Re: Why is Armalite so unpopular?
No matter how you define "unpopular" or "frowned upon" or "looked down upon" (your words...not mine)...the fact is that the Armalite pattern rifles are alive, well, and supported by the aftermarket with a variety of parts/accessories. As for the aftermarket support you seem to be referring to...WHY?
Receivers for Armalite AR-10 pattern rifles:
1) Armalite;
2) Eagle Arms (a division of Armalite);
3) Aero Precision;
4) Noveske N6 (the N6 is Noveske's beast now...not Armalite's with a different roll mark);
5) IRA.
In addition to the above, there are plenty of companies that offer major components for the AR-10 rifles, including the receivers listed above, barrels, etc. Many companies offer custom built rifles and uppers based on the AR-10 platform much the same way that they offer builds on the LR-308 platform. Any impressions that you have that the AR-10 is NOT being represented through aftermarket support is in error (at least where the support actually matters).
BCGs:
Well, lets see...if it ain't broke...! Seriously...why do you need an aftermarket BCG for an AR-10? (Just so you can "upgrade" if you want to?) Have you ever had an issue with a factory AR-10 BCG not working properly under any circumstances? I have run AR-10s from 12.5" SBRs to 26" target guns, both suppressed and non-suppressed, without a hiccup. They work 100% of the time, so I see no need for aftermarket crap to fix a problem that doesn't exist. Low-mass, high-speed...whatever! Do you buy everything that Mr. Marketing tells you to buy!?!?
Mags:
Well, again, I can't explain why aftermarket companies haven't jumped on the AR-10 mag bandwagon, but there are plenty of different schools of thought. One of the reasons is that the DPMS/KAC platform has gained a good bit of momentum because of the adoption of the M110 which is a KAC pattern rifle. Because of this, the "market" for fieldable magazine alternatives has been greater with companies like Magpul jumping feet first into the fray with their LR20 PMAG offering (which is a great mag BTW) to support the military's choice of semi-auto .308 platform rifles. Additionally, as new companies have come along (like DPMS, Remington, POF, etc., etc.) they have opted for the KAC pattern mags, further driving the market in that direction for mag alternatives.
This whole bitch about Armalite mags costing more, etc. is just nonsense. I don't care one bit about paying $30/mag versus $20/mag AS LONG AS THE MAG FUNCTIONS 100% when I need it to (i.e. - I didn't buy/build a semi-auto rifle only to have it reduced to a single-shot because of a "cheaper" magazine). If people are honestly going to spend $2k+ (or significantly more) on rifles, then add on optics, plus mounts, plus bipods, plus __________, ___________, ___________, then what is the BFD about paying a few dollars more per mag. Unlike some of the factory and aftermarket offerings for the DPMS/KAC pattern rifles, the Armalite mags are reliable as hell. I have owned around 50 different AR-10 mags over the years from 25rnd to 5rnd and all just plain worked without issues. However, I have had bad runs of C-Products and DPMS factory mags not functioning properly in my POF and in other KAC/DPMS-pattern rifles. That said, why don't you compare the KAC factory mags with the Armalites...you wanna talk about EXPENSIVE mags ($100+ KAC mags as oppossed to $30 Armalite mags)! I guess if you HAVE TO HAVE options other than reliable factory mags, then the AR-10 isn't for you...buy something else.
As for parts interchangeability between platforms...you can use any AR-15 ambi-selector for an AR-10, LR-308, etc. build. The parts are the same. For example, I am running one of the new B.A.D.-A.S.S. user configurable selectors in my latest AR-10 carbine build. I don't know of any compatible ambi-bolt releases or mag releases off hand for the Armalite (or any other .308 pattern rifle other than those offered from the factory from companies like POF).
Armalite versus any other .308 Semi-auto rifle:
If you want an Armalite...buy or build an Armalite. If you want something else...you guessed it...BUY OR BUILD SOMETHING ELSE. If you want to make a decision about building or buying a weapons system based solely on the mags you can use or that they cost a few bucks less or the fact that you perceive there to be more aftermarket support for your choice...go for it. If you want to continue to gripe about what you perceive as deficiencies in the aftermarket sector for the AR-10, there are a $#!Tload of folks over on BARFCOM that will gladly continue to engage in this endless debate with you. Hell, there are some geniuses there that are trying to convince Armalite to start making KAC/DPMS pattern lowers to work with Armalite pattern uppers...go figure?!?!!!!!