Originally Posted by
ASH556
I've begun to describe it to folks like this:
You're buying odds. Are there folks that have Bushmasters that work? Yep. Are there folks that have Colts with issues? Yep. At the end of the day, the odds are that you are less likely to have an issue with a Colt than a Bushmaster.
In my experience and training on the issue, the things that really matter about making a gun run correctly and not give reliability issues are thus (assuming you want a fighting-grade rifle):
-Proper chamber spec, 5.56 Nato or .223 Wylde. Just because it's stamped on the barrel doesn't mean it actually is. Lots of folks putting out .223 chambers in barrels marked 5.56.
-Proper gas port sizing. For a 14.5 or 16 with carbine gas, that means .063 +/- .001. For midlength, that seems to be .07.
-Correctly installed gas key (proper screws, torque, and staking).
-Proper buffer to match gas system. Usually "H" or heavier based on the gas systems discussed above.
-Correctly installed receiver extension (torque, staking).
Other things may deviate based on personal preference and use, such as barrel twist, material, coatings. I personally tend to stick with mil-spec type things whenever possible. Whiz-bang coatings are too often mis-understood and applied incorrectly.
For my guns, I've retreated to Colt. BCM and Daniel Defense will probably be ok and run well. Markings, accessories, and manufacturing choices (DD's gas port sizing & furniture, BCM's lower receiver dimensions) have led me away from them as a first choice.
Beyond that, everyone else has shortcomings and it's tougher than ever to recommend an off-the-shelf rifle from anyone else. Noveske is a far cry from what they were prior to John's death. I've seen firsthand and worked on an alarming number of out-of-spec Noveske parts lately. Knights - probably quality, but botiquey, proprietary parts, tools, etc. LMT - non-taper-pinned FSB's, semi-auto carriers. Not a fan, especially at the price point. Build-wise, it's on par with Smith and Wesson. Again, S&W isn't horrible, but they do take some shortcuts. Only you can decide if you're willing to save $200 to cut some corners. All of the piston AR's outside of something like the HK that was actually built as a piston (PWS, LWRC, etc)....nope. Non-standard proprietary parts that bring their own issues to the table (more weight, more recoil, more parts breakage).
The absolute NOPE list:
Bushmaster
DPMS
Rock River
Diamondback
Core 15
Mossberg/ATI
Olympic
Bottom line, it's really tough to justify not buying a 6920 or 6720 for $850 and going from there with handguards, stocks, etc. That's what makes the 6920 OEM's ($750) such a great thing.