I've heard of mag mounted rivets for BB but...

[ar15barrels]

Just use some kind of BB tool with a big flat head, push the shank through the bottom loop and pull the whole magpul up high on the mag like a G-string on a sumo wrestler. Rivet protrudes from the bottom, flat head is held against the floorplate, keeping the tool from bending over.

LOL sorry for the imagery.

The important thing to avoid is the sumo wrestler with the g-string bending over.

[Blue]

Just use some kind of BB tool with a big flat head, push the shank through the bottom loop and pull the whole magpul up high on the mag like a G-string on a sumo wrestler. Rivet protrudes from the bottom, flat head is held against the floorplate, keeping the tool from bending over.

LOL sorry for the imagery.

I'm gonna go scratch my minds eye now

[grywlfbg]

A protrusion on a magpul ranger floorplate would work. It's definitely "stiff" enough.

I think the OP wants to be able to move them from mag to mag. Try these:

http://www.arredondoaccessories.com/category.cfm?CID=1004,2009&PID=fc25l4901itsel&GID=

[Ech0Sierra]

Just back from the emergency eye wash because of vandal's post, I think the ranger floorplates would work fine. I wish I could switch them, but good enough.