I have a Mini 14 5831 tactical, i think it is referred to as the tactical scout. Anyway, it is the model with the factory picatinny forearm rail that the factory gas block lower, screws to. When I received the rifle, the fitment between the rail and the gas block lower was poorly aligned and was tighter at the rear than it was at the front, actually contacting on the rear (toward action, away from muzzle). I have since purchased an aftermarket gas block lower which introduces a stabilizer bar. I know the bar doesn't do much for the tapered barrel, regardless it was I purchase I wanted, and the bar isn't relevant to my question. With the new gas block lower, with it being slightly taller up the sides of the barrel, it makes full contact with the OEM scout rail prior to tightening. This left me with the option of either having the end of the OEM scout rail milled down (which is beyond the capability of the glorified gun cleaners in my area), or to shim against either the top or bottom of the barrel at the gas block. the internal cutaway of the OEM scout rail is 5 sided (imagine a stop sign shaped half of a "hole") against the top of the barrel. the bottom of the barrel fits the scoop of the gas block lower and of course encapsulates the gas bushing between the barrel and gas block. other than the gas block, the OEM rail is only held to the barrel by a bolt on clip closer to the action. effectively the rail/gas-block assembly is held captive by the forearm end and the barrel detent. If I were to shim under the barrel, the shim would have to be drilled out to have the gas bushing pass through it. the barrel topside only contacts the 45 degree sides of the rail cutout. I opted to shim the top of the barrel from the rail, so to keep a square and true mating of the gas block lower to the underside of the barrel, and oddly enough the gap between the gas block lower and the rail is now square to each other, no more pinching at the rear. I made the shim from brass, a spent .270 shell casing, with short ears turned up (and one in the center folded back) to be held captive by the half-octagonal shape of the rail and held captive between the barrel detent and the rail end. My questions are: will brass sustain the temperature load from the barrel? do you see any potential faults with my prescribed solution? should i have shimmed under the barrel instead? thanks in advance for any insight.