HK MR556 sustained rate of fire
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  1. #1
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    Default HK MR556 sustained rate of fire

    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...
    Last edited by Chango; 07-06-2018 at 06:26 PM.

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    I really don’t bother wasting time thinking about fantasy scenarios with zombies or other such nonsense when selecting a firearm.

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    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.
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    Quote Originally Posted by dwillHK View Post
    I really don’t bother wasting time thinking about fantasy scenarios with zombies or other such nonsense when selecting a firearm.
    I was just trying to have some fun with the question.

    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.

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    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.

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    Quote Originally Posted by navyman8903 View Post
    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.
    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...

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    Quote Originally Posted by khanda View Post
    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.
    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.

    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?
    Last edited by Chango; 07-06-2018 at 08:44 PM.

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    Quote Originally Posted by Chango View Post
    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.

    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?
    As someone who’s fired the full-auto SAW on a regular basis, having the ‘S’ version would not suffice.

    Save your money and buy a real FN Minimi on the Class 3 market to get that satisfaction.

    As for the MR, you can get any full-auto knock off AR conversion built before 86, shave off the barrel extension tab and go to town.

    Remember, even a full-auto gun will melt or suffer severe barrel damage with full cyclic rate of fire at 850 rds/min. The barrel on the M249 is to be changed after one minute at the cyclic rate of fire, even with the glorious chrome-lining.

    In my opinion, if you want a machine gun experience, get a machine gun.


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    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.

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    Here is what I would do to a MR556 if I were to own one:

    1) Send it to IGF
    2) Cut the barrel to 14.5" or 14.0...whatever works for your muzzle device to get to 16"...I wouldn't worry about re profiling it unless you want it lighter.
    3) Nitride the barrel

    Now you have a good barrel that can withstand abuse a lot more than in factory form.

    Investment Grade Firearms ? Heckler and Koch Hk MR 556 416 Style Modifications, Restamps and Upgrades
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