Tuning Hm1000x reg inconsistent readings

[corny]

Long story short, I got my rifle back from airgun usa/Martin two week ago. At that time the reg had completely failed.

I had them do a complete service, including new reg piston. Gun shot great when I got it back 

fast forward today…I’ve been noticing groups starting to open up. 2” at 75y. 
cleaned barrel and shot over crony, was doing 875-880 increased HS, no real increase in speed.

Pulled reg, installed in best filling test fixture. Got 118bar

Turned it up to 145 bar, and tried tuning the HS, can’t get it to settle down. Shooting 875fps ish till bottle pressure reaches 190 bar, that it slowly climbed up to 895fps till it drop of the reg. 

I got the reg back in the test fixture and slowly bled it down, by pressing the bleed button mimicking shots.

reg is showing very slow recovery,right after shot recovers to 143-145, but will creep up to 149-153bar if left sitting for couple minutes. But as stated above, doesn’t seem to creep at much under a 190bar fill. 


Issue is driving me nuts…I just wanna shoot. 

 

[mubhaur]

That is strange. I have rebuilt my RAW reg and it is the most consistent reg I have ever experienced. 

 

[corny]

I can only assume, Whatever damaged the reg initially, must have damaged it again. 
Airgun usa thought it was over pressured, but I know now it’s never been over 230bar since I got it rebuilt 

 

[mubhaur]

I can only assume, Whatever damaged the reg initially, must have damaged it again. 
Airgun usa thought it was over pressured, but I know now it’s never been over 230bar since I got it rebuilt

I always fill my RAW at 250 bars after reg rebuilt and reg upgradation. No issues at all. 

 

[SpiralGroove]

Hey corny,

This is something I've never experienced with my HM1000X's. 

- The only thing I can think of is the Belleville Washer group or the seat. Most likely the washers ... 

Changing the seat to Peek ended all my creep issues.

 

[corny]

are u thinking the washers are incorrectly stacked? 

 

[mubhaur]

are u thinking the washers are incorrectly stacked?

Looks like it has a bad sealing seat. 

 

[SpiralGroove]

are u thinking the washers are incorrectly stacked?

What caliber gun are we talking - .25?



Take a pic of your stack ... could be bad washers too?



Otherwise, send me you reg. stem and I'll install a new seat (PEI) for $25 including shipping.

 

[corny]

Yes it’s a 25cal.

I really appreciate that spiralgrove…might go that route.

but I’ll tear into the reg first, see how complicated it is, 
I do have some 5/8 peek on hand, might be able to turn it myself. 
from what I gather, this is a small cylindrical part inside the brass piston? 
how do u get that out? Drilling it out in the lathe? 

 

[corny]

I’ll post pics before u tear it down, and as I go…

 

[corny]

What’s really baffling about this rifle, is that it was shooting 891fps when I got it back from service.

I had to tighten the HS at least one full turn to get it into that range yesterday. no way did the HS back out on its own….not that much. I just wish I had pulled the reg back then and tested it. 

 

[zx10wall]

Sounds to me like you have the reg set too high. If Martin had it set to 118 bar and you only wanted a bit more speed, you just needed to bump it up a small amount. 10 bar will increase speed approximately 25 fps once you dial in the needed hammer spring tension. Sounds like you have it way out of harmony now!

 

[corny]

Yeah your right…

But keep in mind this is tuned for 34g pellets.

it most certainly didn’t leave airguns USA at a 118 reg setting. 

 

[corny]

Showing the reg washer stack. Also showing the inside valve on bottle..is this normal wear? 

 

[corny]

Piston, appears the plastic end piece was crimped, can see markings in the side and front face. 
also appears that the plastic also plugs the hole made though the center of the piston. 

 

[mubhaur]

Piston, appears the plastic end piece was crimped, can see markings in the side and front face. 
also appears that the plastic also plugs the hole made though the center of the piston. 

Again looks like a bad sealing piston seat.

 

[zx10wall]

Yeah your right…

But keep in mind this is tuned for 34g pellets.

it most certainly didn’t leave airguns USA at a 118 reg setting.

Gotcha! Didn't know that info from the initial post. Yes, the reg seat doesn't look too healthy. 

 

[corny]

Drilled out the old seat. Bored the hole true with a tiny carbide boring bar. And press fit a piece of peek .118” in diameter. 
Regulator appears to be a lot crisper. Recovers a lot faster
I’ll leave it on the tester for an hour see what it does 

 

[corny]

Between adjustments I noticed the top washer isn’t sitting on the machined cylinder of the shaft. So it shifts of center completely changing the reg readings 

can I machine the knurled nut…to give the stack more room? 

 

[mubhaur]

Between adjustments I noticed the top washer isn’t sitting on the machined cylinder of the shaft. So it shifts of center completely changing the reg readings 

can I machine the knurled nut…to give the stack more room? 

Try to mirror polish the external edges and internal edges of all washers equally