Since guns did not exist when Jesus walked the earth, we would have to extrapolate. Did Jesus condone his follows owning a lethal weapon? The answer is YES. Swords were clearly weapons. They don't serve another purpose. In Luke 22 Jesus encouraged his follows to purchase swords.
35 Then Jesus asked them, "When I sent you without purse, bag or sandals, did you lack anything?" "Nothing," they answered.
36 He said to them, "But now if you have a purse, take it, and also a bag; and if you don't have a sword, sell your cloak and buy one.
There are also countless examples in the Old Testament of God condoning warfare, self-defense, and defense of one's family. I think this is one of those issues that falls under Ecclesiastes 3. There is a time to kill and a time to heal. I'm not advocating senseless violence, but the context of Jesus telling the disciples to purchase swords and then reprimanding Peter for cutting off the high priest's servant's ear seems to indicate that he intended the swords to be for self defense or for a deterrent, not for a pre-preemptive attack.
This is what I was going to say. Ecclesiastes 3:1-8 says a lot. "A time for peace, a time for war", "A time to kill, a time to heal", etc.
Does anyone really believe that Jesus would have told the Jews to disarm themselves and be vulnerable to their enemies? That would be suicidal against their many enemies, so, no, Jesus wouldn't have told them that.
Defending ones self, family, friends, innocent strangers, those who are unable to defend themselves, your property, your country, etc, etc are all valid reasons to use a weapon.
I can't attest to it, because I'd need to study the verse more, but my take on "live by the sword, die by the sword" is that if you use violence as a solution to every problem you encounter, eventually it will come back to bite you. Use your best resource, God, before taking violent action. Ask the Lord for wisdom. Try to make peace with others by "pouring coals over their head" in order to melt their icy hearts. Try peaceful methods first and only use violence as a last resort.
That being said, our country is at war and we're being attacked on our own soil, so I'd be prepared, just in case, and pray that you never have to use force.