FX Wildcat MK3 VP with a 300 bar bottle been having issues with consistency where it was varying almost 200 fps within a few shots. I got it to be consistent but now while trying to tune, the velocity changes depending how full the tank is. If the tank is at 300 bar down to about 220 bar it shoots at about 860fps on power wheel 3 but once it drops under 220 bar, the velocity goes up to 930. First reg is set to 160 and second reg is set to 120... I can only think that the velocity is going up as the tank pressure goes down because the valve is opening more due to not having to fight as much pressure from the reg and this only happens on the lower settings of the power wheel. Power wheel 5-7 stays the same velocity no matter what. Overall it is just weird because the regs should be preventing any of these changes coming from the bottle anyways. If it is the regs, which one would you suspect or maybe both?
FX Does your velocity change depending on full tank or less?
- Thread starter jskd82
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Check your rear gauge as you shoot. If its inconsistency is caused by regs, you will notice fluctuation on the gauge. ESPECIALLY that big of a speed difference.
I would look other places first, like possibly gamer adjuster gouging wheel (old mavericks and mk3 wildcats had this problem), or too light hammer for reg pressure which will give you a sort of bell curve when shooting like an unregulated gun.
I would look other places first, like possibly gamer adjuster gouging wheel (old mavericks and mk3 wildcats had this problem), or too light hammer for reg pressure which will give you a sort of bell curve when shooting like an unregulated gun.
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He stated the first reg is at 160 and the second is at 120.
I agree with @madeintheuk. Shoot a string from full to empty and make adjustments to your hammer once you clear the gauge off from being the problem.
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You already answered your own question. When your gun is set on 5-7 it’s tuned properly. When it’s set on 3, you’re on the downslope and it’s not tuned perfectly. Having two regs can hide some reckless tuning but there are still parameters. On the surface your “power wheel” may appear to be just a convenient speed controller. But it’s not. It’s just a fine tuner totally dependent of your reg setting.
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while I agree with you, there’s no reason to call it careless tuning. Without the proper know how, and lot of guys buying FX guns can become overwhelmed with all the adjustments without knowing exactly how they work in harmony. After all, that’s why this forum exhausts. To help those that are less knowledgeable about a subject.
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Sorry if I offended you. But I reckless tune my guns from time to time when I want to shoot something lighter or just slower. If you can think of a kinder more gentle term, I will try to use it moving forward.
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Point I was trying to make, is as a new comer reading your response, without knowing you from your posts like i do, you come across as coarse, and could be taken the wrong way by some. I’ve done this myself, and after posting something thought, wow, I sounded like an ass!
Sometimes it’s nicer to come in sounding more friendly, and less like you’re attacking the poor guy for maybe not knowing as much as you about tuning!
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Thanks for the replies, I replaced the stock gauge with a digital gauge and getting the same result. The digital gauge shows about 4 bar drop after each shot which recovers quickly when the tank is full but starts to take longer as the tank pressure drops. The stock hammer weight was 10.55g and was too light, it would not let me go above 90bar reg 2 pressure as it would lose velocity at that point. I am currently using the Huma tuning weight at 13.17g. I have also tried the 14.54g but that seems too much for what I'm trying to tune for. Essentially I want power wheel 7 to be able to shoot a 23 grain slug in the 900's and be able to dial down to shoot a JSB 18.13g at 850-890 fps. I have tried tuning with second reg from 100 to 125 bar at 5 bar increments with first reg at 150-160. I have also tried with the hammer spring adjusting screw backed off to 6mm and screwing it in 1/8 to 1/4 turn adjustments until I get some velocity drop off on the power wheel 7 setting and also some differentiation between the power wheel settings. I don't believe it's due to reckless tuning or whatever you want to call it, I take no offense. It happens at every adjustment I've tried to make as soon as the tank pressure drops. If it is as you're saying where the lower end of the power wheel isn't properly adjusted, what do you suggest to tune it? I have turned the adjustment screw in 2 full turns in from the 6mm setting and that gave me power wheel 7 shooting at 1021fps and power wheel 1 at 726fps but as soon as the tank pressure drops power wheel 1 will spike up to shooting 900+. This happens every time no matter what my settings has been. Thanks.
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BTW those speeds are all with the JSB 18.13 and I have FX sending me brass pistons for the regs to try. Another thing is there is a small leak from the barrel which is likely coming from the valve seat, which is also on order, not sure if that could cause this issue though?
