A large barrel does not necessarily dictate a large lock. For example I used a the large L&R that TOW calls an Ashmore on a 1" barreled rifle years back and the lock was actually way to big even for a Hawken type rifle.
I used to own the rifle below, it is certainly not out of proportion.
Small Siler and the barrel is a swamp either 1 1/8 or 1 1/16" at the breech. Think its the larger size.
This does not make it 100% HC, but the lines are not compromised by using the smaller lock.
Dan