My Avenger does not have a breech o-ring. There are two o-rings on the pellet probe that seal that area so no worries about damaging a breech o-ring. I use goo-gone to clean new barrels and non-chlorinated brake cleaner for subsequent cleanings. I have recently been using Johnson's paste wax...
I love shooting steel and have many AR500 targets and a KYL. Steel gives you instant visual and audible feedback and a quick spray of white paint instantly renews the target. Especially like that quadrant target. It was the most fun target to shoot at the 2019 GTA Fun Shoot.
The same thing happened to me when my valve stem broke at the 2018 GTA Fun Shoot. I had several pellets stuck in the barrel before I realized that the valve stem failed. I degassed and disassembled the gun and pushed the pellets out. I then sent the valve to Troy Hammer for repair. He made it...
That Huma-Air setup would be ideal. I have seen where someone used a P-Rod gauge block near the front of the air tube to add a gauge to show the air reservoir pressure. It requires drilling a hole in the air tube to thread the gauge into the gauge block. It will reduce the volume of the air...
I've had my YH for over 4 years without a rebuild and regularly fill my three 30 min. SCBA's from 3000 psi to 4200 psi. My temps never get over 45C and I use Mobil 827 Rarus oil. I use lots of ice directly in the water bucket and found that this keeps the temperature much cooler than using ice...