It also jammed constantly, so I sold it for considerably less than my payment.
As it turns out, it was due to the magazines I was using. I had 5 identical USA 20 round magazines. I never tried the gun with any other types (much to my regret). I went on a usenet forum (rec.guns I believe) and brought up my delimma with the gun's propensity for jamming. Everybody responded by asking if I had been using USA magazines in the rifle. Turns out that those magazines had to be slightly modified to work properly.
I wish I had known that when I had the gun. I'd still have it.
I was warned early on about the undesirability of using after purchase mags, so I buy only original mags. I think that it is best that way as well.
Don't ever use USA mags in anything. They're crap.
Reliable high-cap mags for Minis are hard to find and (very) expensive.
It's easy to get reliable 30-round AR-15 mags for $15 - but you can't get reliable high-cap ones for Minis under $50, usually a lot more. The only reliable high-caps for Minis are the Thermold 30-round and the factory Ruger; count on $70+ for factory Ruger.
Add to that general unreliability. The Mini that I eventually got rid of just sometimes failed to completely close its bolt - even though it appeared to have.