If i have the constitutional RIGHT to bear arms why am I having such a hard time getting an appropriate weapon?

for home defense? A little background first: I live in texas and you may or may not know this but in my state i have the right to shoot someone trespassing on my property after dark, no questions asked. The only problem is it is hard to hit someone from over 200 yards in the pitch black darkness. So i went to my local armory and asked for something with a little more stopping power than my AK-47.....something like an RPG or ideally a surface to surface missile system with night vision and infrared tracking system. sure i may end up killing the neighbors dog by mistake but i'm trying to make a point to all commie hippies who had the misfortune of wandering onto my land!!!! And they had the nerve to tell me I couldn't have that because its "illegal." So i said fine, can I at least have some anti-personnel landmines? Again, No. I want my second amendment rights dammit!!!!!!!