5.56 vs .308 for a DMR? Also what barrel length?
Try hitting up the Semi-Auto Precision forum. They might have some really good insights on this!
There has been some really good discussion about this. The main thing is how are you defining DMR? What ranges are you expecting to cover? Are you still considered a standard rifleman as well?
The 308 has a lot of ballistic advantages over 5.56. Less wind drift being a major factor. However the rifle is likely to be heavier than its 5.56 counterpart and less ammo is likely to be carried. Also with 5.56 I can bum a mag off a buddy if Im running short.
Another big question is what kind of optic are you wanting to run? A 1-4 or an ACOG will be much easier to use in run-n-gun type scenarios and CQB. However a good 2-10 or the like will be much more effective during overwatch operations.
Barrel length isnt much of a concern. The difference between a 16 inch 5.56 and a 18 or 20 inch isnt much and the shorter lighter weapon definitely has its advantages. 308 appears to be more effected when going from 20 inch to 16 than 5.56 but Im not an expert on that at all. I have seen good shooting at distance done with a 16 inch 308.
Terminal ballistics obviously the 308 has the advantage. That being said long range 5.56 bullets like M262 are pretty darn effective themselves.
Or just look into a Grendel. Ar 15 platform and lighter weight, 308 down range ballistics, no special sauce and unicorn tears required to be super accurate. They just shoot great with very little work, especially compared to similar cost AR10 rifles.
Its a no brainer to me if you reload. Many very accurate loads and bullets, Uses 7.62x39 as the parent case, one swipe through the die.
FFS, come back with a question after you’ve done some reading. There HAS been a lot of good discussion already just within this site within the last 60 days.
Oh, I thought someone had posted a note to talk
If you reload look into the 5.68 dmr. It is a 6.8spc necked down to .224. You can load 90smk, and 90 berger to magazine length. Depending on location I have seen guys claiming 2900 fps with the 90s. This is all on the ar 15 platform. With the 90’s you should be able to keep up with the Grendel no problem. The Grendel can’t use the heavy 6.5s without giving up to much case capacity.
the only drawback is that you have to hand load if you want go this route. This will probably be the next ar I build when I have the time. One of the guys working on getting this off the ground is claiming the 90 berger stays supersonic to over 1400 yards at his elevation. Which I believe was 4200’ ASL.
These days (since the latter 1970s), the Designated Marksman Rifle (DMR) is chambered in 5.56 NATO and uses the Mk262 77gr. Open Tip Match (OTM) ammo. The DMR will typically have the standard 20" barrel except in the case of the Mk12s which have 18" barrels.
Holy cow, that is nuts. My curiosity has piqued!
There is supposedly a couple similar chamberings out there, but a guy from snipershide started this version. It is a 6.8spc case with the shoulder bumped back, and the neck sized down to .224. If you can search the old snipershide, there is some info there. The member who posted about it said if anyone was interested they could contact Youngs manufacturing. The member supposedly had a lot of stuff in place or close to it. IIRC he already had reamers available, and dies were being produced. I’m not quite ready to start a new AR, but when I am this will be the way I go. I already have an spr, and the only thing I don’t like is not being able to use the magazine for the 80smk.
The 5.68dmr gives me the ability to load the 80’s, and 90’s magazine length. The 5.68dmr creator was claiming around 3100 with the 80’s.
it really depends on what you want to do
This. I’d take nothing based on 6.8 WORTHLESS. The mag issue alone isn’t worth the most magical of external ballistic numbers.
The 5.56 can reach out plenty far… but if you’re wanting to slay bodies, a 7.62 is going to be the choice. If weight/mobility is a consideration, 5.56 all the way.
Yeah, running hot-rod wilcat setups (probably heavy throat erosion on that setup) and brass just to run 80gr projectiles seems a bit…unnecessary when improved Mk262 based loads can really work well out to half a mile (and beyond in favorable conditions).
Across the pretty big range of roles that a designated marksman setup falls under, there’s a pretty wide range of what makes sense. A 12.5" Urban Recce type setup with a 1-4x optic absolutely would qualify as a candidate for a DMR setup in a fair number of circumstances - all the way out to an 18" .308 rifle that really has some legs that also fulfills a DMR type role, it really depends on expected/intended range, possibilities of barrier penetration, and weight tradeoffs/logistical considerations. Any budget/caliber, a 16" .308 setup like the SR-25 APC is ‘the’ answer. If I need interoperability with 5.56 carbines, a Mk12 (or Mk12C type setup - 16" Recce with a shorter OAL can) is the answer.
What is a Mk12C?
I’m assuming a Compact Mk12. If Mk12 is generally 18", and Mk12C is 16" then it makes sense. Don’t quote me on it though, it was just a guess
ETA: I saw a post above that mentioned a trend in DMR’s going towards 5.56 these days. I thought this was considered an SPR? So does DMR and SPR mean the same thing basically?
Mk12C isn’t a type classified anything - just borrowing nomenclature from the Mk110 and now Mk110-C which is basically the same treatment applied to the KAC sourced SR-25 based .308 precision semi-auto system.
The history of the SPR, SAM-R, Army DMR, as well as the various Recce Rifle configurations is a pretty big one, and there are some SME’s here who can provide tons more in the way of first-hand information about some of that stuff, sufficing to say that once a 5.56 AR platform is chosen for an application, tons of compromises get made based on complete cost and capability - the Marine Corps through the PWS came up with a SAM-R (20" match barreled) solution using TS30 optics (at that point the same as the SPR’s), Army and SF wound up with an 18" Mk12Mod0 early on, although units with resources and the need for more compact stuff got 16" setups (Recce rifle is the term that gets used primarily for that), but all sorts of cross-pollination started happening and the Mk12 setup that was the median compromise wound up being everywhere (2/2 and 2/8 Marines I was with had Mk12Mod1’s), so SPR has inadvertently encompassed a large swath of rifles that accomplish that mission set.
For my part, a Mk12-C would be any product improved Mod3 ‘type’ (see BCM’s Mk12Mod’3’ uppers) setup that is instead built on a 16" barrel, and uses a shorter overall length can than the OPS 12th
[FWIW] My personal example of this is an A5 system lower with GSSA, a 16" HighCaliberSales SS Match barrel and OPS 14th - the barrel drop 2", the can another 2" and loses weight overall thanks to that weight savings - the A5 system lower is simply another excellent addition, and this can work with either an SPR type optic (Leupold Mk4/TS30A2, NightForce 2.5-10x) or a Squad 1-6x optic (Leupold Mk6, VCOG, etc.), though it’s functionally just a re-imagining of what a product improved Mk12 system would be if being a bit more compact (hence Mk12-C) was the goal.
Ok. Cool concept. I was just wanting to make sure I didn’t somehow miss a service rifle being fielded. I carried the Army DMR in 2005. It worked really well as a precision rifle that emphasized on being a squad rifleman first. It was very easy to do the same tasks any other rifleman does. However being equipped with just an ACOG it made over watch operations a good bit harder.
The Mk12 is the SPR. A SPR is more geared as a sniper rifle while the DMR concept is just an enhanced rifle that gives it’s user greater range and accuracy over a standard rifleman but still let’s the user be a rifleman in the squad.
But since the Mk12 is light for a sniper rifle and uses the same mags as other riflemen it can and is used as a DMR many times.
Thanks that’s good to know; I admit I just thought that it was nothing more than the barrel length that determined the classification. I’m Glad to know there was more to it