I just purchased a grey hawk from a forum member in .50 cal, would have been interested in the .54 though lol. What condition is your grey hawk? The only thing i have now that fall within the price of a grey hawk is a lyman .36 cal navy (these are rare with fast twist barrels and chamber diameters at or over bore diameter for better accuracy), if no colts wanted i might even be able t trade a 1858 euroarms that doesnt look to be shot..but also depends on the condition of rifle etc. If you are willing to pay and do a partial trade i can offer a highly slicked up 1851 navy....comes with cap post to prevent cap jams, action/hammer sheild that prevents cap fragments and fouling from getting inside the gun, two part torsion wire spring set up for trigger and bolt to replace the stock stamped steel trigger/bolt spring, action stop to prevent over travel when fully cocked, cam and bolt leg adjustment, a "forever" hand which is basically replacing the flat steel spring off the hand and adding a round wire spring that if it ever breaks can easily be replaced instead of having to replace and resize a new hand, and after market stainless steel Uncle Mikes nipples..its really slick and set up for competition. Only has 12 rounds through it...2 per chamber just to test it out. If you want feedback on the work i do on the guns you can search the high road forum or i can send you links. Thanks!