Stuck brass can be caused by several things, up front are too hot of loads and dirty/oily chamber or brass. If it's sticking with factory ammo, try a different ammo, even some factory is too hot. Polish the chamber as shown in the FAQs, if it still sticks, you can increase ejector spring pressure by installing a BB in front of the spring, ejector R&R is covered in the FAQs also. If all else fails, contact H&R, it may have a defect in the chamber that no matter what you do, it won't help.
Tim