I wrote to this about a week ago here:

http://www.huntingnet.com/forum/tm.aspx?m=2533545

I cut and paste it into here for your convenience, best wishes on bullet selection, it is >>the<< most important part of ML shooting, 'cause it is doing the work of the gun.

Bullet selection for the .45 cal is sparce, they make a Barnes MZ for the .45:

http://www.midsouthshooterssupply.com/item.asp?sku=0003540052

that is one of the best, if it will shoot well in your gun. Hornady XTPs would stay together better than a PB, but they separate from their jackets at hight speed (i.e. close shots):

http://www.midsouthshooterssupply.com/item.asp?sku=00072XTP24520

If ya wanted to get a bit more range than the Hornady XTP, then there is a .45 Hornady SST:
http://www.midsouthshooterssupply.com/item.asp?sku=0000367132


A better bullet would be the Speer Gold Dot at .400 diameter, 180g (there are 100 in a box of these bullets for $22, that is 22 cents each, you can beat that):

http://www.midsouthshooterssupply.com/item.asp?sku=000214406

you of course would mate this with a Sabot designed for .45 cal bullets such as Harvester Crushed rib:
http://www.midsouthshooterssupply.com/item.asp?sku=00072H14540BR

or Harvester Black:
http://www.midsouthshooterssupply.com/item.asp?sku=00072H4540B

Those are your choices and all are better than a PB in my opinion, but that is mine only, not a universal truth. Best Wishes on your bullet selection.
Chap Gleason