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it’s normal for it to take longer to recover that huge plenum as pressure in the bottle drops, as long as it’s recovering. If it isn’t changing setting after the shot, and remains verily constant, I wouldn’t be blaming reg at all. This is either tuning problems, or as I said before, possibility of power wheel/hammer weight gouging causing inconsistencies in velocity.
What you’re explaining still seems to me (if reg is working properly) that the hammer is too light for the reg pressure you’re at.
What you’re explaining still seems to me (if reg is working properly) that the hammer is too light for the reg pressure you’re at.
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Well now, that’s information that could have been useful. If the valve seat or valve is damaged, or dirty, this could cause all sorts of wierd velocity issues. I would get it repaired properly before trying to tune and shoot
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You can’t have two solid tunes for two different projectiles that far apart in weight and drag. If you want to shoot both of those projectiles on the same reg setting, one tune is going to be jacked up. Sorry if jacked up is offensive. I would focus on the slug tune like you did. Pellets are more forgiving of a wonky tune. Hopefully wonky isn’t too harsh. You could probably get away with a pellet/slug tune on the same hammer wheel number if you switch your pellet to a 25gr MRD. But your gun might not like them as much as the faithful 18.1.
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Thanks, I don't believe the hammer is too light as it isn't losing velocity at the top end of the reg setting and I have gotten it to 1047fps with the adjustment screw backed out to 6mm at 125 bar on reg 2. The heavier 14.54g weight was too heavy because with the same settings my power wheel adjustments 1-7 all shot at the same velocities which means the hammer is hitting the valve and staying open too long. I'll try to change the valve seat and tune after that as you suggested.
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Lol I'm not offended by your choice of words, thanks for replying... I guess I am mainly tuning for 23 grain slug but was hoping to see the 18.13g fall in there somewhere at the lower power wheel setting between 850 and 900fps, which it does but only at the bottle pressure above 220bar, which still confuses me. I'll have to try the JSB 25.39 and see where they fall.
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Fill your gun all the way to whatever max fill you fill it to, then read your gage, shoot it till drops about 50bar in air pressure, and read it again. Proceed till you reach the about 10-15bar from your reg and see if your reg pressure had dropped substantially. I had that problem once, I had replace the o rings for the rear reg (mine is a mkii). And clean the reg housing area as well. But it fixed the issue of fps jumping around for high and low settings.
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Yes I notice the pressure drops about 5 bar between full tank 300 bar and lower 200 bar. Starts off at 120 bar and then only goes to 115ish once the tank pressure drops. I'll check on that and change it out, thanks!
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At a given reg set point, find your max velocity using the hammer settings and then back the hammer energy back 5% off that peak velocity. You'll be in a good place there. Shoot a string and see if you need to fine tune any.
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I decided it was time to retune my Panthera 600mm 177 for use in my yard during the winter. It has been tuned to shoot (on the knee) 20grain Zan slugs at 980fps and has been magical, but that’s too much juice for my yard. Before a proper retune, I decided to see what it could do running a jacked up/wonky tune. So I left the reg at 150bar and just dropped the power wheel setting until it was shooting 13grain Zans at 980fps. The ES was just as good as it was on the knee, so I proceeded with a 10 shot group at 58y. I hadn’t shot it for a few weeks and was really enjoying it so I extended the group to 20 shots. Here it is:
I think it’s pretty solid for a wonky tune and moreover, it’s really quiet and efficient. I fully expect it to suffer from a bit of speed loss resulting from creep but I’ll just find the necessary power wheel adjustments to compensate for the first couple shots. Anyway, while I agree that it’s optimal to be on the knee, it’s certainly possible to use the power wheel to adjust to different projectiles with no appreciable loss of accuracy. It’s just a matter of having a good regulator (or two). I’ll stick with my jacked up tune for now and I don’t think the rats will be any better off.
I think it’s pretty solid for a wonky tune and moreover, it’s really quiet and efficient. I fully expect it to suffer from a bit of speed loss resulting from creep but I’ll just find the necessary power wheel adjustments to compensate for the first couple shots. Anyway, while I agree that it’s optimal to be on the knee, it’s certainly possible to use the power wheel to adjust to different projectiles with no appreciable loss of accuracy. It’s just a matter of having a good regulator (or two). I’ll stick with my jacked up tune for now and I don’t think the rats will be any better off.
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