Since there seem to be somewhat mixed comments about A-MERC brass here (for example, I think that it's crap and some others think that it's OK), the best thing to do is to test the brass yourself if you don't want to believe the negative comments and give it up...
Most of my A-MERC experience has been with .45ACP and 9x19mmP brass. The problem has been mostly related to the brass being considerably too soft.
Try this experiment. Take several fired A-MERC cases and several cases from other manufacturers and run them through your carbide sizing die (I generally use Lee carbide dies for handgun cases). The carbide sizing ring should swage the case back to spec without displacing any brass ahead of the sizing ring. Cases of the appropriate hardness will simply look smooth and 'new' after sizing. If you try this with an A-MERC case, the sizing ring will push up a ridge of brass, and you'll be able to see (and feel) this ridge near the base of the case quite clearly...
Such cases should be discarded.
I've found that about 95 percent of the A-MERC .45ACP and 9x19mmP cases that I've resized have been too soft. Ocassionally, I've found ones that looked just fine after sizing, but it's literally not worth my time to walk through all the lemons for the single pearl.
The only other 9x19mmP cases that I've found also to be too soft are some of the Chinese ones. However, the ratio of too soft to OK for Chinese is much lower, and I generally run these through my sizer and just discard the 'ridged' ones...
Test your brass and see for yourself...
If it tests out OK, use it...
For me, that means discarding the A-MERC brass into the scrap bucket.
YMMV...
Forrest