HKPRO Forums banner

1 - 20 of 59 Posts

·
Registered
Joined
·
590 Posts
Discussion Starter #1
I am going to buy a HK piston AR with a 10.4" barrel just like the HK416. The 2 routes I know to go are:

1. Buy the HK MR556 rifle and get the 16.5" barrel cut down to 10.4 inches, re-profiled and rethreaded by a qualified gunsmith.(IGF) Mod or replace the gas block with the HK 416 gas block. = $2,800

2. Buy a HK 416 10.4" upper and put it on a HK MR556 lower. = $4,750-$5,250


These will never go full auto with me, so the full auto BCG in the 416 does not affect my decision. My question is besides the chrome lined barrel in the 416, what will be the difference in the 2 above weapons? Is the threading on the barrel different on the 416 & MR556?

Thanks in advance for any help.
 

·
Banned
Joined
·
879 Posts
I'd say get the MR556 and have the barrel QPQ nitrided while it's off for the cutback/reprofile.

You'll end up with an extremely durable barrel, probably more-so then the chrome lined 416 given all the data i've seen about nitriding, and it'll still come in way less then a 416 upper.

For what it's worth, when I removed my MR556 barrel for the re-profile and cut back to 14.5 inches, I also removed the nub on the barrel extension so that if I ever have the opportunity to run this with an FA carrier (if HKparts.net ever gets them in stock and I go shooting with one of my NFA dealer buddies), I will be able to.

IMHO, my MR556 will actually be "better" then any 416 when it's complete. Reasons are that it will have a match chamber, nitrided inside and out, and I'll even have the bolt and carrier nitrided as well. Yes, Chrome is good, but it is an imprecise process by its very nature and while it does an "ok" job at protecting (I say ok because it's actually pretty porous all things considered, it can affect accuracy. With a nitrided MR556, you get all the benifits of the match grade barrel, a barrel treatment "process" (it's a metal treatment process, not a coating) that penetrates the outer surface of the steel to twice the depth as chrome is thick in a typical rifle barrel (about the same depth though as an FN CHF barrel as manufactured for Noveske, Centurion, etc), but has far greater corrosion resistance features and is just about as hard as chrome but doesn't have porousity issues nor does it stand a chance of flaking off as Chrome may as time goes by (yes, chrome flaking is relativly rare, but it does happen). On top of that, Nitriding happens to the entire barrel, both insode and out, so care and maintinence is much easier all the way around.

Insofar as your question regarding barrel threads, both the MR556 and the 416 are threaded 1/2x28 for the flash hider(standard threading for 5.56mm guns), and if you go the MR556 route and have it cut back, the threads will be the same.
 

·
Registered
Joined
·
590 Posts
Discussion Starter #3
Thanks for the input, the MR556 conversion sounds like the way to go especially since I have no plans to go full auto in this gun any time soon, if ever. It is almost half the price of going the 416 route with almost identical uppers, besides full auto BCG of course.

Have there been any pics of HK MR556 Form 1 engraved lowers on this site yet? The lower is already cluttered with white printed words....
 

·
Banned
Joined
·
879 Posts
There's plenty of room for engraving on an MR556 lower. If you want it generally unseen, but easy to find, i'd say have the markings engraved on the inside of the trigger cut out so you can only read it when the gun is literally upside down. That is if you can find someone with the ability to engrave in such an area.
 

·
Registered
Joined
·
590 Posts
Discussion Starter #5
I will talk to IGF and hopefully they will be able to do the engraving or know some one that can do a good job for me. It is just a small engraving but could really screw up the look of the rifle if done improperly.

I was not going to get the barrel reprofiled under the hand guard at first but now I am changing my mind. I may get the mid-weight profile, since the barrel will be off already anyways. It should be much lighter after taking 6 inches off that beefy barrel.
 

·
Banned
Joined
·
879 Posts
I will talk to IGF and hopefully they will be able to do the engraving or know some one that can do a good job for me. It is just a small engraving but could really screw up the look of the rifle if done improperly.

