As Jimmy mentioned, you might have a shift that can misalign your bolt probe in relation to the transfer port once you loosen all of the main bolts to slide the air tube out. Before you loosen anything, take note of the position of your trigger. The main shaft should be pointing straight down...or close to it, that's number one. Number two is to take your magazine out, close the bolt and mark it where it meets the barrel. More accurately, where it disappears inside the barrel. Use a box cutter or an Xacto knife to scribe a mark on the bolt. When you put the whole thing back together just be sure the trigger is straight and the mark on the bolt is where it's supposed to be before you tighten it. You'll be fine.
Mine is a Mk1 .25 and I set my Huma at 150 bar to get 33.95 grain JSB's up to 850. that's where the gun is "in harmony" and the most accurate with those pellets. The only problem I had was the main O-rings that seal the regulator in the air reservoir. I kept blowing the front ring. Despite extra care and lubrication I went through 3 before checking with the guys at HUMA. I got SUPER response by text from those guys and they said it was a problem they had run into before....when the air tube is on the large side of spec or the reg may be slightly on the small side. The cure was to go with a BS119 duro 90 rings, 2.62mm thickness. Mine was from The O-Ring Store and was a model U90119 aka AS568-119 U90 EU Polyester. It fixed the problem and this thing doesn't leak a drop of air. I'm really happy with the extra power and consistency, I'm sure you will be too. Enjoy!
Glenn in Texas
