Different rifle entirely. Firehawks have a fixed plug, Black Diamonds are removable. Firehawks have a 1-38 twist, Diamonds are 1-28. All Black Diamonds have q.l.a. muzzles. Some later production Firehawks do.
I thought my Black Diamonds were the be all to end all in striker fired muzzleloaders. Until I got a Firehawk... I had 2 XRs a. Super.45 and a .50. Excellent rifles. Ditch the 209 module ( its filthy and unnecessary) and the " flame thrower" nipples, also dirty. I use single port Tresco nipples, both musket and #11. Cleaner, and I also got 100 fps higher velocities. Chrono'd with the same load no other changes.Not difficult to clean at all.
You CAN'T go wrong with a walnut stocked, stainless Black Diamond XR! I once paid more than $150 just for a walnut stock!