I just bought a CA compliant M&P 10 - .308 and it came with a thread protector cap and what appears to be a retaining ring at the end of the barrel. It is LEGAL in CA to have a muzzle brake, so I want to remove the thread protector(s) but cannot get them to budge. Smith & Wesson question & answer told me that they do not come off, but I find this hard to believe. Does anyone have experience removing these things?