There were some issues with QC fairly recently, after the purchase of some new CNC machines, more a set up issue than anything, but very few made it out.
Now Marlin, after Remington acquired and moved the plant had quite a few issues, with more than 1 problem rifle making it out into the public, Marlin Boards if you want more info.
During WW2 all the weapons plants, would tweak barrels that were not quite straight, I think somewhere I even have a line drawing of a barrel straightener that Mauser used.