GMB IBO #910100 - #9100105 - #910110 all claim to fit the .50 caliber Thompson Center Hawkins (and under) and also the Lyman Deerstalker, Deer Stalker Carbine, and the Lyman Trade Rifle according to the charts.
So to test that theory out, since I have two .50 caliber T/C Hawkins Flintlocks, and a .54 caliber Lyman Trade Rifle Flintlock, I took the barrels out to see if they were interchangable.
THEY ARE NOT! The .54 caliber Lyman Barrel would have split both of my T/C stocks if I had tried to force it, and the tang knob on the T/C does not fit the Lyman tang slot. There would have to be some adjustment there. So while GMB shows the same barrel for both rifles, the factory barrels are not interchangable. Hope this really confused the devil out of you!!! Just kidding.


I would have tried one of my GMB's in the Lyman, but they are all percussion and so the bolster gets in the way of the lock... sorry I could not help you more.