PP700 adventure started(Artemis PP700s-a)

[nervoustrigger]

Wayne, I do not know of any way in which a regulator acclimates to a particular pellet but there are a variety of general regulator behaviors that can be gleaned from these shot strings.
 
On the first string, shot #1 being so fast suggests the regulator is creeping and the pressure in the plenum was higher than normal, and also that the hammer strike is adjusted higher than it needs to be (else that first shot would have actually been slower due to partial valve lock).  The fairly large up and down swings (546 -> 573, and later 567 -> 597) could be a variety of things…the regulator, hammer strike variation, pellet variation, or some combination thereof.   The strange thing is the uptick that occurs at shot #11 where there are a few at 580 before going back down for a couple at 550-560 and then back up again to 590.
 
Were you holding a steady pace between shots?  If not, that probably explains the ups and downs, particularly in light of the creeping issue a lot of us have experienced.
 
On the second string, there’s more of the same…another high shot #1, then some lows of 550 and highs of 590.  Had a pretty good run from #8 through #22.  That’s what we’d like to see all the time, whether it’s been resting 5 seconds or 5 hours.
 
There is one other possibility for shot #1 being hot.  After it’s fallen off the reg, when you refill, the regulator doesn’t close in the same manner as it does in normal operation so the plenum pressure may initially be off from where it would normally be.  Still I’m more inclined to think creep based on this reg’s reputation.

[Wolverineshooter]

In my most recent test, the first shot after refill were about 120fps higher than the second shot. This is not always the case, sometimes they behave well, producing speeds consistent with next few shots.

[Thane]

I have to wonder how much the single loading with fingers makes for variance. The cheap crosman hollow points I commonly  use for chrono strings load in the breach with great difference in finger pressure, some no resistance others take some force. The softer skirted models load with far more consistent finger pressure, but could still seat differently. I'm thinking about using a ball bearing to press the pellet in the breach, making it more consistent. I don't know if it will show up in a string...

[nervoustrigger]

It’s worth a try.  I’ve noticed the skirt makes more of a difference in low pressure rifles like CO2, less so with PCPs operating >1500psi.  Depends on how hard and thick the skirt is as you might imagine (how easily it expands out to fit the bore when the pressure pulse hits it).

It so happens I was using some cheap Winchester pellets for the 20 shot string I posted last night.  Some had to be pressed into place and some dropped in almost 1/8” before the skirt grabbed to keep it from slipping down the barrel.  Nonetheless the velocities were consistent, more so than I would have expected to be honest.

For conventionally shaped pellets, the head does not have enough contact area to represent enough friction to make a meaningful difference.

[Wayne52]

Jason when I do take this gun hunting I always shoot the first shot in the ground and the POI always seems to be good after that but if I don't the first shot doesn't hit the scoped POI.  I've had good luck doing it this way.  Also I know that the lighter pellets won't produce as many shots on the regulator like the heavy pellets do.

[nervoustrigger]

Wayne, yeah that's probably workable for woods walking provided the creep is sufficiently slow.  Just have to know the gun. 

Not very feasible for a long covert session in a hide so I suppose it depends on the circumstances.

Creep drives me crazy.  It's probably as much a psychological problem for me as it is a real problem with the gun.  It erodes my confidence and makes me nervous to take the shot.

[nervoustrigger]

Holy long shot string, Batman!

I thought it was going to cross the 100 shot mark but ended up with about 90 useful shots.  Clearly something was happening that caused the velocity to move upward.  I suspect it either has something to do with the hammer spring being completely backed off or perhaps it is the tapered shoulder of the regulator screw displacing material on the plastic washer and causing the setpoint to shift up slightly.

Whatever the case, it looks like the regulator is working and there is no creep.  I think I'll put some more shots through it for a few days and see if it settles in before I monkey with anything else.

[mackeral5]

That's amazing, 90 shots out of a pistol.  Awesome job!

[Rallyshark]

That's a lot of shots right there!  I use mine for critters, and sometimes they aren't very close, so I keep it shooting on the hot side.  I don't know how many it would shoot at those velocities with the Huma though.  I suspect it would be a lot, but I don't know about 90   

[nervoustrigger]

Thanks guys, yeah hopefully I can get that weird rise sorted out because it would be nice to have a long stable shot count for practice.  Last night I gave the hammer spring about 1/4 turn more and threadlocked it.  That put just a slight amount of preload against the valve stem.  I’ll see what that does tonight.  If it helps with consistency, I won’t mind trading off a few shots.  Frankly I’m more excited about the prospect of getting rid of the first shot variation. 

