First off, it isn't a question of whether we chose the AR-10 or the M14, it's a question of whether we chose the AR-10 or the T44. If the AR-10 had been chosen over the Springfield design, it would be the M14 instead, not the "M10". Also I'm not sure whether or not this was intentional, but your second drawing down looks like a Portuguese-issue AR-10 with a Hollywood suppressor on it. The actual Hollywood AR-10s examined by the Army - and the one that would have been issued if adopted - did not have the rear of the charging handle track closed off; you still had the long tail of the charging handle running outside the gun along the spine of the stock when you pull the bolt back. More subtly, a detail most people wouldn't even know about, the Hollywood rifle's gas system was on the left side of the barrel, not along the top. That change was made for the Dutch-production rifles used by Portugal and Sudan etc.
Second, I always kind of tilt my head when people insist that the original AR-10 was awesome and that the conversion to the AR-15 ruined it. The Hollywood and Dutch AR-10s were kind of pieces of junk - there were a lot of mechanical design improvements that were made just between the Dutch AI AR-10 and the Colt 601 (handguard retainer ring, spring channels, Browning-style trigger pack, different safety selector positions, snow charging handle,) never mind all the changes that eventual culminated in the final versions of the Colt 603 and 604 (M16A1 and M16, "final" meaning mid-1968 production onward. By that point we had a solidly reliable rifle on par with the AK - stop laughing please - but nothing survives making a bad first impression, thus the non-stop, vitriolic hate for the system.) You could argue that the same improvements would have been made over time if we had adopted the AR-10 in the first place, but I'm not so sure about that.
There is no doubt in mine or anyone else's mind that pushing the AR-15 into combat in 1963, fully knowing that it wasn't combat-ready and under a mountain of bureaucracy preventing any of the necessary changes being made. A lot of lives were needlessly lost in the four years it took to work out all the bugs of the design. Everyone knows the biggest thing of course is the OSD forcing the change in gunpowder but the underinformed continue to nonchalantly claim that all the problems were due to the AR's sensitivity to dirty powder, without actually realizing just how fuckin' dirty the original Winchester WC846 powder is and that - unlike with the M14 and the beloved AK - there was zero cleaning equipment being issued for it at the time. The dirt wasn't the problem though; for reasons too complicated to describe in a dA comment (this is getting long enough as-is,) the new powder ended up over-driving the system really badly; most of the reliability problems not caused by rusted-out chambers (which should have been chrome-lined in the first place and everyone knew it) were caused by the bolt simply moving too fast - the magazine spring couldn't keep up with the higher cyclic rate, the bolt was extracting too soon and either failing to extract or flat-out shredding the rims, and the rifle was just generally beating itself into pieces under unnecessarily-high impact forces. This was all fixed by increasing the total mass of the moving parts but in the mean time, until all that was figured out, the later problem was fixed simply by going overboard on materials and processes - the metal grades and heat treatment requirements for all the moving parts were bumped way up. This change was never undone after the problem was fixed the right way, and the result is unfortunately expensive but also an absolute tank. If we had simply gone with the AR-10 in 7mm, that probably never would have happened - would it make a difference? I don't know. We certainly aren't worse off for the material upgrades. Of course those changes have now been retroactively applied to the AR-10, most effectively in the current Eagle/ArmaLite AR-10A riles (they haven't cut as many corners in the name of parts compatibility with the smaller rifle as DPSM and KAC have and they are the only ones that actually use forged receivers, not billet, and the new AR-10A being where they finally stopped dicking with modified M14 magazines.)
An alternate historical evolution of the AR-10 is something I've actually explored before. I started with the Hollywood model, kept the gas system along the left side, and sunk the charging handle track into the top of the carrier (requiring a redesign of the cam pin track) so that you don't get the rat-tail running outside the rifle - a better way of doing it than the Portuguese variant, I think. 7mm (.280 British), ditched the can, gave it the AR-15-style handguard slipring and safety positions but kept the M2 Carbine style trigger pack, just beefed it up to stop sear breakage. Implemented an AR-15 style dead-blow buffer (the Big Fix from Vietnam) and went the Colt 607 route for a carbine stock. Chrome chamber, natch. The result was.... weird, but kind of awesome. I have an engineering drawing I made up for it around here somewhere, if you'd like to see it.
I talk too much. Anyway if you haven't read The Black Rifle, I highly recommend doing so.
I'm fully aware of all that. As to the name, this is for NationStates, and the person playing America in my alternate world region wanted to call it the M10. As to the rest, I'm running with the assumption that some changes would have been made to improve the weapon, similar to adaptations made when the AR-15 was developed from it. Thus, features from the Portuguese AR-10 being used, plus the Hollywood compensator that my buddy wanted on early models. Plus, I just love the look of the Portuguese.
Whoa, whoa, whoa. You're mistaking me for one of those CoD-playing fools who insists that "m15 r unrlyble and surprbad, Ak-47 4 life, #swagg". I'm fully aware that the issues with the Vietnam-16 were entirely the fault of the Army (bad ammunition, the "self-cleaning" bullshit, etc). I would argue that those improvements would have been made. And, at least for the purpose of this timeline, they have.
Sounds interesting. For the purpose of this little timeline, 7x43mm British became the NACO (North Atlantic Compact Organization) standard round, and so these M10s are in 7x43mm NACO. I'm planning on several more evolutions over time, as well.
It's nice to run into someone on this site who doesn't get all of their data from CoD and Youtube trolls. I'll certainly look into reading that, I've been meaning to for a while.
Sorry, I didn't realize this was for an alt-history game or I wouldn't have been as critical! But yes, likewise, it's nice to find other people who actually know what they are talking about - they are so rare.
Sorry if I'm just repeating more stuff you already know, but the only other comment I have is that it wasn't the Army causing the problems so much as the SecDef - Robert 'Edsel' McNamara screwing everything up as usual. He basically said "The SPIW will be perfected within four years, rendering the M14 and AR-15 and all other conventional firearms obsolete. [Hah!] Since they will be obsolete in four years anyway, let's not waste money on any further development of the weapon - just throw it into service as-is." What his civilian OSD underlings took from this was "The system is absolutely perfect the way Stoner designed it and any suggested changes to it are heresy," and then proceeded to block-wall the Army at every available opportunity and made ordering any changes to the design as slow and painful a process as possible. Then when Congress came looking a few years later for who had fumbled this program so badly, the Pentagon threw Col. Yount (the Army's appointed manager of M16 development and the one guy who was actually doing the right thing, in a constant battle with the OSD to get things fixed) under the bus. There is no justice in the world.
You should check out NationStates, we've got a thriving community of knowledgeable gun people going, and we could always use someone with extensive AR knowledge to balance out our ex-Russian soldiers, British FAL-fappers and so on.
Silly America... American small arms development during the early stages of the Cold War was truly abysmal. I will never forgive my nation for crushing the .280 British.