I have a spr 453 that a bought used for the purpose of retiring my bps 10. Gun works great with everything but 3.5" shells when i fire them the gun fires, the next round ejects out of the magazine onto the carrier but the bolt locks back. The only way to release it is to reach in and move the shell on the carrier slightly to the rear. Any ideas on how to fix this or where else to ask would be greatly appreciated. Thank You