Considering picking one of these up, just to play around with. What's the best option (16" or 18") for just tooling around at the range, without optics? How expensive is the ammo?
go w/ the 16", the 2" difference at this level of rifle isn't going to make a real difference, you will gain a bit of velocity, but it makes the rifle a bit longer because you have a 18" brl + flash hider, so nearly 20" - again, not worth it. one other misconception is that people feel that the extra 2" may make the rifle more accurate - again, not at this level of weapon and by weapon i am referring to is a sub $700 ar15. i would probably pick up the 16" firearm, grab a magpul mbus (backup rear sight) for $50 and some mags - d&h industries are "us" issue for aluminum - you can find them at
www.44mag.com and also pmags - the pmags are starting to become the defacto standard for mags - they work, they are reliable and, they work and may start to become "us" issue.
in regards to ammo, you can pick up brass cased pmc for ~$310/1K which isn't too bad (considering about 6mos ago it was double that because of the obama issues) and also 55grn fmjbt (full metal jacket, boat tail) commonly known as m193 from either federal or prvi partizan - copper jacketed bullet, lead core. the problem w/ steel cased ammo is there is sometimes a lacquer coating on the case and this may cause extraction problems, but in all honesty, a firearm should fire wolf/brown bear regardless. the wolf/steel case is ~$240/1K - shoots dirtier and kind of smells bad. if you have any desire to reload, just get the brass cased stuff that is boxer primered. again, this is in case you have the desire to reload, which can bring down the price but also, if you really get into it, really tune loads to firearms for exceptional accuracy if you do your part and even becomes a hobby all into itself - even "bargain bin" rifles are probably capable of less than 1" for 5rnds @100yds in the right hands and w/the right ammo - the ar15/m16 design is a very accurate platform.
if you go a/ the 16" which i believe from what people are claiming it will have a 1:9 twist - this means that you should stay w/ ammo that has a bullet weight of 69gr or less if you want to try some of the "match" ammo - prvi partizan 69grn otm is good, cheap "match" ammo for some distance shooting - 100-300yds to see what you can - good stuff for the price. remember, when you have a 5.56 chamber, you can shoot 223 and 5.56 out of it, but not the other way around, and i am assuming from what people have said these are 5.56 chambers - again, g2g.
some places to get good prices on ammo/mags just off the top of my head:
www.44mag.com
www.aimsurplus.com
www.palmettostatearmory.com
www.wideners.com
enjoy