Can a Christian Carry a Firearm?
I hope to have a more significant section on this topic soon, but please bear with what I have so far. If you are a Christian who isn't sure about whether carrying a gun is a sin or not (or if you have friends who think it is wrong), I would first point out that you should not violate your conscience; but that doesn't mean you can't look into what the Bible may or may not say on the subject (it doesn't mention firearms directly, of course). First, since there are no biblical passages that discuss the issue directly, one would have to make a pretty good case that the Bible prohibits such a practice. Second, I would suggest that you take a look at John 18:10 and note that Peter was carrying a sword with him while he was with Jesus and that he was not rebuked for carrying a sword. Instead, he was rebuked for trying to stop Jesus' arrest (which, of course, was part of God's plan). A Christian who would like to open carry should always be especially aware of how he is presenting himself; because open carrying is going to likely draw extra attention, and you do not want people getting the impression that you have a standoffish attitude (after all, we are ambassadors for Christ). Also, there may be certain situations in which it would not be prudent to open carry (i.e. if you are visiting your friend's house to share the gospel with him, or if you know it would generally offend a friend or loved one).
Although they may not be directed toward open carry folk, these articles contain some interesting perspective (Christians for Concealed Carry and Biblical Self-Defense), which you should still read critically—just because I post a link to it, doesn't mean I whole-heartedly agree (or disagree) with every word of it. In fact, here is an article from an opposing position (that I disagree with).