After bead blasting my receiver/shroud assembly, I used a can of automotive brake cleaner to rinse out the inside surfaces. They come with a plastic nozzle to get into the "nooks and cranies" and it worked pretty well for me. It strips all the oil and grease off due to the chemical content, but anyone who has ever done their own brake job knows how well this stuff cleans. Just be sure to wipe everything down with an oily rag when you're done. Works pretty well on the barrel bore and chamber too.