Didn't the Hawken's make lighter weight rifles too? And didn't all gunsmiths in the 1790s-1850s vary what they did on almost every rifle they made? I know the Appalachian long rifle makers did, even the trigger guards were different on several Gross rifles that I have seen and have. I'm not going to go look at the weights of all known Hawkens, but I'd say the basic features are Hawken:
Half stocked, with a nose cap
Two barrel keys with escutcheons
Heavy caliber, relatively heavy barrel
Percussion lock
Triggers Double-set
Buckhorn open sights
Patent breech or hooked barrel
Iron furniture, including the mountings
What are you postulating is "not like a Hawken" that is not minutiae, or sample varience between individual Hawkens? The weight?