I got a Gauntlet G2 in .22 a few months back. It didn't have any rattling sound in the tank, but it didn't hold air. I sent it back and got a replacement. The new one holds air. I still had a few problems though.
Virtually every single screw was loose on it. I mean everything! No idea how it could have left the factory like that. Quality control is not good.
I went over it and tightened up and blue Loctited everything. I also put on a Hajimoto Baffle Stack and High Performance air stripper and vented the shroud.
The edges of the slot in the receiver where the magazine goes were razor sharp. I cut my finger pretty bad on them. I took a file and fixed that.
It is a real pellet picky gun. Pretty much all it likes are the 25.39 JSB Redesigns and the FX 25.39. Doesn't like slugs. It's accurate and powerful with those 25.39 pellets. (45 ft lbs) I do get a lot of shots out of it with that 24 cu in tank. I like it now, but honestly I can't recommend buying one based on the problems and quality issues I had. I'm going to hang onto it though.
I was looking at the 30 Gauntlet, but now I'm not so sure. I think I'll look elsewhere.