Friends don't let friends shoot mixed brass. Ain't this the truth. We only use LAKE CITY brass for our 300 AAC Blackout brass. Why? Because friends don't let friends shoot mixed headstamps But seriously, each brass manufacturer's brass is slightly different in thickness, when you are converting a piece of brass like we do to make Blackout, that hair of thickness, is a WORLD of difference. We have tested every kind of military & commercial brass out there. Lake City beat them all for performance and durability. Why not make mixed headstamp brass? It's cheaper right?! You get what you pay for. Since each brand of brass is a different thickness, the trim length and shoulder setback will vary, giving you very inconsistent results at the range, or the hunt. Not worth missing the shot. Invest in Lake City brass, it's a one and done type of deal if you find it to pick it up and reload over, and over, and over (16 times over is what we are at so far)!!