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HK MR556 sustained rate of fire

4K views 13 replies 7 participants last post by  Raymondpembrose 
#1 · (Edited)
Just thinking...

OK, things went South at a secret lab on Dugway Proving Grounds and zombie hoards are now closing in or millions of PLA grunts are marching towards your town in a surprise attack because the trade war turned hot and you need a crapton of firepower NOW.

Unfortunately, yesterday was a normal, zombie and/or commie-free day; the NFA was still a thing and you didn't have the ability to get into FA guns because you just couldn't justify paying the stupid-high cost of entry. "Be Prepared" is also your motto however, so your safe is already equipped with a useful, if not ideal tool for just such a crazy, unlikely situation...

I see the M27 IAR has a sustained rate of fire of 36 rounds per minute and an expected barrel life of about 15K rounds... meaning you could fire an accurate, reliable shot every 1 1/2-2 seconds until you ammo fort was entirely depleted. Given that the MR556 has such a thick barrel and no happy switch, would it be realistic to expect the same kind of performance?

I also thought about the FN M249s but I think I would rule it out as the "civvie SAW" is jimmied up to fire closed-bolt so it looses many of the real SAW's benefits while keeping the SAW's biggest negative, weight. The M249s has also reportedly been rather unreliable in the long term (although probably better than any other semi-only belt fed boutique job) thanks to the redesign to make it civilian legal.

So what do you think... could the MR556 do the job of a SAW despite the rifle's negative attributes (real or imagined)?

Also... if the MR IS capable of firing a shot every 2 seconds theoretically nonstop until it eventually turns itself into a shotgun, it would be a HUGE benefit over a "regular" AR that isn't often discussed. Hmmmm...
 
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#4 ·
I was just trying to have some fun with the question. :410:

If you need a sterile, clinical question instead:

Will the MR556 maintain a sustained rate of fire and anticipated barrel life comparable to the M27 IAR considering the barrel is not chrome-lined but is heavier than the M27, is made the same way/of the same material and will not be subject to full auto fire?

Your average chrome-lined AR barrel has a sustained rate of fire of 10-12 rds per minute. Seems the main argument against the MR is that it costs twice as much and brings nothing to the table over the rest of the AR options besides name brand panache.

Looking over the specs I suspect that isn't the case but I have no experience with the 416 platform or MR556.
 
#3 ·
I don't think anyone has run this kind of test on a MR556 before. I think a shot every 1-2 seconds would be fine through a normal combat load, but you'd have to be in a situation were you're almost overrun by a large group of people undeterred by watching others fall to your trigger presses.

I think the MR556 is best employed as a MK12 SPR replacement. It's lighter and shorter. Put a 1-8 or a 2.5-10 or some sort of magnified optic on it and you've got a deadly combination. I get where your head is at on this one, I'm just not sure there's a practical application where this would be the case. At some point you'd have to move or run out of ammo. The M27's and M38's I've seen where I'm at now, do a lot of this for sure. But the MR556 I'm not too sure about honestly. If you have more than 10 30 round mags on you, or a few drums then you might get it a bit hot and lose accuracy. I think anything over 300 rounds in a short period of time might cause issues. That's a lot of ammo btw.
 
#6 ·
I know it's not realistic save a "last stand at the Alamo" type scenario (which nobody in their right mind would ever willingly want to find themselves in) and I'm just a hobby shooter, not prepping for the apocalypse or harboring pretend soldier delusions so no issues there...

...but if I owned a Lamborghini I would probably never take it to 200+ MPH either. Still cool to know the capability is there nevertheless.

I'm intrigued by the IAR idea though, and while researching the MR vs it's .gov versions it seems everybody in the AR world loves to poo-poo the rifle because it isn't a handy sbr 416 like they want but completely ignores the possibility that the MR could "out-SAW" the actual (civilian version) SAW.

Just wondering if my hunch holds any water or not...
 
#5 ·
This is more of a question about barrel life than zombies. The OP was just trying to be funny or probably spends too much time on other gun websites with a different shooting demographic.

But as far as answering his question is concerned, it really boils down to how similar the M249S barrel is to the FN M249 machine gun barrel. If it is made of the same barrel steel and manufacturing standards, the M249S will last tens of thousands of rounds at a sustained (100 rounds/min) rate of fire. This comprises a 6-9 round burst every 4-5 seconds. The barrel change requirement according to the FM is every 10 minutes at that rate of fire, due to overheating issues.

