We've had a few Colt LE6520s come through the shop in the last year with receiver ramps cut post anodizing. I really haven't examined many RRAs up here, so I can't comment on what they do.
Good job with the chart referencing who does what. Flow of info is always good.
For my personal use, on semi-auto guns, I'll admit I'm not particularly concerned with the type of feed ramp on the gun, as long as it is correct (ie: no M4 receiver with rifle barrel extension). The newer CF C8 carbines apparently run with M4 type barrel extensions in A4 type uppers, I've not
heard of feed issues. Some of our rifles (Stag/CMT mainly, disclaimer, which we sell) have M4 extensions/M4 uppers, most have rifle ramps/A4 uppers.
I see reference to hollowpoint ammo issues, I don't have personal experience with problems feeding HP that I could trace to extended ramps preventing (ie, misfeeds impacting the front of the mag, rather than the receiver below the barrel extension), but I sincerely take peoples word on it, particularly so with longer heavy bullets. However, 97% of what I shoot is 62gn ball ammo, with a bit of 68gn BTHP.
I understand the reasons issued for the use of M4 ramps, particularly with full auto, and certainly don't object to them or anything (!), just not something I've had cause to think about. I request M4 ramps/uppers on full auto carbines and custom orders.
On the Colts I referenced above, properly done, the bevel in the receiver is not much aluminum to displace, I reckon they're working fine.
All the best.
Walt
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