Question on the HK MR556

[July Johnson]

I'm gonna buy one after the SCAR 17 comes in but some guys are saying I should buy a "416" bolt carrier. I looked around and there expensive (600-800ish). Do I need one???? they say it stops "bolt bounce"????? Anyplace cheaper if I need one???? The gun costs a lot but I have been reading that it is a good gun so I do not mind spending the money if it helps.

[Ed L.]

The MR556 has a protrusion that will prevent a 416 bolt carrier from fully closing. The MR556 has a bolt carrier with an indentation that allows it to fit. This has to do with German laws and war weapons not being available for sale to civilians or for export without whatever government approval. Thus certain features are different and certain parts are not interchangeable. Below is a schematic of the MR556 bolt and a photo of the MR762 bolt with an arrow pointing to the indentation:

[m4hk33]

the mr556 is fine as is.

[montrala]

You need 416 carrier only if you want to put your upper on full-auto lower. In this case you also need to modify barrel extension by milling down protrusion mentioned by Ed L. There is no other reason for or benefit from using 416 bolt carrier.

[Leaveammoforme]

I'm gonna buy one after the SCAR 17 comes in but some guys are saying I should buy a "416" bolt carrier. I looked around and there expensive (600-800ish). Do I need one???? they say it stops "bolt bounce"????? Anyplace cheaper if I need one???? The gun costs a lot but I have been reading that it is a good gun so I do not mind spending the money if it helps.

Just a heads up... I will buy the factory take down and pivot pins from you if you replace them with standard pins.

[HKGuns]

the mr556 is fine as is.

This...........

[Ed L.]

Just a heads up... I will buy the factory take down and pivot pins from you if you replace them with standard pins.

Can you explain your preference for the HK Pins that need the special tool pop the pins out and even to put them back?

I have a new MR762 and I am planning on having the pivot pin and takedown pin replaced with standard pins so I don't have to use the stupid tool to be able to pop open the upper as well as close it.

When I first took the gun apart and then tried to reassemble it, the pin would not go back in. I finally figured out that you have to use the takedown tool and push into the takedown pin through the hole in the receiver and then simultaneous push the takedown pin in the opposite direction to get it to close back.

[Leaveammoforme]

The HK pins tighten up sloppy upper/lower fit and I like that they lock in. I put a set in my most recent build that was geared towards being able to be thrown.

[Ed L.]

Thanks.

I can see that this new MR762 is going to more of a pain than I thought.

[HKGuns]

Thanks.

I can see that this new MR762 is going to more of a pain than I thought.

I don't think so, I think you will find it a joy to shoot and cleanup minimal.

I don't mind the pins as they do lock it up tight. You will get used to them if you leave them in place.