While many quote the Gospel of Luke for the seemingly pro-gun (pro sword?) stance, all the Gospels agree that when Jesus was arrested, Peter had a sword and cut off the ear of a soldier (or struck him, in any case, the sword was there). Had the New Testament been meant to give credence to being disarmed, Peter would not have had the sword, since I'm pretty sure Jesus would have told him he doesn't need it at some point.
Yes, but ...
Matthew, Mark and Luke are called the "Synoptic Gospels" because they run basically parallel and relate the story of the ministry, trial (?) and crucifixion of Jesus in much the same way, whereas John, the fourth Gospel, doesn't run parallel to the other three at all. But it is interesting and perhaps significant that there are differences between/among the three Synoptic Gospels. This is a good example.
All three agree that one of the disciples used his sword to cut off the ear of a slave of the high priest. But they differ as to what took place immediately after.
In Luke, Jesus said, "No more of this" and healed the wounded ear. Then Jesus said his piece about "Have you come out as against a robber, with swords and clubs? ..."
In Mark, it is related that one of the disciples struck off the ear of the high priest's slave, but there is no mention of Jesus saying anything about that, or of healing the ear. Mark jumps directly to "Have you come out as against a robber, with swords and clubs to capture me? ..."
In Matthew, after relating that one of the disciples cut off the slave's ear it says that Jesus reacted by saying, "Put your sword back into its place; for all who take the sword will perish by the sword. ..." But Matthew says nothing about healing the wounded ear. Matthew then moves on to the "Have you come out as against a robber, with swords and clubs to capture me? ..." passage.
A very long time ago I took a college class in which this was discussed. I have no idea what current scholarly thinking is, but back then the theory was that one of these three (don't recall which, sorry) was written down first, and that the other two were basically copied from the first, with additions and deletions to suit the particular bias of whoever wrote them. None were first-hand accounts, because they were not written until a couple or three hundred years after the birth and death of Jesus.
Which, I guess, is a long-winded way of suggesting that it is difficult to use the New Testament to support the RKBA, because you not only have to look at each passage in context, you also have ensure that one of the other Gospels doesn't flat out contradict the passage you want to use, either in fact or in context.