Good info utf +1
GOF, for your new gun test (to determine if it should go back to STI to be made right) there is no better, IMHO, than the ubiquitous WWB. Best new gun test ammo I have found! It's a gud 'ole
It's reliable and clean compared to most range ammo and the brass is of good quality for reload or trade.
If you don't have an established new gun check-out procedure I'd like to suggest the - Break-in is a criminal activity or Noob mis-speak.
Works well for this old codger.
For PD ammo I'd look at this Buffalo Bore offering to see if it runs well in your new purchase. (after you're sure there are no issues with the new STI)
.45 ACP +P BUFFALO-BARNES Low Flash Pistol and Handgun Ammo
Another round I run in my Colt Defender is;
.45 Auto+P 230 gr HP XTP TAP FPD
If you don't want +P ammo this Hornaday works well;
.45 Auto 185 gr FTX Critical Defense