I a little hesitant to try to fit firearms ownership into Scripture.
But a few points MUST be noted.
1. Jesus was NOT a pacifist. His only point when He told Peter to put His sword away at the crucifixion was that the Kingdom of God was NOT to be advanced in the same manner that the Muslim kingdom was during the first millennium - namely, by force.
2. The Luke text is prophetic. But there is NO WAY to know WHAT period of time it refers to. it behooves the wise man to make preparations early, which IS a Scriptural teaching.
3. NOTHING in Scripture prohibits Christian from owning weapons. Anyone who says otherwise is spreading false teaching. The israelites DID NOT come to inhabit the promised land by simply asking the heathens to leave - they founght and took it, by God's command to do so.
4. The freedom to worship God was WON by means of arms. I DO NOT see anything unScriptural about the existence of America. If freedom was won with arms and by God's help (and it was) then it is my responsibility to maintain freedom in that manner.
I bookmarked that site. Seems like there is alot of good info there. They even use the AR15 to illustrate some marksmanship techniques.