AR10 dustcover: what happened here?

[dvdcrr]

OK, I have not been able in my mind to really figure this one out, maybe you can help me.
A coiple years ago I bought a new SW M&P10 rifle. After shootin a few rounds I noticed the dust cover pin had walked forward and the dust cover nearly fallen off.
After looking at some pics and my rifle, it appeared that the pin was too short. But when I contacted S&W they stated that there was only one part # and one length of pin, same as an ar15.
SO I bought a captive pin/Strike Ind. cover and forgot about it. But from time to time I wonder if they were right, then my rifle must be missing something at the rear of the handguard which would have butted up against the front of the pin. I just don't think this is the case. What say ye?

 

[Mobuck]

I assembled an AR 15 upper last night and noted that the dust cover pin would just barely stay in place. I don't know why they don't just put another of those little e-clips on the rear of the pin rather than depend on the barrel nut to retain the pin.
I just measured an AR 15 DC pin @ 3 7/8" and the AR 10 DC pin is at least 4"(can't see the rear as that's a blind hole on my PSA AR 10 upper).

 

[Nathan]

The better question is why did the maker of your barrel nut not continue this same functionality or offer an “upgrade?”

 

[dvdcrr]

Thanks for the info! I think maybe they do require the longer pin.

 

[Mobuck]

"The better question is why did the maker of your barrel nut not continue this same functionality or offer an “upgrade?”

"mil-spec" should be sufficient

 

[Sharkbite]

The better question is why did the maker of your barrel nut not continue this same functionality or offer an “upgrade?”

"mil-spec" should be sufficient

There is no such thing as a “mil-spec” AR-10

 

[Mobuck]

"There is no such thing as a “mil-spec” AR-10"

The "mil-spec" I was referring to was the AR 15, but you are correct. I dislike the term "mil-spec" but so many use it that it's the only acceptable reference.