Force has been using the RIS/RAS with the verticle foregrip since 1998, and we have never seen one RIS/RAS break any part for any reason, period.
I am not doubting your source- just that we have not experienced this.
Nor have we seen any official notifications (as in a PQDR) or the SOCCOM equivelent through channels advising of this.
If your buddy has any official paper on this, we'd certainly like to see it.
Anecdotal stuff is important, and often precedes official notification, but sometimes it is not verifiable or just a war story.
Of course, i'm not sure what he means by locking lugs. This is what is on the bolt, and they will crack/ break when it comes to 10K-14K rounds or so.
There are no locking lugs on the RIS/RAS, but rather 4 MilStd 1913 rails at 12, 3, 6 and 9 o'clock positions.
Is talking about the MilStd 1913 rail ?