Check out the 6945 (gun on the top) in this pic. It has a fastener in the left side of the upper receiver.
On the inside is a small steel insert that acts as a bearing surface to prevent cam pin galling in the upper. Never seen anything like that before…
crap, now i have to throw all mine away to get that plate!!! cool feature, thanks for sharing. can’t really see what’s going on in the second pic though 
I vaguely recall seeing a thread about that here not too long ago. I believe that insert is for a piston upper (6940P?). Did you or someone else build that upper? Isn’t a 6945 monolithic?
This is Pappabear’s COLT Factory built 10.3 monolithic upper. It’s like the SBR version of the 6940.
(t15, look into the ejection port on the second pic to see the steel piece… it’s centered in the middle of the port)
I saw those when the 6940 started shipped a few years ago. It makes sense.
Oh yeah, I see that now. Small pics on the phone…
So the 6940s have them too? I thought maybe it was unique to the SBR. Interesting.
Yup, all of the 6940 series monolithic rifles have them.
Interesting. Pappabear had one a few years back. Either I didn’t notice it, or the older ones didn’t have it. ???
https://www.m4carbine.net/archive/index.php/t-107431.html
This is the archived thread in question if anybody was looking for it.
That one even has one of LWRCi’s employee/shills chiming in. :sarcastic:
I love how they used to just inject some shit about LWRCi when no one asked. Haven’t seen those scum bags on the forum in a while.
The first 6940s didn’t have the steel cam pin plates but the plate was added to all 6940 uppers once colt came out with the 6940P.
The plate is really only needed for the piston gun.
Haha, yep! It definitely has been a long long time since I have seen those guys around. I thought that I saw a more recent thread regarding this but I couldn’t find it unfortunately. =/
Very interesting, I’ve always felt and heard external piston designs have more wear and tear on the parts.
More recent thread about that fastener and plate.
https://www.m4carbine.net/showthread.php?165100-What-s-this&p=2077552&highlight=#post2077552
That’s the one I was looking for earlier!
That makes sense. They likely just run them on all the uppers rather than have two different part numbers.
We have LE6943CK and LE6945’s here with that plate. So it is standard.
C4
Nope, mine doesn’t.
Must be an early rifle. Does it have the “patent pending” stamping on the left side?