Tuning regulator questions....

[tsmith]

i have a .25 wildcat mk1. when i bought it it had the factory reg. when left overnight i needed to fire 3 shots to bring the fps to speed. i changed it out with a huma. same problem. what else can cause this?

problem #2. when i do a shot string over the chronograph, it stays whithin 25 fps from beginning to end BUT, it seems to have a slight bell curve. as if the reg is not consistent with reg pressure. it is not irratic, but different fps at 230 bar than it is at say 180 bar. i have the reg set at approx 135 bar.

any advice?

thank you.

 

[madeintheuk]

Maybe the reg is leaking past the seal in the tube? Maybe check for burrs in your tube, or damaged o rings. Maybe even that it’s seated properly. I’m no expert, but my huma wildcat mk2 reg is flawless, and if yours is new, I would guess something else is causing the issue. 

 

[elh0102]

Use some oil or soapy water and check for leaks. Your current tune might not be very well balanced. At the current reg set point, what is your maximum velocity with full hammer spring tension, and how does it relate to your desired velocity? In most rifles, you probably want to be around 97% or so of maximum, but rifles and regs vary. My Royale with Huma reg gives best consistency closer to full power, maybe 98%+. Your velocity should not vary in the manner you describe, and the ES should be smaller.

 

[nervoustrig]

#1 is the classic symptom of regulator creep. Solving the slow first shots is sometimes as simple as getting the hammer spring tension adjusted properly. Gradually increase the hammer spring tension until the velocity no longer increases, then back it off until the velocity falls to about 97% of that maximum. For example, if the max velocity is ~900fps, reduce the hammer spring tension until the velocity falls to 900 * 0.97 = 873fps. That will put the gun at a state of tune similar to an unregulated PCP operating near the top of its bell curve...meaning a varying pressure will have very little influence on the velocity.

If that doesn't remedy it, you will need to address the creep at its root cause. Creep is caused by surface defects in the regulator's valve seat. That causes the pressure to rise up most of the way but then a small amount of air will continue to weep through the surface imperfections over a period of minutes or hours until it finally rises high enough to totally squish the valve seat together and completely halt the flow of air. So the cure is to dress the valve seat smooth with an abrasive or replace it if that is an option. If it is a simple geometry, you can use fine wet/dry sandpaper to dress it to a smooth finish. If it is a tapered or convex seat, an abrasive compound (paste) can be used to burnish the mating surfaces together and bring them into an intimate fit.

Note, a leaking O-ring in the regulator will NOT cause this symptom. It's all about the valve seat.

#2 may be another symptom of sub-optimal hammer spring tension. A regulator's input regulation characteristics will produce a slightly higher output pressure when the input pressure is high. That makes the valve harder to knock open and can produce a slower velocity (speaking of the gun's main valve this time, not the regulator's valve). As the pressure begins to fall, the hammer can knock open the valve more easily and the velocity will rise. Then finally when the pressure falls low enough, the velocity will begin to drop. The result? A slight bell curve shape.

 

[2fast2furious]

Get a maverick or impact m3. It will fix the issue.

 

[TeOh1776]

Get a maverick or impact m3. It will fix the issue.

Hahahahhaha ^yes!

 

[tsmith]

Get a maverick or impact m3. It will fix the issue.

overkill for me. i tune a gun once for best shot count and respectable power combination and leave it. 

my wildcat with max hammerspring before it starts to go back down is 833 fps with jsb 34 gr. i have it set to 800 fps.

 

[elh0102]

Get a maverick or impact m3. It will fix the issue.

overkill for me. i tune a gun once for best shot count and respectable power combination and leave it. 

my wildcat with max hammerspring before it starts to go back down is 833 fps with jsb 34 gr. i have it set to 800 fps.

And that's app 96% of max. My guess, you have a reasonably well balanced tune. Of course the only thing that matters, you're hitting your target to your satisfaction. It's easy to get bogged down in theory, and miss the fun of shooting!

 

[tsmith]

Get a maverick or impact m3. It will fix the issue.

overkill for me. i tune a gun once for best shot count and respectable power combination and leave it. 

my wildcat with max hammerspring before it starts to go back down is 833 fps with jsb 34 gr. i have it set to 800 fps.

And that's app 96% of max. My guess, you have a reasonably well balanced tune. Of course the only thing that matters, you're hitting your target to your satisfaction. It's easy to get bogged down in theory, and miss the fun of shooting!

elh..

you are correct. and i am definately not one to nit pick. i dislike target shooting. i usually only shoot to hunt or pest. i have no complaints with my hit percentage. and when i miss, i blame myself or the pellet since i refuse to sort pellets. i use them all.

i just think it is strange how i have replaced the reg and it performs exactly the same with the huma as it did with the stock reg. no worries im not touching it.