I never tried shooting it at 4500 psi, I have a head injury, but I am not insane. The rifle does handle 3625 psi safely though and I checked with the Ktal guru before trying it at 3625.
Remember while reading this, I am shooting at 11 yards.
The Kratos. is till evolving.
I swapped the 4500 psi bottle for the TalonTunes 3625 psi bottle that I had on my Texan LSS 257, as it is lighter and slightly smaller diameter and gives just a bit more clearance, but I also put a Altaros low powered regulator on it. On the highest settling on the power wheel, I get 550 FPS with Kings and the Kratos became much quieter with no ping and much less air hitting the power adjuster at 1100 psi regulator settling. I got north of 250 very accurate shots.
Then I bought a MP Mold in 48 grains, removed the regulator and put it on the original tank, it still gets around 200 shots, but with the shortage of pellets, counting the shots just to see how many I get is too expensive.
I am casting and experimenting with the MP slugs now, at 650 fps I get .5 inches at my 11 yard range and around 30 shots before accuracy falls off, at this point I do not know if it is due to impulse pressure falling, lower velocity as the pressure drops off or fouling, or all three. The slugs shoot terrible in the normal point first position, I turned them around to shoot base first and they shoot tiny groups. So a week into the experiment, I have found lower weight equals lower diameter and poor accuracy, which I have been telling you guys for years now, but at 48 to 48.2 grains, sized to .252 and shot backwards, I get a very accurate wadcutter with a nonconventual boat tail, go figure. A single shot adapter has to be used with these long slugs.
On full power, Kings shoot very well, but I had a cliff bell curve, meaning a very constant drop from 885-900 FPS, but due to the large bottle that drop us very gradual. I removed the stock and adjusted the hammer spring out to 1/4 turn and do get a few shots that actually climb from 870- 875 FPS or so then decend in FPS, but not many and that 1/4 turn is as far as it goes. I tried tuning it up for the slugs, it does turn a few turns, but no noticeable increase in velocity. So for now it is either a 47 FPE rifle running flat out with either Kings or the 48 grain slugs, or a very sedate, accurate low powered shooter with the regulator.
As it comes from Benjamin, the rifle does not need a regulator for full power use or turned down for plinking. It shoots like a regulated gun with a balanced valve due to the large air storage and effortless sidelever function. I added the regult9r as I shoot indoors and wanted a very quiet rifle, and the regulator removes the annoying bottle ping. Also remember when you turn that power wheel down, it is a non repeatable air steangle adjuster. That restriction is getting hit with the full air pressure regardless of the lower velocity and being as the power wheel has no setting detents, getting it to return to a low powered sweet spot requires use of a chronograph.
With a regulator for low powered shooting it is as mentioned above, a very quiet rifle and very accurate, but not something that has to be done.
A note about switching bottles, I have done this a dozen times or more, other than the initial sanding the stock channel and using a lot of air, you have to depressurize, I have never experienced a leak doing this.
Hope this helps, be careful and safe,
Roachcreek
post script, I got the 3625 psi cf TalonTunes bottle from TalonTunes, but have no idea what it costs in this post Covid world.