savage 340 bolt cocking problems

help, hello everyone i have a problem that i hope the folks here can help me with. i have a 340 30-30 when i cycle the bolt the fire pin does not always stay in the cocked position, it slam fires sometimes.
i can open the bolt an put safety on an it will slam fire when i close bolt ???, it will not do that when i have the saftey on fire
i have not done any modifications to it , it just started to happen at the gun range. i did buy the gun at a pawn shop about 2 years ago it been a very good rifle . Or should i just take it to the gun smith .please give your opinions thanks james

I do not currently have one around to look at. It only dose it with the safety on?

is everything clean?

b/avenger well i cycled the bolt about 20 times with safety on and off [10timeseach] and it fired 3 times with safety on ???
ef bell the action is not very clean but i will take apart and clean. hope it is as simple as that.
this is my wife,s rifle and it messed up while i took it to the range [her favorite rifle] so any and all help is apreciated
i ll try to post pics of action soon thanks james