It is my understanding that a standard USGI mag body holds 11 rounds of 458 scocom.
I also have seen that some places offer USGI-ish looking mags that are allegedly 10 round 458 socom mags.
If they are advertised as 10rd but really hold 11 this could be a serious problem for people behind enemy lines.
Is there a magazine plug or a follower with extended legs to ensure that 458 socom when using a standard USGI body will truly be a 10rd mag and not an 11?
“Permanent” is a legal construct that varies by statute. In some statutes, something is permanent if it requires disassembly to reverse. I.e. if you have to remove a floor plate, it is permanent. Ohio was a good example. But, you will have to check your local laws for the definition you must meet.
Anybody with a backhoe understands that NOTHING is really permanent!