Best springer under $300

Yet another in favor of the HW50s. Even throw out your qualifier of $300 and I'd still say HW50s in .177. Mine beat out an HW77k, two FWB Sports, and an RX2, all springers in the $500-700 range. I still have the HW50s and the rest went on down the road. Have shot friends tx200s and they didnt do much for me, at least not to the point of buying my own. The Walther LGU is up there as one that still interests me, after shooting a buddies, but price is around double your $300, and I think I heard they're not even made anymore so it'd be used market. 

So, yep, HW50s x6 or 7 (rough tally of above votes plus mine). 
 
Another vote for a Diana/RWS M34 -

I favor the TO5/Panther version, either caliber

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