I have a 22 gauntlet and can probably answer a few questions, although I am nowhere near the level of some of the expert modders out there!
You can increase the reg of the 22 up to 1500psi (recommended is 1400 max). You have two real options of doing this, you can buy the flex reg from hajimoto/ninja, or you can take the reg apart and add shims to increase the power. The shims are going to run you about $8 in parts, the flex reg is going to run you $159.00. The flex reg you can fine tune the pressure, the "redneck reg" you will have to take apart to adjust it.. however 99% of people just max it out and leave it.. me included.
The other major upgrade you want to do is the STK kit from hajimoto. This is going to improve the function of the gun, while giving you adjustable hammer spring to fine tune the gun as well.
https://hajimotoproductions.com/index.php/product/super-tune-kit-for-umarex-gauntlet/ Other than that, there are a few other optional upgrades you can do... you can add aftermarket baffles, air stripper, 2-stage trigger, tank size upgrade.. etc.
However... as a stock, out of the box gun, the gauntlet is a fine PCP for target shooting. Mine really liked JSB 18.13gr pellets, just under 3/4" groups at 50yds, about an inch or so at 75yds. It shot these 780fps stock.
I tried to turn mine into a hunting gun, and had limited success. I tuned it to like the NSA 17gr slugs at 815fps, it shot them 3/4" at 50 and 0.6" at 75yds. Problem is the thing weighs like 13lbs with scope, so was awkward to carry around the woods. And it is LONG, I mean REALLY LONG, so I kept hitting the shroud on small trees or what not just because I'm not used to carrying along what feels like an 8 foot 2x4 through the woods. Every time you touch that barrel, the POI shifts.. even with barrel band. So I'd have to hunt one area, then go back to the truck and re-zero my scope, and start over. I tried every mod available, plus aftermarket barrel bands, and new scopes and rings. Eventually I'm to the point where I'm done with it and moving on.
Now lets talk cases, because it wont fit in one. Like I said, its long and its tall. You will need a double-rifle case or XL soft case for it.. the hard case I got that it fits is a hassle to lug around and barely even fits in a vehicle. But without it, you'll knock that POI off before you even get around the block on the way to the range.
Would I suggest it? If you want to toss a few hundred into it to have a pretty cool target gun then absolutely. The thing shoots laser beams and honestly is a riot to shoot from a bench. You can even leave it stock and just go shooting and I bet you get good groupings out of the box, everyone I have talked to that owned one did. If you are wanting to pest, hunt, or just want a gun that you never have to "re-zero".. Dont do it.
Thanks man. Great things to think about
, not as cheap as the Gauntlet, but 5 yr warranty...Marauders seem to hold their value pretty well, too...