I would like to know if anyone has experienced any problems with mounting a metal (Alum) tri-rail lower, other than Ultimak lowers, with the Ultimak gas tube. Are their (Ultimak) lowers made larger to accommodate the uppers barrel attachment or can one use a different brand of tri-rail lower, besides a plastic one?
I like the co-witness and the none bulkiness of the Ultimak gas tube.
Thanks.