There is a risk of slam fire, however the biggest cause of that that I have read about is not inserting the primers deep enough and using brands of primers that are known to be quite soft.
I've got over 500 rounds of reloads thru my M14s using CCI, Federal, Winchester, all went bang and have never had a slam fire.
But I do try to get them seated 5000ths at least. Also have never had any punctures either with "soft" made primers.
Have had plenty of complete punctures on some Chinese .308 surplus and then a bunch that were seated so deep all I could get was a pin strike with no bang.