Fit and adjustment of the third party floorplate is very important. We fit many Atlasworx aics/CTR footprint mag systems. I have used MDT 8/9/10 shot plastic in 223 & 308 which feed fantastic just a bit short in the load length. Metal 5 shot and 10 shot feed well with me.... others have had small issues. I even run my 22-250 out of the MDT metal 5 & 10 shot as the lips can be adjusted slightly. We have also used the new 3 shot MDT mag which can be difficult to get out as it is so flush fitting. They do work loose and just fall out after a while. Also used AI and Accurate mags that worked without issues except original AI 223 which needs to be re-worked. Magpul seem to need some re-working to get to fit in the narrow T3 action opening.
Highest feeding reliability in my opinion is with the AI, Accurate or MDT metal 5 shot mags.
edi