i'm not good on internals, but look to make sure the round is going into the chamber far enough to allow the gun to lock up properly.
remove the barrel n take a feeler gauge for comparison and see how much of the case head protrudes "above, even or below flush" with the chamber end of the barrel.
take the feeler gauge n see how much barrel to frame gap there is with the barrrel on the action. close the action on consecutively thicker blades till it just does slide out without binding. this should tell you your "barrel to frame gap".
if the factory round sits below flush with chamber
...... or if the factory round sits above flush more than the measured barrel to frame gap, it will not allow the action to lock up.
also.........does the GNR barrel by reeder have a short throat that will not allow that bullet/loaded round to go deep enough into chamber to lock up? meaning the bullet is engaging the lands too hard to close on.
hope this helps....or at least begins the process of figuring it out.
30-30ackley improved rounds will fire standard factory 30-30 ammo. not sure about the GNR improved cases
surely gary reeder could help ya out on that.
if none of this helps.............i've heard of hammer springs in the action getting weak and needing replaced.