I've got two TL3 Dashers in MPA's.
My go to mag is a AICS 10 rd with a Primal Rights kit. The mag lips are tweaked out on the forward edge. The spacer is glued in, and I've got a +2 Seekins base plate. I also removed the binder plate for extra OAL running Sierra 110's with a longer throat. This mag works pretty much flawlessly for me, as well as any mag as ever worked for any round.
My "other" mag is an ARC. It's about a 98% mag for me IF I keep it clean. When it gets too dusty, the side pressure from the sharper stack angle plus the friction from the dust can cause the rounds to bind up on me. It's nice because it's short, and because it works well with pressure on the mag, which the AICS doesn't handle quite as well. Also, since it isn't modified I can use it for my 6.5x47L as well. Nice to not paint ALL your mags into a Dasher corner.
As soon as I get two kits from Josh in, I'll have a couple more AICS 10 rounders in action.