[jag609]

Guys, I want to make sure im understanding the manufacturer's site on the http://www.armsmounts.com/catalog.php?action=124&item_id=46 " Available in both Civilian(C) and Military(M) configurations. (Installation of Military S.I.R. ® Variants requires removal of the Delta Ring/Handguard Retaining Ring)."

does this mean that the civilian model fits OVER the existing handguard?

and since it's advertised as allowing for 'co-witness for head's up display', how does the front being lowered actually help with that...

thanks guys

[illspirit]

No, it doesn't fit over the default handgaurd. Those still have to be removed. The civilian version is just cut out by the receiver so you can leave the delta ring on, just in case you want to switch back.

As for co-witnessing, I think the lowered bit helps provide an absolute co-witness, whereas a full-height rail would generally provide a lower-third co-witness with most optics. Or, something like that.