I am not looking for cheers to either, simply some good comparisons and information. I am thinking of purchasing an M4 upper from either of these two manufacturers. I want this rifle to be suitable for field use; meaning it must be chrome lined and very close to mil-specs.  

I understand that RRA uses softer steel than BM in their barrels.  First, will this make a significant difference in the long-term performance of the barrel, both being chrome lined?

Second, are there any major differences in the upper receivers between BM and RRA in terms of quality, durability, and mil-spec tolerances?

Thanks for your input.

Hi there, Although I am certainly not the expert on both companies rifles and carbines, I have owned Atleast one from each...To the best of my knowlege, RRA bbl's are not chrome lined...they are chrome-moly...does this really make difference..? In my humble opinion... no...however, I'm sure that there are plenty of other people out that they will say YES...Again in my humble opinion, I find that the RRA stuff looks a tiny bit better...however looks aren't everything...and certainly when your life depends on it...who really cares about looks?? As for function...well, from my experience...I haven't had a problem with either. I clean my carbines frequently and shoot quality ammo..so I experience no problems. One thing to consider...Bushmaster, is the number one seller of the AR type rifle. Which can be on your side and against..if you read in the industry forums you'll see various people making comments one way or the other about them.
   Personally, I say buy the one that best fits your budget. Which ever one you get, I'm sure you'll be happy. When you do decide which way to go, email me at [email protected] and I'd love to hear what you have to say..best of luck!

I just put together two rifles, one with a RRA upper, bolt, carrier, and charging handle; the other rifle had BM parts.  As far as the uppers and charging handles, they looked the same.  The BM seemed to have better finish on the bolt and carrier.  More like the mil-spec finish.  Function seems to be equal.

I had a tuffer time getting the barrel on the RRA upper.  Whereas the barrel just slid into the BM, I had to really force it on with the RRA.  I am not sure whether that was good or bad (tighter tolerances or slightly out of spec?).

ARMS stuff works well on either rail.

Bushmaster uppers have the mil-spec dry lube.  I don't think anybody else does that.

The BM parts were about $90 more expensive, and I don't really think they were $90 better.  But if you really want a rifle "very close to mil-specs," BM is the way to go.

It is true that BM uses a harder steel in the barrels, but even a non-chrome lined barrel will last more than most guys will ever shoot their rifle.  I don't think that is a biggy.  RRA does chrome line some of their barrels now.

The RRA upper I just installed on my a BM lower has a rather long tool-chatter mark under the flip-down dust cover. It's totally cosmetic and is hidden when the dust cover is down, so no biggy. I'm just surprised 1) RRA let something like that get out and 2) a vendor would sell it to a customer! All of my BM uppers and even the no-name "FN contract" ones I've used have been cosmetically perfect.

Aside from that defect, the RRA upper has good fit and finish. BM isn't $100 better...

Quoted: The RRA upper I just installed on my a BM lower has a rather long tool-chatter mark under the flip-down dust cover. It's totally cosmetic and is hidden when the dust cover is down, so no biggy. I'm just surprised 1) RRA let something like that get out and 2) a vendor would sell it to a customer! All of my BM uppers and even the no-name "FN contract" ones I've used have been cosmetically perfect. Aside from that defect, the RRA upper has good fit and finish. BM isn't $100 better...

Same tool mark on the one I just got from Pete in NH, Makes me wonder about RRA Quality Control!

Dunno much about Bushmaster except milspec.  My 2001 RRA LEGP M4gery is flawless, though.  Wouldn't worry about steel type - they're close - heat treat's the key.  Also avail. chromed.