As long as the lower is marked as a pistol, you can use any length upper but you can't turn it into a rifle with a stock.
There is no requirement that a lower has to be marked as a pistol to be built as a pistol...
I'm currently looking to put an AR15 pistol together and I'm not familiar with laws and regulations when it comes to pistols, can I use an upper with 12.5 inch barrel and brace and still legal?
They have been out for a few years now. There are some other ones out there too.I've never seen those folding buffer tubes are those a new thing?
So I'm in the prosess of building an AR pistol and I'm haveing a hard time deciding weather to go with a 10.5 upper or a 14.5 upper. Any suggestions on which length to go with? Also I really don't know what manufacturer to go with either. I don't really want to spend more than 600 on the complete upper. Does anyone know of anything that fits that criteria?