FX Crown Tuning anomoly

[jps2486]

My Crown MK2 was originally set up as a .22 cal and shot well. I decided to convert it to .177 with a 600mm barrel. I de-tuned it by reducting the reg pressure from 155 to just under 100 because I wanted to shoot JSB 13.4 gr pellets at 20 fpe or 815 fps. I had the T/P set at .177/.22 and the hammer spring on Max. Ok, it was within my goal. For the heck of it, I started reducing the HS a step at a time till I got to No. 2. Guess what? The velocity INCREASED. Am I missing something?

 

[HogKiller]

One guess and because I'm not familiar with the MK2's HSA and I can't find it on the schematics, is there a screw that can rotate when you are turning it down? I've had this happen on my Maverick.

 

[Jlowe]

My Crown MKII did the same thing to me when I switched from .25cal 600mm to 22cal 500mm. I turned the Regulator down to 110 bar and there was almost no curve in the HS adjustment. Basically it shot almost the same from 1 to 23 with a little variance in the middle. I turned it back up to 150bar and got the full HS adjustment that I had on the 25cal. I also adjusted my gun's IHS when I got it to almost max internally, so maybe turning it down by taking the stock off might help. I don't know if you did that or not, but from the factory they do come set at a standard range, which may be why I can't get mine to shoot at a lower pressure.
Another words, I would say 100 bar is too low. Try increasing it and see what happens.

 

[ThomasT]

My Crown MK2 was originally set up as a .22 cal and shot well. I decided to convert it to .177 with a 600mm barrel. I de-tuned it by reducting the reg pressure from 155 to just under 100 because I wanted to shoot JSB 13.4 gr pellets at 20 fpe or 815 fps. I had the T/P set at .177/.22 and the hammer spring on Max. Ok, it was within my goal. For the heck of it, I started reducing the HS a step at a time till I got to No. 2. Guess what? The velocity INCREASED. Am I missing something?

Try viewing this video:

I reset mine after viewing this video.
ThomasT

 

[elh0102]

I'm not a tech, but I've played with enough tuning to appreciate the balance required between the HST and reg set point. My guess, at your low reg setting, the higher tension is keeping the valve open too long to maximize velocity. I find my maximum velocity at a given reg set point, and go from there. If your maximum velocity at this setting is more than about 110% of your goal, then back down the reg a little. At that point, the velocity should decrease with lower HST.

 

[18.13]

I've got my .25 cal shooting 60fpe with reg at 115b hammer spring on 12 maybe this helps

 

[Scotty1]

I’m guessing you’re over-driving your valve at that reg pressure. If you previously had it @155 bar, I’d imagine you have a hammer weight in there as well? Try turning the reg up a bit.

 

[jps2486]

I'm in the process of adjusting the hammer spring adjuster. I can't believe how out of whack this is from the factory. You would think they would have these parts pre-adjusted in an inspection tool before assembling.

 

[ThomasT]

I'm in the process of adjusting the hammer spring adjuster. I can't believe how out of whack this is from the factory. You would think they would have these parts pre-adjusted in an inspection tool before assembling.

Hello jps2486

Sounds like your HS was as bad out of adjustment as mine was . After all we should not expect too much from the factory, we only paid a couple of grand for the gun......

Boy it makes me want to jump up and down and say bad words.

ThomasT

 

[douger]

what kinda pre load are you using for the 22/177 can measure it let us know

 

[ThomasT]

what kinda pre load are you using for the 22/177 can measure it let us know

Hey @douger

I sent you a reply PM

ThomasT

 

[tor47]

I’m guessing you’re over-driving your valve at that reg pressure. If you previously had it @155 bar, I’d imagine you have a hammer weight in there as well? Try turning the reg up a bit.

Think he is right. What is probably happening is that when you lowered the pressure, the hammer on previous setting is hitting the valve harder because of less air pressure on the oposite side. The valve then bounce back faster from the valve spring, on the oposite side, and is closing faster than it normally would. Imagine if you throw a ball hard againts a wall, the harder you throw it, the faster it will bounce back at you. You can probably adjust the internal hammer adjuster until it doeas not touch the wheel on the lowest setting, and still have more tension than you need when turning the wheel upwards, when adjusting for .177.

 

[tor47]

I'm in the process of adjusting the hammer spring adjuster. I can't believe how out of whack this is from the factory. You would think they would have these parts pre-adjusted in an inspection tool before assembling.

Lowering the pressure from 155 bar to 100, is a big step. The previous hammer setting was probably fine for that high pressure. Also when you change from .22 to .177 means you can lower the hammer tension even more. Seems to me the gun was setup for high power in .22. Using 150bar or more is normally only nescesarry if you want to shoot heavy slugs. Now you change the gun to a low power setup (relative to what it was before, but still powerfull for a .177), which means you have to back off allot on the hammer spring tension.

 

[douger]

I'm in the process of adjusting the hammer spring adjuster. I can't believe how out of whack this is from the factory. You would think they would have these parts pre-adjusted in an inspection tool before assembling.

WHY WAS YOURS MAXED OUT, FROM OTHER CROWNS I HAD GREAT LUCK WITH LOT LESS HAMMER PRE LOAD 135 BAR MAX FOR A 380MM 22 CAL MINE SHOT 967 ON POWER 14 WITH A 16 GR AT 130 REG PRESURE FOR 5 MAGS

 

[jps2486]

I tuned the gun to the velocity that I wanted with a certain pellet, then when I DECREASED the hammer spring, velocity went up. I didn't think it would do that.

 

[Melo]

Rescato el tema, simplemente cambia el resorte del martillo por otro que tenga menos fuerza y podrás bajar aún más el regulador.