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Hello everyone,

I think this is my first post in hkpro forums. I have been reading a lot in this forum and i appreciate all the member's knowledgeable input on the various subjects; i have learned a lot from you guys. I have a question on the bolt carrier, the internal rails, and the recoils system of hk 416 vs g36/scar/ar 18/ or similar designs. I know that HK has done a fantastic job in designing the 416, and it has proven itself with extreme tests in different environments. However, i want to know what you guys think as far as advantages / disadvantages of ar 15 / hk 416 action compared to g36 / scar/ ar 18. I know that hk 416 does not have carrier tilt or unnecessary wear on the rails / buffer tube; at least i haven't heard about this issue anywhere. Therefore, mechanically speaking (not ergonomic advantages) which system do you guys prefer and why?

Thanks
Arbi
 

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I hate to say it but the biggest feature of the 416/MR556 is that the manual of arms is nearly identical to the M16/AR15, thusly making it easier for folks who are already familiar with those systems, to transfer over.

The somewhat "self adjusting" gas system is pretty nice, and it has a large number of cross avalible parts with the M16/AR15 platform as well, but isn't that much of an advantage, and other then those things, it really doesn't offer that much of an advantage over other weapons platforms such as the SCAR, etc. so long as those guns are in proper working order.

If I recall correctly, the 416 was initially designed as a product improvement program for the US mil with the express intent to allow an upgrade to the M16/AR15 without having to replace the entire system and help keep costs low while upgrading to a more reliable operating system. That is where its initial strengths were and that is where they remain.

Because of my extensive experience with the M16/AR15 platform, I have chosen to go the MR556 route when I upgraded rather then getting into a whole new platform such as a SCAR or an ACR. The performance of the 416 in trials, torture tests, and in the field with active units coupled with my area of knowledge, on hand spare parts, and competency with a specific weapons platform made the choice for me.

I didn't "want" a 416 style weapon, I looked at all the factors and in the end, those reasons above, coupled with other aspects such as the ability to nitride an MR556 rather then be stuck with chrome (I could have gone ACR with that as they nitride their barrels as well, but then I would have been stuck with their crappy M4-ish profile and a 1/9 rifling twist), and a barrel that I could contour to any profile I wished, made my final decision an easy one.

That is the weapons true strength and the one thing it offers that many of the other platforms cannot. The fact that it's a proven, reliable internal operating system that outwardly mimics a different gun that is widely in use and has a pre-existing supply chain.
 

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I have a question on the bolt carrier, the internal rails, and the recoils system of hk 416 vs g36/scar/ar 18/ or similar designs.
Apples and Oranges. G36 bolt carrier is heavier, the recoil system (spring, guide rod, etc.) is more compact and in line with the piston.

The charging handle of the G36 when used with a rail can be difficult to get a hold of. Other people likewise complain that the position of the charging handle on the AR requires you to move the weapon or your face to pull it back. I fell in love with the G36 from the very first time I shot it. It has a completely different feel from an AR platform, most likely due to the mass of the carrier. With an extended bolt catch to release the bolt from being locked back, the charging handle issue is nearly non-existant.

I've never shot a SCAR, but I don't like the design of the gas block/piston. I'm sure they had a reason for designing it that way, but I'm not a fan. They have to be "tuned" to each gun individually. While FN does this from the factory, any significant change to the weapon that affects gas pressure or duration throws the system out of balance.
 

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Discussion Starter #4
thanks guys for your responses. However, as far as a gas piston design that corresponds to the bolt design and recoil system, which system would you choose if you were a mechanical engineer? Let me put it this way, if hk wants to design another gas piston design, will they choose the same carrier and recoil system on their next project or will they concentrate on the g36 style of operation. I m asking this, because it is interesting for me to see which system is more robust and rigid not because of mass, but because of design. I personally prefer the g36 action or similarly the scar compared to the 416. I think that the internal rails that the g36 action rides provides a more rigid design compared to the 416. What do you guys think?
 

