This is a bit off topic but I have never used a compressor for an Airsporter / Mercury. For both stripping and rebuilding I clamp either the action or the trigger block in a padded vice and unscrew the 'other bit' from there. I wear leather gloves and put a towel over the threaded part until the threads give. For reassembly with an Airsporter I find it useful to clamp the trigger block in the vice and offer up the action. I have a wooden block with a recess for the muzzle to sit in. I find this gives good control. Maybe not so useful for a Mercury because of the possibility of the action breaking while trying to engage the threads so in that case I would clamp the action or work without the barrel attached.
No matter though .. good idea above.
On my compressor I have rarely run out of distance but a FWB 124/127 did defeat me (and an Original 66 came close) so I had to modify my compressor to shift the 'action stop' further away.
Cheers, Phil