I know that this is an old thread but I thought I'd see if anyone else has a Springfield Stalker.  I recently got one in .45 caliber.  It looks like a well build rifle.  The ramrod thimble and ramrod are missing on mine.  I do, however, have one of those old telescoping H&R ramrods.  That has to be the worst ramrod ever made.  I wonder who came up with that idea?  I'm thinking about doing a little customizing on mine.  Thinking of fitting it nose cap, ramrod entry pipe, under-rib and a couple of thimbles.  I have an old Navy Arms Buffalo Hunter in .58 caliber.  It has those features. 
There is not a heck of a lot of info out on these rifles.  
If anyone has a .45 Stalker I would like to find out what loads & bullet/ball size you are using.