Is anything known to break on these.  I did get 6 mags with it .  1 15 rd and 5 30s.

I had one.   The firing pinhole in the bolt was much larger than the firing pin itself.  The dent to the firing pin made in the primer would actually pop out of the round and all these little brass discs would be all over the inside of the guts of the rifle and sometimes the firing pin itself. The discs inside the bolt would sometimes jam the pin in place despite the spring on the PIN.  So sometimes the gun wouldn't work and sometimes again working full auto just by chambering around.  

Chamber the gun in a safe direction.
That rifle is the top three definitely of my favorite guns.