it doesn't matter what the gun is, it's how you use it. I've seen members here with photos of them competing in 3 gun with a k98 mauser.
you could just as easily train yourself to load a $235 sks with stripper clips as you could train yourself to change mags on an FAL.
as for low cost alternatives. the only gun that you listed that is cheaper than the AR15 is the SKS, now that obama gun grab 2013 just came to a screeching halt demand for 223 is going to go back down and soon after prices will fall back to pseudo-acceptable levels.
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
I never said half the stuff people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin