My question is, are all AR-15 magazines pretty much interchangeable, or will I later have to find a rifle to fit around my magazines?
Basically, any AR15 chambered for .223 or 5.56 will use the same magazines. Bushmasters have problems with certain lots of Orlite mags, but otherwise they should work fine with anything.
Mags to avoid include USA, National, or no-names.
Mags to buy would include:
- OKay/NHTMG/Colt (all the same with different markings)
- Other USGI mags including Parsons and Adventureline
- LaBelle/D&H/DSG Arms (all the same with different markings)
- CProducts/ARStoner (the same with different markings)
- Singapore SAR-80 mags
- Brit SA-80 mags
- Magpul Pmags
- HK
- Orlite (OK for range use, but there's a reason that Israel surplussed them off.)
Consult the magazine forum over on AR15.com.
AR15s chambered for other rounds, e.g., 7.62x39, 6.8 SPC, or 6.5 Grendel, use different mags.
Also, any recommendations on manufacturer/model for my eventual AR-15 buy?
This is quite a subject of discussion, but IMHO based on what I've read from instructors who thousands of rounds go downrange, the most trouble free AR15s are made by Colt. LMTs should be as good, based on the type of QC they do.
Slightly below the Colts or LMTs would be Bushmaster, Rock River Arms, ArmaLite, Stag, and S&W.
My AR15 is a Colt AR-15A3 Tactical Carbine, which has a 16" heavy 1:9 twist chrome lined barrel, flat top receiver, CAR handguards, and a telestock. My ideal rifle would replace the heavy tube with a lightweight 1:7 twist chromed lined barrel. The faster twist would stabilize bullets up to 77 grains. With the 1:9 twist I'm limited to about 70 grains, maybe the 75 grain Prvi Partizan loads.
I highly recommend getting a barrel with a chromed bore. It simplifies cleaning and makes the barrel much more weather resistant. They also last longer than unlined bores.
A lightweight or M4-profile barrel will shave about a pound off the rifle compared with a heavy barrel. 16" is handier than 20", but if you're primary use for the gun is target shooting that makes no difference.
Telestocks are nice because they (a) allow you to adjust length of pull for different shooters or clothing, and (b) are more compact for storage.
A flat top receiver is better for mounting optics than an A1 or A2 upper.
Check out the technical forums on AR15.com for a real wealth of information about AR15s, because I've just scratched the surface.