Okay, I'm buying my first AR and I want to do it right the first time.  Here's what I'm planning to get, and I just want some feed back to make sure it's suitable for my needs.  I'll be using it for carbine/3 gun matches, HD although it won't be a primary defensive rifle (I have a shotgun and pistol for primary HD), and possible/occasional varmint hunting.

RRA M4 Entry rifle
ARMS SIR #50
ARMS #40 BUIS
EoTech sight

I don't know much about the BUIS, some have said to get the #40L.  Any input on this purchase would be appreciated.

Thanks,
Ezterra

are you getting a forward grip?  the SIR rail isn't really worth it for just mounting optics.  i have the #46c slimline SIR.

i don't know which #40 buis i have, but i like it a lot.  comes in handy now since i forgot to turn my aimpoint off and the battery died.

what part of Idaho are located??

I plan on mounting a light, eventually, and a vertical foregrip.  Any recommendations on the foregrip?

I'm in Boise.

Edited for correction on RB Precision:

If you are planning on using this rifle for varmint hunting.... you want to get the 40L. For varmint hunting, you will need to put a scope on your rifle, and the #40L buis was specifically designed to fit underneath a scope.

As for the SIR system, it is well made, but have you thought about how much weight it will add to your rifle. It is much heavier than simply adding a Free Float tube made by LaRue, KAC, Troy or Daniels Defense. You might want to think about how much your rifle will weigh once you mount all your accessories. For varmint hunting, you will have a bi-pod, scope, rings/scope mount, plus the weight of your SIR. Your rifle will probably weight in at the 12-13 lbs. range. Thats a pretty heavy rifle to lug around.

Secondly, you said are planning on getting an RRA M4... RRA now calls it the A4 because they are afraid of being sued by colt for trademark infringement, but we'll put that aside for a second. If you do get a RRA, make sure you specifically request from RRA that your barrel be chrome lined. The Standard barrels on RRA's aren't chrome lined.... Their A4 series rifles are the only ones that they have an option for chrome lining. You have to special order this and pay extra for it, but they will do it for you.

If you buy your RRA A4 from RB Precision, they offer chroming lining of RRA A4's barrels as an option for $30.

Lastly, the RRA has a barrel twist of 1 in 9". If you plan on using this rifle for varmint hunting, you will be using bullet weights of 50 grains down to about 40 grains. For self defense, you will be using 55 grain to 62 grain bullets. The 1 in 9" twist rate will be perfect for this range of bullets;

however, for your 3 gun matches, you will not be able to use the heavier match grade bullets which weigh 69 to 77 grains. The barrels twist rate will not be fast enough to stabilize the bullets. I have heard some say they have had good success with 1 in 9" twist rate and 69 grain ammo, but the majority I've spoken with say this is not the case. I personally don't use ammo with such heavy bullets, so I can't tell you first hand. The majority of people would tell you for match grade ammo of weight 69 and 77 grains, you would need a twist rate of 1 in 7", not 1in 9". RRA does not make barrels with a 1 in 7" twist. This may have been too technical, but I was trying to give you the most complete answer I could.

Lastly I would say, that RRA rifles generally have received very high praise from people on this board, and seem to be excellent rifles.  You won't go wrong in purchasing one, but I don't think this one rifle will suit all of your intended purposes; that's ok though, almost no rifle can.  That's why you see so many ARFCOMers with multiple rifles. It just gives an excuse to buy more.

Good luck with your purchase. If you have more questions let me know.

Glockguy40

Hey GlockGuy, thanks for all that info.  It was getting a little to techy, but that's good.  I'm just getting into this, and I need to learn what I can.  I ended up ordering the rifle today from Pete at Legal Transfers (ar15sales.com), and he was great.  It is a chrome lined barrel.

As far as hunting goes, I've never actually gone out and hunted before, but I have some friends that do.  It was just a possibility, and I really can't say if I'd actually really get out and hunt with it.  Although if a whistle pig pokes its head out of a whole and he's in my field of view, I might take a shot he
I did feel an AR with a rail system up front (can't remember what kind), and it does add quite a bit of weight.  However, I wasn't too concerned because it'll be primarily a gun used for carbine matches and 3 gun matches.  And from what I've experienced so far, the COF's don't usually go more than a few minutes.  I think I can handle the weight for that long.  I have to admit though, part of the reason for the SIR is because I really like the looks of it too.

Oh yeah, here's what I ended up getting:
RRA A4 Entry Tactical w/ ARMS #40
ARMS #50
Eotech 510 (AA Batteries)
Tango Down Vertical Grip
5 30 round LaBelle magazines

Thanks again for the info!