I'd go with a Marauder and tank setup. If you're in Florida there'll be plenty of scuba shops around to fill a tank for you. You can pick up a used tank for < $100 that'll fill your rifle around 80 times, and depending on the caliber, get you 24 to 50 shots per fill. The smaller calibers use less air per shot and generally are a bit quieter. I love my .25 Marauder, hits hard and very accurate. I don't know how hard lizards are to kill so not sure you need a .25?.
Good idea on the tank, although I think you would want to go with a SCBA tank that is 4500 psi vs 3000 for scuba.I get about 20 shots with my .25 before I pump-figure 4-5 pumps for each shot,so if I shoot 20 I plan on 100 strokes on the pump.Great exercise.
Is the tank necessary? I thought you could recharge these things with a hand pump.
No, not necessary, but much easier for high volume shooting. I also have a hand pump in case I have to recharge away from my tank, but those things are, as JimH says, "Great exercise"! Pumping to 3K psi is not easy.
Another option for you to consider is the Marauder Pistol. Comes with a shoulder stock and is much handier than the rifle. They have it regulated for 2500psi out of the box so easier pumping. Been thinking of getting one myself.
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