As for the MR556A1 barrel, the testing for the M249 has probably never been conducted in the same way on the MR556A1.

The two guns were designed for two different purposes, so I would guess that it is unlikely that the MR556A1 would hold up the same. On the other hand, H&K barrel steel is world-renowned for its durability and may offer a surprise were one to test its capabilities with the M249's published sustained fire rate.
 
#7 · (Edited)
Yeah, got me there... I own a couple of clones and really love the roller-lock HKs but I'm not really an "HK guy" I suppose. I started shooting in the early 90's though so I guess I have my reasons. :420:

I completely lost interest in the MR series when it was released after I found out about the MR barrel and never gave it a fair shake... went the SCAR route for 7.62 as well.

Anyway, I find it interesting that so many new 416 derived weapons are finding success out in the war zones of the world and am wondering what I'm missing out on...

As for the SAW... I almost bought an M249s but I changed my mind when I finally woke up and realized I wasn't gonna get anywhere near actual SAW benefits/performance from a "S" despite the obscene cost of one and have heard about plenty of problems with the "striker fire" system FN cooked up to make them street-legal.

I wonder if I could fill the irrational niche in my head for a high-volume fire (for a semi gun, anyway) capable gun a la the M27 with an MR or if I'm just kidding myself?
 
#9 ·
All things considered, suppressor use not a factor, non-NFA a factor, a 14.5 or 16 inch DI system with a newer CHF FN barrel would be a much better and cheaper route to go. The lack of chrome in the MR is literally it's single downfall in the above fantasy scenario given an expectation of defending a set fighting position.

Were you to add displacement due to mass hoards and consistent fall backs to pre-prepared positions, the weight would become a factor as there would be ample off hand shooting taking place.

Were I in the given fantasy the OP gave, i'd throw down with a new URGI upper on a colt lower over an MR in a hearbeat.

That being said, had I an actual 10.5 416 in newest vented gas block version, that would be my number one choice.

An MR as it stands makes a great "Civilian" platform to create some cool guns that are "close enough" to various issue and used guns of certain specops units and will serve the typical civilian just fine as a regular shooter and fun gun. It'll even hold its own as a "go to" blaster or trunk gun for modern short term problems that won't last more then a few magazines (local LEO, i'm talking about you), but for real world work with long term use and relatively high round count engagements (let's say an SF unit stocked up on MR uppers for a deployment to Northern Iraq/Syria or Afghan) it would fail horribly and i'm not even talking about the barrel fouling issue.

The MR barrel can last for quite awhile with an appropriate firing and maintenance schedule but it's not meant to be a real blaster.
 
#10 ·
#11 ·
So I'm now a new HK owner... picked up a brand-new MR556 the other day. :biggrin:

I'm going to chase this IAR idea... (well, at least after my bank account has recovered) I'm assuming that if I wanna chase nitriding it would be better to send in a unfired barrel... might be hard to resist though!

Maybe it would be better to just accept the barrel as-is; I still can't imagine it would make any real-life difference for me, especially when I'm inevitably going to be babying this high-dollar toy.

...and if the "zombie apocalypse" were to happen, I think I'd have more pressing concerns than worrying about whether my rifling is gonna last as long as the Marine's M27.

On the plus side, my new MR doesn't have the dorky "Warning read owner's manual" lettering on the front of the lower... gets me closer to an M27 clone already!
 
#12 ·
From my experience with my MR556 - it is optimized towards accuracy, not rate of fire like the IAR. Just because it has a heavy barrel doesn't mean it is a machine gun barrel. It does handle heat well, but not being chrome lined is a major disadvantage for high ROF.

To be honest, unless you want to **** around with a bump stock or binary trigger on your HK, which most people aren't dumb enough to do, you won't be dumping as many rounds downrange as often and as quickly you think you will. Even if you're shooting dynamically and quickly at a match... reality is not fantasy.
 
#13 ·
I agree, and will never be pumping large volumes of suppressive fire downrange so it hardly matters in the real world.

Still, nice to know you could I suppose. The MR barrel is made the same way and out of the same material as HK MG barrels only even heavier and minus the chrome lining so it stands to reason that it will work the same, just wear out faster. Bear in mind I'm talking about sustained rates of fire around the M27's 36 rpm...obviously you can meltdown even a purpose-built MG after a few minutes of sustained F/A fire and the MR would would burn out even faster.
 
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