Steel Plate on Canadian 180 Designs echoed on MCX Spear

[Ustauk]

Some people have complained that some 180 based uppers have steel plates on the side, like the MCR, Lynx and Crusader Sentinel. The plates were kept larger to simplify manufacturing, but the wisdom of the steel inserts have been echoed in the design of new American Forces rifle, the SIG Spear, albeit in a smaller footprint. Ian at Forgotten Weapons posted a video on the firearm, https://www.canadiangunnutz.com/forum/showthread.php/2280432-Forgotten-Weapons-SIG-Spear-Videos?p=18913900&viewfull=1#post18913900, and noted the following:

It's also worth pointing out that we have this steel insert screwed into the receiver.
This is basically the cam lug track on the inside of the receiver.
This is an area that potentially would get rather worn with a steel camming lug in the bolt carrier rubbing against an aluminium receiver.
So that has been made a steel insert so that if there is excessive wear it can be replaced. And it can also be hardened such that it won't need replacement quite so much.

 

[greentips]

Colt was the first to put steel insert into cam pin recess back in the days of the first push rod gun commercially available, aka Colt 6940P and then it got carried over to LE901.

But the idea was developed in 1968 by Winchester, all the way back to vietnam war, when they tried to convert M16 from DI to push rod.

SIG MCX and later SPEAR are basically an AR18 stuffed into an AR15 dimensioned upper and using truncated AR BGC. When it goes with a tubular BGC with a rotating cam pin on top, it has same issue as a typical AR system like 6940 P and HK416 when it comes to cam pin track wear in the upper. That wear doesn't do anything, but hey......the receiver doesn't "hold" the cam pin in place. it bothers people.

Don't know about these 180 style rifles, but the 180 doesn't have any recess in the receiver for the cam pin, the steel plate is there for difference reasons

 

[Ustauk]

Spectre LTD's Spectre Steve on Instagram said about the plate on the left side of the Crusader:

...that’s a steel plate that the cam runs on. It’s one of the key features that makes this gun super reliable and long lasting.

Not sure about the others, will defer to what is reported.