FX. I bet Matt means like lay a tissue or something over the pellet probe and take a shot and see if it flaps up from breech o-ring.




 
Upvote 0
Yes check the power switch area and breech / probe area for blow by, if present an o-ring may need replacing. Not an uncommon cause for major fps losses such as you are experiencing. If there is no blow by present anywhere in these areas then I'd be stumped and send it to someone experienced.



Also I'd note to yourself if the cocking lever feels the same roughly, in terms of distance until sear engagement and effort to get it there...if distance feels much shorter than normal or the effort is much less than it could be hammer travel / spring issue. Less likely cause but plausible.
 
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Since you mention you recently got it back after paying to have it serviced (BTW What was wrong with the gun to make you send it for service anyway?) I would speculate that you may have a regulator issue which believe it or not FXs are known to have sooner or later and would contact Earnest to let him now what is happening now before trying to fix it yourself. If you have to send it back then I would recommend having him install a HUMA even if you have to pay extra for it.

CA
 
Upvote 0
Take it apart, have a look. Can probably break it down pretty easily with 3 or 4 metric hex keys and maybe a 10 and 14mm wrench.

Click to expand...


Take it apart and have a look? I don't think so.

A. I don't know how, but I am sure I can figure out how to take it apart. However, I would still not know what to look for. : )

B. I just paid FX to do that. So the last thing I am going to do, is to take it apart myself.

C. Considering that I just got the gun back and they did not really do a great job (that is a different story altogether), I would think that whatever happened must have something to do with them working on it last. Now, I don't know that for sure, but it is a legit [educated] guess.

Thanks,

Kmd
Click to expand...


Yeah fair enough, I didn't realize you just got it back from FX. I bet Matt means like lay a tissue or something over the pellet probe and take a shot and see if it flaps up from breech o-ring.



Click to expand...


Roger that... thanks.
 
Upvote 0
Yes check the power switch area and breech / probe area for blow by, if present an o-ring may need replacing. Not an uncommon cause for major fps losses such as you are experiencing. If there is no blow by present anywhere in these areas then I'd be stumped and send it to someone experienced.



Also I'd note to yourself if the cocking lever feels the same roughly, in terms of distance until sear engagement and effort to get it there...if distance feels much shorter than normal or the effort is much less than it could be hammer travel / spring issue. Less likely cause but plausible.
Click to expand...


I will look into that. Thanks for the input.

Kmd
 
Upvote 0
Since you mention you recently got it back after paying to have it serviced (BTW What was wrong with the gun to make you send it for service anyway?) I would speculate that you may have a regulator issue which believe it or not FXs are known to have sooner or later and would contact Earnest to let him now what is happening now before trying to fix it yourself. If you have to send it back then I would recommend having him install a HUMA even if you have to pay extra for it.

CA
Click to expand...


My gun used to be a super mega hardcore tack driver. Never had an issue with it. Now, without wanting to get into details here, the gun hit the ground twice. After that it was never the same. It would have a POI change to the right, when going from full to low power and it started to have less shots per fill. And the pressure gauge was screwed up... So I sent it in. It needed a service anyway. You know. New seals and stuff like that.

Having said that. I almost ordered a HUMA regulator so Ernest can install it while he services the gun!!! But I could not find one [HUMA] in the US. Since I did not want to wait for one to arrive from Europe, I let it go. However, I am still thinking about getting one though... : )

Thanks,

Kmd
 
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So... I just cut a tissue to the same size as the thickness of a magazine and put it where normally the mag goes. When I shoot, it definitely moves a little bit. Hard to tell though it if is air that moves it or simply the "recoil"!? I can take the gun to my local gun shop and have them a look... If they tell me that it is a leak in and around that area. I will contact Ernest and see what he says.

Thanks,

Kmd



EDIT: What about putting soapy water around the breech area? That should show you if air is coming out of that area or not...
 
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It would have to be a puff large enough to feel by hand IMO to drop your fps by what you're seeing. Basically enough to put out a small flame from a lighter/candle.



If you have a pressure gauge on the rifle that shows regulated pressure then you can confirm that its set where it should be unless both the gauge and the regulator are equally off which is unlikely.
 
Upvote 0
It would have to be a puff large enough to feel by hand IMO to drop your fps by what you're seeing. Basically enough to put out a small flame from a lighter/candle.



If you have a pressure gauge on the rifle that shows regulated pressure then you can confirm that its set where it should be unless both the gauge and the regulator are equally off which is unlikely.
Click to expand...


The puff is for sure not strong enough to be felt by hand. I mean, the tissue barely moves...

I am not sure what you mean in regards to the reg pressure gauge!?

Thanks,

Kmd
 
Upvote 0
They do make one for the bobcat, got mine yesterday. Same as the Royale one. (Factory one in bag)

1542981124_14629866245bf806042abae3.43528086_20181123_055158.jpg


https://www.airgunsource.ca/en/huma-air-fx-royale-regulator.html

One here up in Canada, closer than Europe anyways.
 
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