On Saturday June 13 I took my Mini6.8 (stainless/synthetic) out for a little bit of shooting. I had purchased a couple black/polished-steel 10-round Ruger factory Mini-30 mags from another guy over at CalGuns.net. Visual inspection on the M30 mags compared to the M68 mags the size, followers, thickness all seemed pretty dead-nuts the same. A test fit also went well - the M30 mags clipped into the M68 magwell just fine. The M30 mags are not dropping out as freely as the 5-round M68 mags though - but that does not concern me they do pull out easily enough and the magazine release is right there at the back of the mag so pull release with my thumb and pull the M30 mag out, no problemo.
My first firing test of the M30 mag I placed 4 cartridges into it. Flawless - not a single issue. Second test was 7-rounds. Again flawless. Third and fourth test were both a full 10-rounds and both had same issue. First three rounds would fire and eject but the next round would fail to load fully. I had to push the slide handle in order to fully load the round into the chamber.
One other item, I installed a washer/buffer behind the recoil spring as is commonly done. I don't think that would affect only rounds 1-3 of 10 but I mention it just to be clear. And I was shooting Hornady 110Gr VMax rounds.
Conclusion: I am pretty happy using the M30 mags in my M68. A little more testing to see if I continue to have issues.