I have no doubt they are not tested.
Looking at the design of the mag the feeding ramp is actually a part of the mag itself. I'm sure it would not take much to resolve. The plastic is mildly textured and I reckon some fine paper would sort it out.
I have put the rifle away so I'm unable to say how many calibres suit this particular magazine but I recall its several.
Im using SN Woodleighs and I reckon something a little pointier would feed OK as the rifle is. Despite this small issue the rifle is more than I expected