:)

Very interesting. Shouldn't the reg refill itself when the pressure is leaked out?

That’s very cool of you to help him out the way you did ! There are still some good people after all.

"Reg creep" would result in his first shot being abnormally higher than his other shots…not lower

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Chuck, reg creep definitely causes the first shot or first several shots to be low not high, at least if the gun is tuned half-way decently. This is because the plenum is being charged to a higher than set pressure due to the “creep”. Because the hammer strike is not changed to overcome this added pressure, the shot(s) are lower than normal. 

I’ve known a valve-poppet to have a slow leak. It would leak plenum pressure because that’s where it’s supplied from. It never showed a “creep” symptom because the reg keeps feeding pressure when called upon. It would have to be a gusher for the reg to not fill faster than the leak can dump. A plenum is filled by the reg in a few seconds.

I think your friend does have a reg that’s creeping. It sounds like he also has a leak to address being that he found one. Just my .02

In the scenario you are describing, the first shot would not always be slow. When there is a leak on the plenum side, eventually the pressure will fall enough that the valve seat will open and top off the plenum. Thus sometimes the first shot would be slow and other times it would be normal.

Is that what you observe? I got the impression from Augie that the first shot was always slower than expected.

As to the usual cause of creep, I agree it may be a bit of debris trapped in the valve seat but it has been far more common in my experience that it is due to the surface quality of the valve seat. Many times I have remedied a creeping regulator by dressing the surfaces carefully with fine wet/dry sandpaper. I reasoned that debris doesn't tend to get trapped at the seat because of the very high velocity of air rushing to fill the plenum every time a shot is fired, it will usually just blow right on through. To get stuck in the seat, it would need the unfortunate coincidence of being timed just right to get pinched and squeezed into the soft side of the valve seat right as it is closing.

This can be true. I have just replaced the o-ring opposite of that dowdy seal on my Wildcat MKII .25 after discovering leaky bubbles there (like your picture but nearest the block side). This leak was significant enough to drop from a full 230 bar to 50 bar overnight. My gun has had a Huma regulator installed for a good while now (working well, untouched) but started strangely, erratically, and randomly shooting a low velocity shot. It’s tuned to shoot JSB MKII 33.95 grain at 850 fps. Over the chronograph randomly it would shoot 850’s, 850’s, 850’s, then 775, and right back up to 850’s fps again. After repairing the leak the velocity is again consistent in the 850 fps range from the first shot to the last. Never touched my regulator or hammer spring during this o-ring change.

Airguns in general have potential to hit you with issues that seem way out in left field. Systematic troubleshooting, logical thinking, some understanding of the guns mechanics, and a little luck has helped me fix so many different issues on various guns that I’ve lost count.

Like someone stated. Reg creep will make the 1st shot low. This is due to reg creeping making the reg pressure higher. You think higher pressure means faster fps. But no. Higher reg pressure means the hammer cant struck it hard enough to open all the way. That's why you get lower fps. My impact stock amp reg will shoot 820 1st shot. Then 840. Then 3rd shot and after will be around 860-870 fps. So reg creep does not mean higher fps.

Reg creep can cause either a slow first shot or fast first shot, it just depends on how much hammer spring tension is dialed in.

I was under the impression that a recognizable symptom of reg creep is that your reg pressure gauge would show a higher BAR number than normal, 

As explained above, you would guess that would result in a higher velocity shot, but if your hammer spring is not able to overcome the valve opening resistance you would get a slower shot. It could happen either way. Very interesting.

Some confusion here? Low trajectory or low velocity? Regulator creep should mean higher pressure on the plenum side of the Rev, higher the pressure should equal higher velocity lower impact point. I think, lol.

Think of an unregulated PCP tuned with a good bell-curve. Let’s say you fill to 210 bar and shoot to 135 bar. The shot string would look like this: Begins at 860 fps (210 bar), peaks at 890 fps (175 bar) and ends at 860 fps (135 bar). You know that you should only fill to 210 bar max to begin the string at 860 fps.

If you were to fill to 225 bar, the valve is not going to open as it should when the hammer strikes it at the set hammer spring tension. You would get what’s referred to as “valve-lock”.

Instead of 860 fps you would see 825 fps or so. Each shot would gain some speed until you get back to 210 bar and you would get the 860 fps. A similar situation is going on when your regulator creeps and allows the plenum to over pressurize.