I was not going to get the barrel reprofiled under the hand guard at first but now I am changing my mind. I may get the mid-weight profile, since the barrel will be off already anyways. It should be much lighter after taking 6 inches off that beefy barrel.
I cut my MR556 barrel to 14.5 and took the barrel under the handguard to .7 inch and I am VERY happy with the new weight and resulting balance shift of the rifle. I also added an 11 inch M27 rail which added a little extra weight and the addition of a surefire X300 light, rail panels and a TD stubby VFG added even more, it's still less weight then the gun was naked with the full sized barrel.

The damn thing points like a dream now.
 

·
Banned
Joined
·
879 Posts
It's going out for QPQ on the next paycheck here in a week or so.

Parts being processed will be the barrel, gas block, barrel nut, bolt, and carrier.
 

·
Registered
Joined
·
675 Posts
Good thread. Bought a MR556 lower engraved by a company and registered with ATF they are waiting on some kind of license before they can send it to my class 3 dealer . Been three months now.
 

·
Registered
Joined
·
133 Posts
So long story short, once you reprofile and shorten the bbl (and weld the gas port) the guns are in all essence the same?
 

·
H&K Certified Armorer
Joined
·
8,216 Posts
Note that when you Nitride a barrel, you add a degree of brittleness to it. The German CHF process in conjunction with the material they use allows for the barrel to evenly bulge rather than split or even fragment in the event of a squib. Adding treatment options to the steel may adversely affect those features that the German barrels are known for.
 

·
Registered
Joined
·
590 Posts
Discussion Starter #13
So long story short, once you reprofile and shorten the bbl (and weld the gas port) the guns are in all essence the same?
Very close but not exactly, the 416 has a full auto BCG which differs from the MR556. The MR 556 barrel also has a extra nub piece at the receiver that prevents one from running the full auto 416 BCG in the MR 556. The 416 gas block has sling loops and a grenade launcher attatchment.

And the most controversial part, on other gun forums, the HK 416 has a chrome lined barrel and the HK MR 556 does not.
 

·
Banned
Joined
·
879 Posts
Note that when you Nitride a barrel, you add a degree of brittleness to it. The German CHF process in conjunction with the material they use allows for the barrel to evenly bulge rather than split or even fragment in the event of a squib. Adding treatment options to the steel may adversely affect those features that the German barrels are known for.
Nitriding penetrates to depths between 0.008" and 0.040". The substrate retains all original properties and will perform as intended.

I do believe that the Sig 550 series is designed to handle similar situations and is nitrided.
 

·
H&K Certified Armorer
Joined
·
8,216 Posts
Also, HK puts the has hole in the grove of the rifling to reduce the affect on the bullet. When you move the gas block you loose that unless the smith can find a way to drill the new hole in a rifling groove.

They have a split SIG barrel at the range I go to.
 

·
Banned
Joined
·
879 Posts
Also, HK puts the has hole in the grove of the rifling to reduce the affect on the bullet. When you move the gas block you loose that unless the smith can find a way to drill the new hole in a rifling groove.
What exactly are you talking about?

Nobody has discussed moving the location of the gas block that i'm aware of.

Secondly, the location of the gas port is a function of the headspacing as caused by the barrel extension. Gas port is drilled AFTER the barrel extension is properly indexed and if the gas port happens to fall perfectly on a land or a groove, then fine, if not, oh well. That's simply the way AR style barrels are manufactured. Getting every single barrel and barrel extension to line up according to a pre-drilled gas port would be so time and resource intensive that no company would even attempt it.

That being said, I fail to see how a gas port drilled into a land vs. a groove will behave any differently especially considering the typical gas port erosion patterns.

They have a split SIG barrel at the range I go to.
And this means what? Nothing unless you provide some context to go along with it.

I've seen an Accuracy International sniper rifle that looked like bugs bunny stuck his finger in the muzzle when it was shot. Doesn't mean that the barrel is a piece of crap, it means that any piece of machinery or equipment can be used excessivly or abused past their abilities.
 

