Besides the Airforce Texan .257, what other high end airguns use .257 caliber?

I was on the preorder list for 3 months for the FX Impact M3. Not knowing when the M3 would arrive, I decided to buy the AirForce Texan LSS .257 in the meantime. I only plan to shoot 200 yard + with both the Texan and M3. I stocked up on .257 slugs for a few different vendors while waiting for the Texan to arrive. Then FedEx lost the order! The vendor I ordered the Texan from is processing a complete refund.

The same week that FedEx lost the shipment, I got the call that the M3 is back in stock. Now I have $200 worth of .257 slugs.

Now that the M3 is a dedicated slug gun for 200 yards +, I'm looking for the perfect .257 caliber "all around" airgun besides the Texan. Don't get me wrong, the Texan is still a possibility to return to the lineup, but I'm looking for recommendations for other .257 guns.

What other guns use .257 caliber. Price is not in question.

Amendment: Can I shoot .257 cal with my M3? Whats the worst that can happen if I did? Pros and Cons? 

Rod in San Francisco
 
I believe the Texan is the only manufactured.257 on the market. The others are all some sort of conversion. My personal favorite conversion is the Winchester 35-70. Other than the Evanix sniper , it’s the only rifle that has a magazine capable of taking bullets over .55” long. Perfect for the 257420 cast bullets . I’ll be contacting CARM soon to see if they can make a replacement mag specifically in this caliber rather than having to modify the existing mag.