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thanks guys for your responses. However, as far as a gas piston design that corresponds to the bolt design and recoil system, which system would you choose if you were a mechanical engineer? Let me put it this way, if hk wants to design another gas piston design, will they choose the same carrier and recoil system on their next project or will they concentrate on the g36 style of operation. I m asking this, because it is interesting for me to see which system is more robust and rigid not because of mass, but because of design. I personally prefer the g36 action or similarly the scar compared to the 416. I think that the internal rails that the g36 action rides provides a more rigid design compared to the 416. What do you guys think?
What you're talking about is the difference between an internal rail design and a tube design. What made the tube design of the M16 system able to work as well as it did was the fact that it was a DI system. It was not designed to use a short or long stroke gas piston system due to the off-axis stresses of the piston design. Since DI put the piston forces "in line" with the tube, it worked fairly well, albeit very dirty.

To make a piston system work with a tube design, many other factors had to be accounted for and thusfar, in my sometimes not so humble opinion, not a single manufacturer has delt with them completely to date, including HK, although HK has done the best job thusfar.

Every other piston design in history (insofar as I am aware) has been an internal rail design such as the AK, the G-36, the AR180, the FAL, the SKS, every modern machinegun, etc.

Like I said earlier, the 416 was designed as a PiP for the existing M16 family of weapons. Had the M16 family of weapons never existed, neither would the 416. HK would have stuck with the G36 as their flagship 5.56mm rifle deisgn and never given nary a thought to designing a piston system around a tube style design. Quite frankly, nobody in their right mind would do so unless they are simply trying to update an older design.

I'm sure you have paid attention to current developments in firearms design over the last decade and other then the myriad of M16 style clones that come in all sorts of flavors, all major new designs have been A) piston driven, and B) internal rail designs.

The writing is on the wall that to do a piston system correctly and not have it be a mish-mash of compromises, it will be a railed receiver design. Hk knows this and like I said, the 416 was only ever designed as a product improvement, not originally to be a stand alone weapon system. Any future designs will not focus on the M16 platform of weapons, but rather will be along the lines of the G36 or a similar platform.

Lastly, a bit of personal opinion: The G36 design is great....well, it would be if it weren't plastic. Plastic has its places, but in the receiver of a weapon capable of fully automatic fire is not one of them. Heat issues are the biggest concern as have been proven in the past, with wandering zero issues caused by plastic rails, lack of durability at key stress points (folding stock hinge), etc. If they would find a way to make at least the receiver out of forged/milled aircraft aluminum, or find a way to make a skeletonized sheet-steel framework that the plastic is molded over, I would like the system a whole hell of a lot better.
 

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thanks guys for your responses. However, as far as a gas piston design that corresponds to the bolt design and recoil system, which system would you choose if you were a mechanical engineer? Let me put it this way, if hk wants to design another gas piston design, will they choose the same carrier and recoil system on their next project or will they concentrate on the g36 style of operation. I m asking this, because it is interesting for me to see which system is more robust and rigid not because of mass, but because of design. I personally prefer the g36 action or similarly the scar compared to the 416. I think that the internal rails that the g36 action rides provides a more rigid design compared to the 416. What do you guys think?
The XM8 was HK's project to design a better gun, and it had a lot more in common with the G36 then the 416.

That said, the biggest lesson HK learned from the project is that governments do not want a "better gun", what they want is whatever people without a clue put into the request for "another gun". If they understood that from the getgo, we'd be in a different place now. So, to be honest, there is no incentive to build "a better gun".

-W
 

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Discussion Starter #7
I couldn't agree more with all you guys. However, one think that i have been suspecting for a while now is the accuracy of 416. I read somewhere in here that folks get a better grouping with light grain bullets specially with polymer tips. Keep in mind that i do not own any of these guns, but it's logical to think that due to the action of 416 the lighter bullets will generate better grouping compared to lets say match bullets in 70 grain range. The lighter grain bullet will have less back / side reaction and movements in the receiver, which it will result in better followup shots hence better grouping. Therefore, HK had to go with a heavy profile barrel in the 416, not only because of 900 rpm that this action produces, but also to make up for accuracy. Moreover, i think the reason that scars get better accuracy (arguably) is due to internal rail design. I am almost certain that if you unbolt the 416 barrel and slap it on the scar or g36 it will improve it's accuracy with heavier grain bullets. I think that HK had to compromise a lot even though their slogan says no compromise :). Now, like Grumpy and starsnuffer mentioned, the 416 was intended to be an upgrade and improvement to the M4, but it is amazing how far HK engineers worked on ar 15 design to make it as accurate as possible specially for civilian market with their mr556.

