Std Alloy bolt works with a Alloy/Ti Hammer
Delrin bolts require a heavier mass hammer, therefore it should be Stainless/Brass.
Now that I have cast the shadow of doom over proceedings, best be off to either Smartparts (01322 555968) or Planet (0161 872 5572) for the correct answer.
The lighter your bolt, the heavier your hammer has to be to compensate, or so I was lead to believe by Jack @ Planet, but I may have got it wrong, so please check.
silent bob is right you should aim to have a total mass of X amount (cant remember what it is) so if you have a lighter bolt you should have a heavier hammer to increase the mass.
However i dont belive that this will make any real diffrence to the performance of the marker what ever setup you go for, but then i havent tested it in lab conditions with £100,000 worth of computer equipment i've only used mine on the field.