No I don't own one (assuming you mean rifle), been shooting a number of times with cadets a number of years ago, then privately at some of the clubs after I left, been airsofting and I prefer shooting the real thing at static targets to running around firing pellets at people with masks on
Not shot an M4A1 or an American one but shot the L98 and the L85A1 (that was on an RAF base) on a range, basically the latter are the same gun basically bar the gas bits and bobs