i use 3/4 in my tc hawken....same lock i think....but i find some are a HAIR to long....i have to take my lock or gun with me when buying flints....i even fit a lyman frizzen to the lock....and its still the same thing.....i think my hammer is bent just a hair or something....i heard of people messing with the hammers to get a better spark....heating and bending them a certain way......so the flint will take more metal off id guess....and i guess it works....it makes sparks.....i called TC to see if theyd update mine and they said replace the frizzen and touchhole myself......i had the old touchhole with a screwdriver slot and just a hole....i got the new ones with a cone and a allen key hole...and a lyman frizzen.....cant complain...goes off like a champ...