I've done it both ways and I prefer solder just because drilling holes in a barrel is always a bit scary to me. I once drilled right into the bore of a 15/16x.54. When I drilled, I did not use screws but pins, staked into the hole in the barrel and peened into countersunk holes in the rib. Once filed flush they are invisible.
Whatever solder you use, and low temp is OK, you'll want to tin the barrel and rib seperatly, then clamp and sweat them togather. It requires a lot of heat over a large area so the low temp may be best. Good Luck and have fun!