@Johny_Baba and others, how feasible is it for Sig Sauer to make a DI version of the SIG MCX,
like how they made the SIG 716i from SIG 716G2? Considering it’s SBR variant was one of the few carbines that could fit IA’s 5.56x45 CQB Carbine requirements (as if I’m not mistaken the RFI called for a folding and adjustable stock, though this is disputed by some members, but there’s no way to clarify now as it’s no longer visible in the IA website), buts is US Civil market MSRP of $2200-2300 is clearly a little out of the army’s budget due to its short stroke gas piston design. A DI version should be inherently cheaper and might be affordable to the Army if Sig was willing to do so right?
you mean a DI MCX-ish-AR-15 with folding buttstock ?
easy peasy but it would kinda imbalance centre of mass (or is it called centre of gravity ?) on AR design (one reason AK ;muzzle climbs; a lot is because a relatively heavy bolt carrier moves violantly back and forth inside a lightweight, hollow receiver; in general true for other designs too in their respective ways)
the ;most near; thing to this design existed in something named
LR-300 rifle from a designer named Allan 'Al' Zita,
the principle idea behind this design was to eliminate the opening of gas port between gas tube and gas key that occurs in AR design when it cycles, leaving out much unburnt carbon residue inside the receiver itself etc,
so Zita just played reverse uno card and lengthened gas key and shortened gas tube, shifting the overlapping of both outside receiver and above barrel, while at same time also shifted recoil spring system at front, on the gas key itself,
this new gas system that he named "delayed impingement" and this arrangement also removed necessity of recoil spring system behind bolt carrier so he could ;shorten; it there (practically he just cut bolt carrier in half, leaving only necessray front part)
end result = this
which also gave this folding+adjustable length buttstock of his own design, but any modern AR style buttstock could be thrown on it
also, change in trigger group since rear side of the bolt carrier hits on auto sear etc, elimination of that part required something new and Zita simply adopted an AK-auto sear like lever arrangement that would be actuated by AK-type auto sear cut on the receiver and it would further actuate AR style auto-sear etc...
So did it work ?
yes
then why didn't it got much success ?
because Al Zita was perhaps "too early", what i'm saying is he designed and started manufacturing it-selling it on small scale in early 2000s, back then gun market in the US was passing through a stagnation with not much on offer to consumers and their 'needs' were mostly covered by already prevalent AR style firearms so why bother with a new 'fancy' design ?
later Zita sold off this design to certain Para Ordnance that relaunched this rifle with picatiny rails and stuff with new tag but again, faced same fate,
from here it is said that design further was sold to some new company that decided not to manufacture it and kept sitting on it without doing anything, from there Zita got his original design back (i.e. got rights over it) and....he also is mostly doing same ? not doing much with it ?
anyway just saying what you're asking is indeed possible and there existed one working design that shown ;proof of concept; of such idea (albeit with slightly different gas system and recoil system etc but still)...so yeah
in case of SIG MCX, doing what
@Lonewarrior mentioned in some clever engineering way would be the way to bring DI pattern gas system for MCX design
BTW another sidenote, just as this topic is brought,
very early Armalite AR-12 design i.e. 7.62 NATO rifle that Stoner started working on after AR-10,
this rifle also was practically going to become a DI gas system rifle with wrapped recoil springs around bolt carrier thus giving a design that could easily be adopted for folding stock variant etc; the main idea behind the design was to make a stamped sheet receiver design for ease of manufacturing etc,
later when AR-15 was sold to Colt, stoner switched from DI to his own short stroke gas piston system on this AR-12 and further it became AR-16 (NOT TO BE CONFUSED WITH ANY M16) and later scaled down version of AR-16 became AR-18 etc...
It is said that Stoner just dropped idea of utilising DI gas system after those vietnam era issues started bugging his mind and of course he lost design to Colt and so, otherwise who knows even AR-18 could have been a DI like rifle...but chalo jo hua achcha hua with that we at least have this huge family of AR-18 derivatives that comprises of short-stroke gas piston system rifles with stoner-pattern multi-lug rotating bolt system...