That vent is perfect. Be patient, don't overprime it. Most guys think they need a bucket full of 4f to make sure it works. That slows it down and burns your eyebrows off, ha ha. Hence the nickname flinchlock. I've hunted with flinters since the early 1980's, love them. You need a strong mainspring, hard frizzen, and good flint. Lots of sparks and you are in business. Practice, practice, practice to get used to the lock time. Enjoy it, most guys won't have what it takes to hunt with one so consider yourself a rare commodity if you do. Ha!