"Excuse me, but I must remind you the AR is a “rotating” design as it has a rotating bolt. It is certainly not “funky”."
Look at point #2. I said the barrel extension
specifically has swept the world over in almost every design case, but the gas tube/key/carrier piston thing has not. The pressurizing of the bolt carrier is undeniably an uncommon (i.e. 'funky') characteristic when practically every other design that's been implemented for any length of time uses external force to drive the carrier back.
"I challenge you to find one post-WWII service rifle design that has been developed to do as many things as well as the AR system. It will not be the M14, FAL, AK, G3, FAMAS, STG57, Enfield or AUG."
Example;
AK dual-lug rotating long/short stroke action. Aside from being the basis of the majority of service rifles for the last century, it has been applied to everything from pistols to belt fed heavy machine guns. Two large lugs require the barrel trunnion area be larger than can be obtained with a Stoner-type lug ring, but tolerances
can be a bit looser and construction with machine tools easier. M1 Garand lands solidly here, as does the AR70/SIG550, and even the HK MP7 if you'll 'permit' me to include it by way of it's G36-esque gas system (but AR-style multilug bolt head). IIRC, even the M249 called in to do what the M4 can't uses this system (though is hardly the best execution of it)
BREN rear tilting bolt long stroke action. Again, applied to everything from rifles to heavy belt fed machine guns and anti-tank rifles, numerous variations for different roles, numerous nations arriving at the same solution (Goryunov, for example). Killed due to the need for beefed up long receivers to carry lug load from the rear of the bolt to the barrel trunnion. I suppose you could lump the FAL/FN49/SKS in this category if you look broadly enough.
G3 roller delay. Applied to everything from 9mm MP5s and the PSG1, to the belt fed Amile by CETME. Adopted/developed/stolen by many nations like Switzerland (STGW57, which turned out to be a very nice shooter today
). Killed by weight required to retard the bolt, even in spite of it being delayed, and by poor design choices by the trail blazing designers at CETME and H&K who made the design much more complicated and unmodifiable than it needed to be. I think history has also shown these designs were also less user friendly than they really needed to be (never get in a thumb wrestling match with a Franco-era Spaniard, German vet, or Swiss reservist)
VZ58 pivoting locking piece. Applied to the VZ58 rifle in x39 and the belt fed x54r UK59. Unique to Czech designs, despite being fixing entirely the shortcomings of a rear tilting bolt system when it comes to receiver complexity, size, and weight. The platforms it's been tried on used expensive machined receivers in Czech tradition rather than cheaper forged trunnions or barrel extensions, which probably is why it hasn't caught on (though the design itself does not require this production method). Alas, I think this action was doomed by bad timing; the late fifties being the time when post war Europe, USSR, and the US had already chosen their infantry arms for the foreseeable future and had no interest in novelty.
Degtyarov. My personal favorite at the moment
. RPD (x39), DP28/DPM (x54r), DShK (12.7x108mm), and I think there's an even bigger 20mm or grenade launcher out there, too. I'm adapting it the opposite direction for a 7.62x25 carbine. It flares out two flaps on either side of the bolt into receiver recesses. Brilliantly simple, safe, reliable, and easy to make, but has the same receiver-design shortcomings as the tilt bolt setups with their heavy machined parts.
Direct gas impingement. AG-42/Hakim/Rasheed, AR15, MAS49/56 (I think). And I think the AR is unique among them about pressuring the interior of the bolt (I'm honestly not that familiar with these obscure guns, though). Aside from the American development, which had the whole weight of our military complex thrown behind it for 50 straight years, didn't become particularly popular until quite recently when the Euros made their last equipment upgrade (late 80's/90's through the present). A lot of it's increased stature internationally can be explained by the fact it was front and center in two large scale wars for a decade straight, and performed well, which helped increase its market share independent of its excellent record. More though, it is explained by the M4 variant which was demonstrably smaller/lighter than competing platforms at the time. Now that the merits and deficiencies of the M4 are better understood, newer designs seek to capitalize on the compact size and lightweight modularity, while not sacrificing sustained firepower capabilities and (supposedly) increased maintenance (though that's what they back in the 60's about the AR itself
)
I ain't talkin' smack about your, or any, ARs. This is merely my observation from learning about the operational details of a ton of different platforms both successful and unsuccessful throughout history. Similar to how a roller-locked recoil operated pistol is fairly uncommon in history, so is a rifle which unlocks the bolt via internal pressure. And if the latest crop of designs being pitched is any indication, it will not become
increasingly popular in from-scratch design efforts. That was the entirety of my statement.
"Most of the post-WWII designs have been replaced or reached a development and modification point of diminishing returns."
I wouldn't argue the AR design is evolving by 'leaps and bounds' these days either, but then again, no one is
. I also don't happen to see the AR as being nearly as modular as many make it out to be, which may color my perception of its ongoing 'development' differently (i.e. a 50cal, 5.7x28, pistol blowback, or piston upper are not outgrowths of the AR design in my eyes, but rather independent ideas shoehorned to fit an existing form for better marketing)
TCB
*"The only other military machine I can immediately think of that has demonstrated a design that has outstanding inherent ability for improvement and modification to do so many things well is the Supermarine Spitfire."
I'm afraid you'll have to elaborate (if you care to). I know they stopped making them with the more efficient elliptical wings early on due to production difficulties, but that's the extent of my Spitfire configuration history knowledge