24 - V question

A Savage 24 I have is a 24 V, 30-30 over 12 GA 3 inch, plastic furniture and dull finish.  I have not shot it all that much.  Shot 3 or 4 rounds of trap, a few ducks and one deer.  I cannot recall when I bought it, but it must have been in the 1990's.  It was new but not quite unfired when I bought it.  It is utilitarian, fits me only with the addition of a lace-on cheek-piece, surprising strong felt recoil for a relatively heavy gun (with slugs and duck loads), and in my view could have been better designed as a shooter (which is its purpose of course).  It is accurate for this sort of gun.  It is OK for berry picking, cutting firewood, walking into a beaver dam to fish, and beach combing, but 4 times in 5 I instead carry a .44 revolver for those sorts of outings.  I live in a rain forest, and the house is on salt water.  We not only have lots of black bears of every color, or almost every color, but we have brown bears.  Brown bears can be fearless, and if accustomed to deer hunters they sometimes come looking for something to eat when they hear a shot. A 3 inch, 12 gauge slug has a lot more snoose than anything that can be shot in a .44 revolver.  

Yesterday I loaded up some very light loads using cast bullets.  115 grain spire point with gas checks, and 115 grain flat points with plain base.  I sized them .309 and .311 (seem to lack a .310 die).  9 grains of Unique (as the 1 cc Lee dipper gave me that weight, and I merely wanted a light load).  They shot well at 50 yards.  I think it liked the .309 best but didn't shoot enough to be sure.  I would have shot more but many didn't go off.  I would have attributed it to old CCI garage sale primers but the primer indentation was very light so I think that is the problem.  I had no 12 gauge shells with me so could not see if that too was striking light.  Before I go tearing into the gun does anyone have any ideas about the light primer strikes?  Thank you.