Lastly, a bit of personal opinion: The G36 design is great....well, it would be if it weren't plastic. Plastic has its places, but in the receiver of a weapon capable of fully automatic fire is not one of them. Heat issues are the biggest concern as have been proven in the past, with wandering zero issues caused by plastic rails, lack of durability at key stress points (folding stock hinge), etc. If they would find a way to make at least the receiver out of forged/milled aircraft aluminum, or find a way to make a skeletonized sheet-steel framework that the plastic is molded over, I would like the system a whole hell of a lot better.
Hopefully, HK will come up with a design that can have aluminum upper with g36 action similar to what FN did somewhere in the future.

Arbi
 

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I couldn't agree more with all you guys. However, one think that i have been suspecting for a while now is the accuracy of 416. I read somewhere in here that folks get a better grouping with light grain bullets specially with polymer tips. Keep in mind that i do not own any of these guns, but it's logical to think that due to the action of 416 the lighter bullets will generate better grouping compared to lets say match bullets in 70 grain range. The lighter grain bullet will have less back / side reaction and movements in the receiver, which it will result in better followup shots hence better grouping. Therefore, HK had to go with a heavy profile barrel in the 416, not only because of 900 rpm that this action produces, but also to make up for accuracy. Moreover, i think the reason that scars get better accuracy (arguably) is due to internal rail design. I am almost certain that if you unbolt the 416 barrel and slap it on the scar or g36 it will improve it's accuracy with heavier grain bullets. I think that HK had to compromise a lot even though their slogan says no compromise :). Now, like Grumpy and starsnuffer mentioned, the 416 was intended to be an upgrade and improvement to the M4, but it is amazing how far HK engineers worked on ar 15 design to make it as accurate as possible specially for civilian market with their mr556.



Hopefully, HK will come up with a design that can have aluminum upper with g36 action similar to what FN did somewhere in the future.

Arbi
Action type has zero to do with accuracy. The bullet is approx 25 feet out of the barrel by the time the action even starts to cycle.

Accuracy is a function of many things, but not the action of the rifle per se unless you're talking about the difference between bolt action and semi-auto and even then that is debatable.
 

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Discussion Starter #9
well ya but at the time when the piston rod plunges the bolt carrier it will cause some movement in all sorts of directions correct? Meaning the bolt carrier and the bolt face will not go to the same exact position as the previous time and it will effect the accuracy; can this be one of the factors in semi auto system? Back to the subject, i was thinking maybe this is a factor in hk 416 compared to internal rail design of scar for example relating to accuracy.
 

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well ya but at the time when the piston rod plunges the bolt carrier it will cause some movement in all sorts of directions correct? Meaning the bolt carrier and the bolt face will not go to the same exact position as the previous time and it will effect the accuracy; can this be one of the factors in semi auto system? Back to the subject, i was thinking maybe this is a factor in hk 416 compared to internal rail design of scar for example relating to accuracy.
No, the position of the bolt carrier in the receiver has no measurable impact on accuracy and as stated, the cycle doesn't even start until after the bullet has exited the barrel, thusly the forces applied to the carrier by the op-rod have no bearing on accuracy. Your contention that this effects the placement of the bolt itself in relation to the barrel is simply silly. The relation of the bolt to the bore is a function of the bolt dimensions, the dimensions of the round itself, the barrel extension dimensions and headspace dimensions.

Since the real mateup that matters is in relation to headspace which is factored by many things including chamber dimensions, the throat, the boltface, etc. Other influencing factors include the casing consistency, bullet manufacture and consistency between rounds, etc. There are so many factors that effect accuracy to a measurable extent that what you're saying is pretty much not even on the list if at all.

The big argument between semi-auto guns and bolt action guns is the fact that semi auto guns require "looser" manufacturing specifications that allow the firearm to cycle reliably. You put a match chamber in a semi-auto and you get all sorts of reliability issues, especially as the gun gets dirty. Just ask KAC. In bolt guns this isn't a necessity as the bolt is cycled by hand and happens well after the pressure in the barrel has equalized. This leads bolt gunners to claim that their guns can be built to tighter specifications leading to greater consistency, thus greater accuracy.

Those "looser" specifications required for reliable cycling are found in ALL semi-auto combat rifles, therefore it makes no difference if you swapped a 416 barrel to a SCAR or other railed platform because they have the same looser specifications to allow reliable function.
 
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