Hi both are good rifles One thing to consider is there are more companies producing 357 pellets then 30 cal pellets. That being said if you find a pellet you rifle likes stick with those. Hope this helps with your decision. Dave
Although a .357 is cool, the .30 is probably slightly more versatile as an everyday medium to large pest eliminator. That being said I have this strong desire for a Slayer .357 with wood stock
I dont think Hatsan makes their Carnivore in non-QE, however you can remove the shroud and add an after market ldc. Im guessing you would need the Hercules heavily modded to shoot .357 close 1000fps, but could more easily get in the 900s with the Carnivore .30 if sticking with the Hatsan. You did not mention if considering others, so I wont either, but of course there are other options. My Carnivore .30 was quite accurate and easy to maintain. Though not a Hatsan, Ive had .357 to compare and first off is what Dave pointed put, not many options for ammo in .30, though most seem to do well with JSB 44.75gr if not 50gr. You tend to get more shots in a .30 as well as greater quantity per tin for ammo. As most will advise or otherwise interject, neither are plinkers, .357 less so. But thats potentially personal depending on your plinking. Both are enjoyable to me and offer a different experience, however the .30 has always been used much more (I will and do "plink" with any caliber). For me, the .30 just provided an obvious advantage in shot count, but still a large enough projectile for my me, over .25 and smaller. It is also still quite useful/acceptable as a critter taker, in fact my most recent .30 is so accurate I use it for the little buggers that ruin my rock walls. The .357 has an obvious advantage in power, especially if you decide to expand your consideration to other platforms, eg Ive seen modded Evanix shoot .357 in the 900fps + range, more than modded Hatsan (again, remaining in the realm of lower cost repeaters). The Carnivore .30 is a great shooter for the money, and could leave enough to then get a refurbed Recluse to tickle the .357 bug, as you might get one that shoots JSB 81gr in the 900s out of the box. Then of course there are others...........
With mod's the 30 cal bt65 platform will push 100fpe with 50gr jsb and get 5 shots maxed out, mid tune in the 90ish fpe will get you 7 shots. I like 7 shots on mine. I never tried the bt65 35 cal.The Hercules has stupid potential but is limited by size of pellet that can fit.
I happen to own a Hatsan BT65 .30 Carnivore; Elvira. She's close to a hundred or more squirrels in my 8 month ownership. I've had it modified by Baxter Walton and it's shooting around 80 FPE.