Umarex Notos Issue - POI Drop Off

[Kiang]

Hello Everyone,

I charge my Notos up to 3600 psi. When I reach about shot 9 or 10, I start to notice the POI is dropping about 1-1.5 inches. After about shot 13 or 14, my POI is 2 inches below its original zero. I am shooting at about 30 yards using a Vortex 1-6x24 PST and unfortunately do not have a chrony to test the shot string. I was wondering if any of ya'll had this issue as well? I had a few theories that I may have debunked, but your thoughts are appreciated:

Parallax Issue - The PST does not have a parallax adjustment, but the POI seems to always be on point after I charge the gun unti shot 9 or 10. The shots are also perfectly below the point of zero, so the windage remains perfect.

Magazine Issue - I am using a 12 shot magazine. Going to use a single shot tray today to see what happens around shot 9 or 10.

Loose Screws - All screws have been tightened prior to shooting

Dirty Barrel - I cleaned the barrel and have shot about 100 pellets to "season" the barrel.

I understand the Notos should have about 21 regulated consistent shots. I am confused as to why the drop off after 10 shots.

 

[2fast2furious]

Get a chrony. My notos shoots very accurate up to 30 yards. That's as far as my range is. It gets about 25 shots b4 falling off reg. Shooting jsb 15gr around 740fps. Try cleaning barrel. A dirty barrel will affect accurate. Also you shooting blind if you don't own a chrony. It's a must.

 

[Pea-shooter O.G.]

Which gage are you looking at when filling. The guns gage or a tank/compressor gage? The reason I say this is because I recently got a Notos and found the gage is off by 400psi? When I fill my gun using a tank, the gage on the gun shows 3200-ish psi when my tank fill gage shows 3600. I trust the gage on my tank as it shows the same pressure against my Daystate Mk4. Maybe your gage is inaccurate? Makes me curious if any other Notos owners have had similar gage inaccuracies. I haven't run it over a chrony for a shot count, but its gotta be over 25 shots or more before I can hear difference in the sound.
Also, like stated above, a chronograph is a great/necessary tool to help qualify performance.

 

[Firewalker]

I've seen 2 gauges go bad, both replaced with UX gauges.

Never seen a Notos drop POI, I shoot 2 mags through all my conversions.

Sounds like low fill or bad regulator.

 

[Gramps]

My Notos is OTB when it come to reg pressure & hammer spring, I’m only betting about 17 shots before the POI starts to change. Been filling using the garage on the gun. Will check it against my pump gauge didn’t think of that being the issue.

 

[midwest]

I use a scuba tank to fill my Notos so I don't get a full charge but I can get 18-20 shots before I see a drop off.