Sig Sauer P-250 Pellet Gun- Mag Won't Release

I have a Sig Sauer P250 pellet gun. It is only about three months old, so still under warranty. 
I fired it this afternoon and, once the CO2 cartridge began to get depleted, the mag won't release. There is also a pellet stuck in the barrel. Is there a way to disassemble the gun, clear the barrel and get the mag to release or do I have to send it back to Sig? 
Thanks.