I'm looking to buy a tight fitting upper receiver with an M4 extension to put onto my LMT defender lower. I'm looking to build an accurate rifle for target shooting.

Besides the obvious of choosing Colt or LMT, I was wondering if their are other names out there that will work fine. I was surprised to see that both my Colt complete uppers fit onto my LMT lower very tight, but my RRA complete National Match upper fits onto the LMT loose. Any advice or input about LAR, Cardinal Forge, Stag, YHM, Bushmaster, High Standard, or other names?  I might find a tight fitting receiver that I know nothing about only to find out later that I bought a tight fitting POS.

BCM, Spikes, RRA, LT . . .  lots of choices.

Just remember that "tight fit" doesn't mean anything as far as the quality of the upper receiver, nor does it affect accuracy. I like to have "tight" rifles myself, but I know that it doesn't matter if it isn't tight from a functional standpoint.





In today's market there's really no good reason to buy anything less than a Spike's or Bravo Company Manufacturing. They are so cheap now that you barely pay more for the high quality parts and good quality control. Colt, Daniel Defense, and LMT are also quality choice but will generally cost more for just the upper.
 

Model 1 Sales upper is the tightest upper that I've encountered.

Although I agree with comments in prior posts on loose fit does not equal bad QC, if you are concern now, you will be later.  It will probably drive you nutz if at all anal about it.  If you have some uppers that fit, stick with those MF.

You may want to try to find out who else are in the same MF bucket as the ones you have now that fit tight.  There was a thread on here somewhere that listed out MF under same forging buckets for lowers, not sure if one exists for uppers though (just a thought).

My experience has been that RRA machines its receivers to fit as snug as anyone out there. I've seen others from time to time that are also this tight but seldom see anything that isn't tight from RockRiver.

The OP disagrees. Did you read the opening post?

The funny thing is, that my RRA upper and lower receiver on my National Match rifle fit so tight, that I had to use a wooden dowel punch on the pin to open the rifle. BUT.....when I bought a complete LMT Defender lower and put that same RRA national match upper onto the LMT lowr, the fit was as loose as a goose in a Gay Day Parade in SanFran. Yet, I can put my Colt 6721 or Colt 6920 uppers on that same LMT defender lower and they fit super tight.

Anyway, I'm going to take the LMT defender lower with me to the gunshow to try fit- whatever AR upper I find  and make sure it fits together tight. I was just wondering which name uppers to buy and avoid, as I also don't want to make the mistake of buying something that fits tight, only to find out later that I bought a tight fitting POS. A perfect example of what I'm talking about is the DPMS for example;  I've heard enough about their 5.56 stuff to know to keep away from it.

I don't profess to know about all the names out there including Stag, Bushmaster, LAR, YHM,Cardinal Forge, High Standard, etc. You know.....a lot of companies also put their own name on somebody elses stuff too. Like BCM........they don't make their own parts, they just sell it under their own name. Just like Denny puts his global Tactical name on Stag.  If you guys didn't say BCM was great stuff, I'd not know it. (I still have no clue who manufactures BCM's receivers).