1. Manufacturer: My understanding is that Bushmaster is the best bet. The only other ones I would consider are Rock River and DPMS. Go Bushmaster?
You would be pleased with any one of those rifles. Each one makes a quality product. The ONLY think I'd say is that if you go Bushmaster, and the rifle you want needs to be ordered, be careful as certain rifle types might take some time to get in (some at minimum 6-8 weeks delivery)
2. Barrel length: I believe that what makes these guns effective is their velocity, so isn't a 20" barrel better than a 16" (or 14.5") barrel? How big a deal is this?
That, and generally the better sight profile, as the front post is further away on the 20". It really only gets to be a big deal depending on application. If you're just plinking at 50-100 yards...the difference will be minimal. If we're talking 'hog hunting at 400 yards....the 20 would serve you better.
3. A2 vs. A3: I don't understand what the difference is, nor have I read any reason why the A3 is better. Are there any important differences?
Yup. A2 = fixed handle. A3 = detachable handle. A3 gives you more options for mounting optics, since removing the handle gives you a rail on the upper to mount just about any optics you want. Not a big deal, but mounting a 10x scope for distance shots on the carry handle won't be fun....
4. M4: Seems like the M4 is the rage these days, but how well does the short barrel perform?
Depends. This is actually something that gets me. I know a lot of people who say they get 1 MOA, and sometimes even less, out of a 16" barrel. They do....but sometimes forget to mention that that's with a free floated barrel, match quality ammo, optics, and off of a bipod or sandbags. Much different when shooting offhand, with factory loads and no freefloat. I'd say, offhand, and I'm not a very good shot.....I can keep the hits on torso pretty easily at 100, with only an aimpoint or iron sights. At 200 it opens up pretty wide though, offhand. A better shot I have no doubt could keep it in the 2 MOA area at 100.
Basically, I'd say this. Decide what distances you're going to shoot, what targets you want to shoot, and what optics you might want to employ. THAT will go a long way in telling you what would be the config to best fit your needs. Personally, I like the 16"...it's a nice compromise of accurcay and size...lightweight and easy to carry with mounted optics. But I wouldn't use it past 200 yards or so.
BE WARNED - this could lead to an afflicting and debilitating disease. I got my first AR, a Bushmaster 16" M4, a few months ago. I'm now saving for a new upper, and planning on building an SPR. They are VERY addicting to shoot!
I'm looking for something I can do some informal target shooting with at the range but also use on Wiley Coyote at out to 275 yards or so. After looking at all the oferings on the internet, I'm leaning toward the RRA varmint flattop version with a 20" Wilson air gauge barrel. They claim 3/4" MOA. I could throw my Leopold 4 X 12 on it for hunting and install the detachable carry handle/ rear site and detachable front site for plinking. The list price with out the detachable sights iis $950 on RRA's site. Anyone know what the "street price" should be? Is this a good rifle? Thanks
Good rifle? Definitely. Haven't heard of any probs with their varminter. I use their 2 stage trigger (which the varminter has), and it's an EXCELLENT trigger. The 1/8 twist of the barrel will help you with the heavier bullets, which I think you'd want to use on the 'varmint cong'. As to what the street price is...probably not much difference, depending on local. I've seen them go as low as $850, and as high as $1000. There's a dealer on AR15.com, Pete from Legal Transfers, big RRA dealer....has great prices and he could probably hook you up with one of the 'US Property' marked RRA lowers for it. I've dealt with him before, and the service and prices are hard to beat.