question about gas piston AR uppers

[Pablo]

The first pic is a HK 416.
It shows some unusual wear in the upper receiver. Specifically, wear caused by the cam pin on the left side of the upper receiver but below the charging handle. The wear pattern looks like a channel about 3/8ths of an inch in length and tappers towards the rear of the receiver. This is a new rifle with 700 green tip military rounds down the bore. I've never attached a can to this rifle. Approx. half of the round count was on select fire.

The second photo is a conventional DI US Gov Colt M4 with an estimated 4500 green tip round count. The wear is in the same location but considerably less.

I've examined two other HK 416s that had exactly the same wear indication. These three HKs that I've examined are considered reliable and dependable rifles.


So I have a few questions for anyone more knowledgeable than me.

How many rounds before the HK upper receiver needs to be replaced?
Anyone else seen this same wear in their HK 416s?

Does any other brand of piston upper show the same or similar wear pattern? OR, which brand piston upper does not develop this excessive wear on the upper receiver from the cam pin?

[markm]

This is no different than a real AR. All of my ARs have this to some extent. The wear is somewhat self limiting, and completely negligible.

[Tspeis]

Another gentleman asked this same question recently. HK says it's normal and purely cosmetic. It will in no way decrease the strength or life of your receiver. My upper had just over 2,000 rounds through it and showed similar wear patterns. It never gave me any problems.

There are HK416's that have gone over 30,000 rounds during testing with no parts breakages so I assume the receiver should be fine through high round counts.


Tspeis

[VA_Dinger]

Every AR I own has the same wear so it cannot be an issue.

[Seth Harness]

I have a converted piston rifle and mine has the same wear. Dont think its that big of a deal.

[Tspeis]

Pablo,

What are the date codes on the three HK's you examined?

Just an FYI, this was an issue with some of the earlier guns HK put out partly due to the fact that they sourced cam pins from US suppliers. They currently make their own cam pins for the system and have made mods to the receiver so it's much less of an issue on the newer guns. The 417's will likely not have this problem.


Tspeis