I've not seen one "plastic" buffer in a Colt, no matter what model.
The last new Colt I held (at my favorite gun shop) had, I kid you not, a black plastic buffer. It was a 20" HBAR. Its the only make I've ever seen this on.
What's weird about the pin size? Either you order large or small pins for spares or is that somehow hard to figure out?
The pin sizes on Colts have been switched around so many times, that yes, it is a pain to figure out. I want a 100% chance of getting mil-spec takedown pins on any AR I buy. Its not a major big deal... just one more thing to deal with.
Sheared carriers? I don't know what you mean by that?
They are milled so they won't be considered by the ATF as a machine gun part. Guess what so is the one in your Bushy.
The carriers in all the Colts I've held have a fully milled away bottom end... by that, I mean that the rear most part that contacts the buffer has been milled away to only a half circle. Bushy's (or mine, at least, and all that I've seen) has less of this metal cut away. The part that contacts the buffer, and part of the way inward, is a full circle. Just enough has been cut away so that it won't trip an autosear. Also, the Colt carriers I've seen don't fully enclose the firing pin. They have a deeper slant cut that exposes the rear portion. Bushy's have a more gradual cut that fully encloses the firing pin.
Now, I've HEARD that its perfectly legal to have an M-16 carrier in your AR-15, but I'm not sure about that. Maybe one of our BATF experts will step in here. If it is, I don't know why everyone doesn't just ship M-16 carriers with their guns, but thats probably another topic... I've also HEARD that the more metal you have on the carrier, the more it weighs (of course) and that weight transfers into better momentum while the carrier moves forward... translating to a reduced likelyhood of the carrier getting hung up while stripping the next round, or for whatever other reason. As to the firing pin enclosure, I've heard that if the disconnector/other lower parts fail for some reason and the hammer rides the carrier home, there is a chance of the hammer bending the firing pin if its not fully enclosed.
Note that the above advantages to the heavier carrier is stuff I read on AR15.com. If someone else wants to comment, feel free. In any event, I prefer the bushy carrier.
Listen if you want the thing to be "true milspec" buy a real M-16 otherwise your Bushy ain't milspec no matter what you think.
I didn't say it was 'mil-spec', I said it was more mill spec than your run of the mill colt. I also want chrome lined barrels and un-blocked lowers, no matter what. AFAIK, the MT6400c is the only colt currently on the table that offers both of those.
I'm not trying to insult anyone's Colts, I'm just saying that for ME, and what I look for in an AR, bushy is the best fit.