TargetTalk

I have an AR20 that won't shoot.
Tank is topped off... and tested multiple tanks that are working in other guns.

It started by shooting just a little bit of air and has regressed to no air at all.

I can confirm that the tank is fully seated and I hear no air escaping when its tightly screwed into the receiver.

When I remove the tank I hear the typical brief air (pfft!) escape. It seems like the air reservoir or regulator is not engaged?

Any thoughts?

It sounds like your regulator is bad. You can send it to Umarex to repair or order the part and install it yourself. You will need to tell them which regulator you have since they have a 10m model and field model.

The regulators are almost always based on a belleville washer stack. They usually stop working when they get a bit of corrosion on them that prevents them from sliding along each other in the stack. Many times a bit of 100% synthetic oil oil introduced where the tank mounts to the rifle will shake it loose as the oil is blown thru the gun. The regulator needs to be serviced, but a lot of times all that means is to oil it well...... DO NOT USE ANYTHING CONTAI ING Petroleum Distallates in the gun, they are notoriously hard on rubber o rings.