Okay, SDM's are not snipers, they are (were when I went through and later trained 'em at SBASC) trained infantrymen that shot 40/40 at their last two quals. with M4, 270 PT test and GT score of (I forget, but it's the same as sniper school). We took 'em for a month and trained 'em on NM competition shooting with irons, then Acog. THEN we took 'em over to UKD ranges, "sniper" ranges (ranges with cooler shit to shoot from) shoot houses, runs through Hogan's Alley type scenarios (ours were 800m and you had to run the whole thing and it was a timed event that included crawling through a tunnel and movement using smoke screen under fire). Lots and lots of fun.
The rifle was originally a stock M4 with an Acog NSN (you can in part thank us for that becoming the standard) and Harris bipod with a modified M14 sling that could be used like a NM sling. If the shooter had the time to modify the sling and didn't forget his dope, it sure helped. Oh, during the school we gave 'em M16 lowers and took their M4 lowers and locked 'em up --it's fucking hard to teach marksmanship with a loose stock. SOPMOD wasn't around yet.
Mk12 was the army's answer to what we'd been bitching about but it wasn't what we asked for. USMC had their idea of the idea DMR (which is Designated Marksman Rifle) and it's more in line with what we wanted. KAC FF rail, M16 stock, 20" match grade bbl.
In practice, army fielded everything under the sun from 5.56 to 7.62 and even 6.5. Last year Sig 716's in 6.5CM, KAC 110's and others were still in use. We tried to get M14's twenty years ago but that's another story about army fuckery (the M14's are not drawable like your M4 is --they simply couldn't figure out how to issue 'em so fuck us, M4's it was --but I bet had they dragged those motherfuckers to Mosul they'd have found a way).
Navy got ahold of the Mk12. They didn't like it. Too heavy, not accurate enough for what it is. That CF handguard is heavier than aluminum and it has another rail that goes on top of it that adds more weigh but makes it monolithic.
Navy SEAL apparently had Crane, et. al. come up with something better. They tested a bunch of shit and settled on what they call the "recce" rifle, also known as "sniper M4". It's the exact same rifle USMC and SBASC wanted but with a 16" Lilja bbl. They left the specs on 'em loose so you could choose the handguard, the optics, etc., and there are pictures of 'em in all sorts of configurations. This one is most common (not sure about the Mk4 --I think there are four variations and army, navy and marines each used a different one):
This is what I championed though:
But then Mk20 came along and changed all that IMO. Don't have a picture of mine off hand but it's got a 1-8x USO and PEQ, same Harris bipod. I honestly feel it's the best DMR option available. Army went G28, rifle was so goddamn expensive though I guess that's why they got stuck with Sig scopes? What the fuck ever, army being army. Mk20 w/6x Acog will get the job done. Mk20 is full of screws and afterthoughts and could have benefited from a folding stock but it's still the best overall option IMO. And I say Acog over LPVO due to the fact an SDM needs to be Johnny on the spot with the overwatch. No fucking with dials. If you can't do Kentucky windage and MOA math on the fly, you ain't an SDM, period.
A spotter's job is a bit different than an SDM. When an SDM gets into position, he's functioning a lot like a sniper and spotter combined, otherwise he's a doorkicker. He has relatively low need for camo and his movement is usually covered by a platoon size element or larger --he ain't on his own. Less comms, more ammo. But there are times the roles reverse.
SDM's IME get more range time. It was common for snipers to go through our course if possible --I mean, we had the ranges. It was common for snipers to share our ranges and more than a few times SF guys would lend a hand and we'd share our range. We used Bde. snipers from all units as instructors. SDM's were trained in spotter/shooter teams so they know how that works. Each pair had a sniper assigned to them to call shots and monitor the shooters. Now big army took our school from us in 2004 and fucked it up and I don't know what they do at Benning now but I do know it's only half the course.
It's always been an interesting discussion for sure. IME SDM's got more range time, thus what attracted the snipers to the course (it was fun, trust me). And once you were an SDM, you were allowed to draw you rifle and bring it to any range we had running provided your COC didn't give a shit. This wasn't used as much as it should have. Snipers got the stalking training, SDM's didn't. Hell, I always wanted to be a sniper until I got into SDM shit! And there was a point when they were considering making up a tab for SDM's much like snipers --but since snipers are sometimes treated like spies in the field it was figured why bother, because even though it's stupid to wear a sniper tab on a deployment uniform, there were still guys that sewed that tab under their pocket flaps. Stupid. One less thing to worry about. Having some kind of designation on your DD214 would have been nice though.
We were so old school and under the radar we had our own uniform, didn't wear rank or go by it (you could say we traded our military bearing for pure warrior attitude) brought our own shit to the ranges, pissed off lots of brass. But we were the Bde. CO's pets and we performed. We also ran pre-ranger and pre-sniper course as well as teaching butter bars how to actually shoot their pistols. For going through West Point, they somehow all developed "Glock fingers" or so we were to believe because they couldn't hit shit with an M9. FWIW, I was the only instructor that hadn't been to a formal sniper school. So that should tell you right there where it all comes from and how it was developed.
IMHO, the school was really only to hone those that were already good shooters, teach 'em a few tricks, get 'em on point with an optic, but the most important thing we did was to introduce them to their rifle for the first time regardless of how many times they shot it, what it's capable of to it's limit, and absolute top of the list? To provide dope on their rifle and a confidence in how it shoots to the limits of capabilities.
Which for 5.56 out of a 14.5" bbl. will be right at 600m w/M855. I set up 800m and 1k targets for the 7.62's we brought from home to play with and I'd try 'em with the M4 but best I never got useable dope --do your best it still goes trans somewhere around 700 and restabilizes to a new trajectory that isn't what you planned on and it can literally go over, in front of or to either side of the target. Ie, it's useless past 600m.
AND I've been downrange while they were shooting... Yeah, I know, don't need to hear it. Anyway, that "SNAP!!!" starts to go away at 600 and that oughta tell you something too. Which is that if 5.56 is fine for 600m, then .22lr if fine for door kicking --and it ain't. Trend was towards 6.5CM but I guess HK's dick don't get hard for that so G28's only come in 7.62 I understand so we're back to that.
Man, don't drag me into an SDM discussion, I got shit to do!