Congrats on the G37. My current favorite GAP is the G38. Great gun, great round.
Good news is that you can share lots of components (and equipment).
1) Dies - Use the same for ACP and GAP. Note that the Lee ACP dies are at their limit for GAP. Lee has shorter die bodies and less threads than other dies. I ended up getting a second set of ACP dies to leave in the dedicated GAP toolhead.
2) Powders - Use Bullseye, 231, PowerPistol, Unique, AA#2 and WST. All work great in GAP and ACP. You'll find that the GAP usually requires about 1gr less per loading compared to the equivalent ACP load (WST seems to be the exception).
3) Shellholders/plates - Even with the GAP's rebated rim, the same shell holder/plate works well for both rounds.
4) Projectiles - I like the Rainier 200gr plated hollow points. Midway generally has them on sale. This projectile works well in my G38, 1911 and P90. Rainier also has a 185gr what works well in both. I haven't bothered with a 230gr projectile yet.
5) Primers - Yep! If you convert your ACP brass to small primer, you can interchange primers between GAP and ACP. All my active ACP brass is now Speer or Federal small primer brass. Love it.
6) Ammo cases - You can use the ACP MTM cases to store GAP rounds.
Hope that helps
Last edited by dudel; 03-15-2011 at 18:31..