Well it looks like it maybe a semi auto AUG, or Galil for me. I've never seen any SIG 550 for sale other than some add. Im not paying $3-5K for something I can't feel and look at, plus mags are going to be real hard to come by at any price. The valmet's mags are hard to come by too. I know I can find mags for a AUG and Galil. What about an HK 93 or Robinson Arms 96? I know the RA uses a gas piston and has a better extractor/ ejector than the AR15. My complaint with the ar15/ m16 is after many thousands of rounds through about 6 that I've owned so far, I had one primer blow out and went under the trigger locking it up, several torn rims with and stuck cases, double feed jams and brass shavings in the ejector making it useless. Had that happen before in a 700 remington too. Those damn button ejectors. I prefer a fixed one.Now my ar15s and M4 are not jam a-matics like I might make them out to be. Often I can fire several hundred of round through each one with out any problems but over the years and many types of ammo I've had more problems out of them than say an AK47 or glock 17. I shot some 8-10K rounds out of several ak's and only had one jam. I've owned 3 glock 17's and poured 10K plus rounds between the 3 of them not a single jam. I know I can get a gas piston conversion for my AR15 but there's still the problem with the extractor/ejector. Also too, I buy what ever kind of ammo is on sale or what I can get my hands on. When the good stuff dries up like the SA battle packs did a couple of years ago then I goto wolf , heck I even used some old tarnished Isreali stuff that I found for $99 a thousand . Yeah give hell because I buy cheap ammo, but atleast Im blasting and practacing. And some times the ammo takes strange turns such as now with 7.62x39 ammo and you just have to use what you can find. I don't need a rifle that only runs on Federal and winchester.