The context in which Jesus said to turn the other cheek was instructing his disciples on how to conduct themselves.
If slapped on the cheek turning the other, if sued for a cloak give two cloaks , if required to carry a pack for a mile , carry the pack two.
Then he and most of the people he told this directly became martyrs.
Lots of Christians since became martyrs, this is a high standard of service.
Wasn't long after this instruction that he told his disciples to make sure and buy some swords.
Then when he was being arrested one of his guys started to put up a fight, ... but Jesus stopped him , told him to put his sword away and performed a healing on the wound.
I think Jesus was making it clear that he was going willingly into martyrdom , not being surprised and overwhelmed when helpless.
This is a serious subject, is a gun a waste of money , if you havn't the will to defend yourself with it?
Not necessarily, there are indeed circumstances in which having a gun can serve the cause of peace , and times when it does not.
If you have the gun , you have the choice to use it , or not, and you can choose to be injured rather than shoot , if this is what seems right.
But if you havn't prepared , not only with getting the gun, not only with practice and proficiency, but also with serious thought and prayer. Then you are not being a free agent and making choices at all.
Whether you get a gun or don't but especially if you do it is worthy to settle within yourself what the decision is and why sooner than the need. So that when the need is present the decision doesn't take all day, and isn't wrong for you.