·
H&K Certified Armorer
Joined
·
8,216 Posts
I can not comment on the findings of another company or entity. I can however comment on the findings of Hk's R&D. And yes, they indeed do index the barrel in order to get the gas block hole directly in a grove. And they do believe that it helps, to some degree, to improve accuracy. They have done that dating back to the G36. Someone earlier had mention reposition the gas block which is why I brought it up. HK firearms are expensive for a reason. The effort required to do this is one of them.



What exactly are you talking about?

Nobody has discussed moving the location of the gas block that i'm aware of.

Secondly, the location of the gas port is a function of the headspacing as caused by the barrel extension. Gas port is drilled AFTER the barrel extension is properly indexed and if the gas port happens to fall perfectly on a land or a groove, then fine, if not, oh well. That's simply the way AR style barrels are manufactured. Getting every single barrel and barrel extension to line up according to a pre-drilled gas port would be so time and resource intensive that no company would even attempt it.

That being said, I fail to see how a gas port drilled into a land vs. a groove will behave any differently especially considering the typical gas port erosion patterns.



And this means what? Nothing unless you provide some context to go along with it.

I've seen an Accuracy International sniper rifle that looked like bugs bunny stuck his finger in the muzzle when it was shot. Doesn't mean that the barrel is a piece of crap, it means that any piece of machinery or equipment can be used excessivly or abused past their abilities.
 

·
Banned
Joined
·
879 Posts
I can not comment on the findings of another company or entity. I can however comment on the findings of Hk's R&D. And yes, they indeed do index the barrel in order to get the gas block hole directly in a grove. And they do believe that it helps, to some degree, to improve accuracy. They have done that dating back to the G36. Someone earlier had mention reposition the gas block which is why I brought it up. HK firearms are expensive for a reason. The effort required to do this is one of them.
Going this extra step on a G36 barrel is a far less intensive process as the G36 headspace is set by the barrels attachment to the receiver.

Do you have a link to an explination by HK that they in fact perform this process on their barrels? Perhaps a scanned letter from them?
 

·
Banned
Joined
·
879 Posts
I can definitely see how an irregularity (gas hole) on the land instead of the groove could affect accuracy.
How?


For the record, there has been no studies done (that I know of) of barrels with gas port vs. barrels without gas port regarding accuracy.

Nobody has taken a match grade barrel, chucked it up in a ransom rest, fired for accuracy, then drilled a port in the barrel and re-tested to see if there was a change in accuracy potential.

Until this is done, the effects of the gas port are theoretical. Given all the stresses already imparted on a bullet during the fireing of a gun, I doubt that a small hole in the barrel will make that much of a difference. And even if it did, the effects of a self reciprocating action, the addition of extra weight on the barrel by the gas block, the cycling of the piston, bolt and carrier have a far worse effect on the accuracy of the system to the point that any theoretical damage to accuracy done by a gas port is a completely moot point, and vurtually impossible to prove. Matter of fact, of all the recovered bullets i've ever seen, I've never found any mark anywhere on the jacket that indicated that the gas port had any effect on it such as marring it or causing deformation.

I'll be more then happy to be a test bed. All HK has to do is send me two MR556 uppers. One that has the barrel completely profiled with the exception of having a gas port drilled, but has the location marked with a dimple and has it located so that when drilled it will be directly in a groove, and another with the barrel that is completely profiled with the exception of the gas port and it will be dimpled where the gas port is supposed to be except that it isn't indexed to drill perfectly into a groove.

I'll install each upper seperatly with a lower, match trigger and an accu-wedge to remove as much play from the uppers and lowers as possible, then mount in a rest, follow an exact "break in" procedure then fire several groups without a gas port and no gas block installed (basically a bolt action rifle), then take the barrels to the machine shop and drill the gas ports, de-burr, then head back out to the range and repeat the process (still with no gas block installed). Finally i'll install the gas block and op-rod and shoot several final groups and compare results. Ammunition will be used all from a single manufacturer and from the exact same lot to ensure consistency.

My guess is that there wouldn't be a discernable difference between ported and non-ported until the gas block and op-rod are installed.
 
1 - 20 of 59 Posts
Top