I would HIGHLY recommend that if you weld up those barrels that you anneal the area afterwards. If you would run a series of micro-hardness tests from about 1/2" before the weld and continuing across the weld to about 1/2" past the weld you will see wide variations in hardness. This is not a good thing
to leave without annealing. A lot if welds don't fail in the weld, they fail in ductile areas directly on either side of the weld that were caused by the welding process.