SR- Please keep us posted! I'd be pretty interested in seeing what others would do with an M231 clone, even in semi-only.
Honestly, I think the M231 is a fascinating evolution of the M16, but I don't see much to gain from making a semi-auto clone and trying to replicate exactly, within the letter of the law, the features of the real thing. Not that accuracy is unimportant to me, nor am I one of those guys who thinks that all M4geries are a waste because they're not select fire, but unlike the M4, which is primarily designed for semi auto fire, the M231 was adapted in such a way to make it a full auto specific weapon, which I could never make, could never afford, and would never buy at the prices that transferable examples go for.
Therefore, I'm not too concerned about having to cut down bolt carriers, and find original parts, I'd be satisified with a standard NDS lower and a short pistol style, or wire stock buffer tube, and an M16 upper, the sights can even stay, they don't do much good without the front sights anyways. The appeal for me would be the downright odd aesthetics, as well as the tacit similarity of holding this odd looking weapon that is similar enough ergonomically to the real McCoy, and tyring to stream tracers out of it on to whatever.
That being said, I'm very interested in anything anyone else can manage trying to build one of these things! Maybe someone could try and make reproductions of the gas block and handguards? Yea, dreaming again, I know. But who knows? Retro lowers certainly seems to have taken off.
~Augee