[bandg]

Jason, I think you were on the right track in 1426 but for a different reason.  I haven't worked on mine for quite a while due to family issues but when I went through the pistol I followed all the good advice I had read on this forum and started working on it.  I smoothed all edges on the Bellevilles and while working in that area I noticed that the small SS screw that passes through the while washer was a VERY loose fit in it's threads.  I could not see how that loose fit could avoid "walking" as the screw was loaded/unloaded during reg piston movement.  I lined the piston hole where the small SS screw goes that passes through that white sealing washer with either JBWeld or polymorph plastic (can't recall which I used right now but I believe it was JBWeld).   I put a very light coat of oil on the screw threads then put JBWeld on the screw threads and in the piston threads and seated the screw to depth in the piston.  When the JBWeld started to set, I kept giving the screw a slight turn out and back in every few seconds as the JBWeld was setting to prevent it from sticking to the screw.  It ended up with the JBWeld well attached to the piston but not the screw.  The screw was removed and cleaned off and any excess material was removed from the top of the piston where the white washer sits.  The screw would then screw in to full depth as initially measured but it was much tighter in it's threads and did not move as freely.  After that, my pistol was much more consistent.  I've posted about this before in one of the older pp700 threads.  The depth of the screw into the piston is critical for proper regulator function and some careful measurement must be made to make it function correctly but this is posted in the older thread as well. 

[nervoustrigger]

Very interesting, thanks for your well articulated thoughts.  Yes I had a similar concern when I rebuilt it the first time, that the screw would tend to walk as it and the piston cycle back and forth.  I applied some threadlocker to ensure it stayed put, and for what it’s worth, they were still firmly affixed when I disassembled it a couple of days ago…meaning at least that wasn’t the reason mine had started to not regulate properly.
 
And yeah I really don’t know the magic amount of piston travel to allow.  I eyeballed about 1mm this time around.  The previous time, I think it was probably only about half that much (0.020” or so), figuring as long as it can open at all, high pressure air will find its way through.  Twenty thousandths might as well be a mile.  Maybe it would affect its recovery time but what do I care if it takes 5 seconds instead of 1?  And since the Belleville stack has so little travel, intuitively I thought a short throw was necessary, else they wouldn’t be able to compress enough for it to close.  If there was a good explanation in another thread for how to set it, I would love to
read up on it.
 
Of course this time I changed 3 things at once so I don’t know which of these is the important difference, or if perhaps there is some combination that’s important:
1.       Stacked 9 Bellevilles in single series
2.       Flipped over the plastic washer so the screw’s taper can seal off against a knife edge
3.       Left about 0.040” piston travel rather than about 0.020”
 
Oh, and this reminded me of something I wanted to mention.  When I was degassing for this recent rebuild, once the pressure got down fairly low, I just pressed the hammer against the valve stem to evacuate the rest.  But rather than hissing, it was just barely weeping the air out.  The regulator should have been wide open and dumping air out through the valve in a hurry.  I really have no idea why that was happening.  Way slower than my 0.020” gap would dictate.  At first I thought maybe the brass piston either had too much or too little travel and its O-ring was blocking the high pressure aperture from the reservoir (the angled hole drilled into the regulator body).  But after getting it apart and looking at it, I don’t think that’s possible.  To me that’s a clear sign the reg wasn’t acting right but I could not make sense of why.

[bandg]

I thought I had reasoned through how this system works when I was tinkering with it last year but I remember that it is not very intuitive and I can't get my head around it again right now.  I certainly don't know if it is "normal" regulator function as I am not well versed in regulator design but it certainly doesn't seem to be "logical" to me so I'm wondering if there is function in it that we don't understand well.

[mccastro6]

MikeC here from North England.Since getting the .117 ( black square shroud) version of this pistol a couple of month ago,i joined this group and have lurked in the background soaking up the great knwledge here. i learned here a while ago,,that there was a facebook group with a good info section,i am a member of Fb.i found the group about a month ago but did not join at the time i found it.i Used the info that you/link that you guys kindly posted and at that time it worked,but today (24-09-2018) nothing.Can any of you guys tell me if it has been closed or just glitch with Facebook.

[Wolverineshooter]

Just checked the FB, Not working for me either.

[bandg]

Hopefully temporary as that group also had lots of good info and pictures.

[Rallyshark]

Some idiot reported the Facebook group, and FB shut it down   Klaus(the admin) is trying to get it back up. It was likely someone in the UK that reported it, since it is a UK based group. There are folks over there that will do anything to shut down a group even remotely gun related.  Wankers

[Wolverineshooter]

It's sad but there are plenty of people thought all gun owners are future criminals or cruel.

[mccastro6]

Hope he(Klaus) can get it fixed,if not he should try to bring his experence with this pistol here.Would be a shame to loose the great Info he has accumulated.

[Wolverineshooter]

Hope he(Klaus) can get it fixed,if not he should try to bring his experence with this pistol here.Would be a shame to loose the great Info he has accumulated.

good idea. just transfer here. avoid FB or google police