I usedd to use 4F and then tried the 3F - I really think it depends on the lock and if the vent is properly placed - at least that's been my experience. If the lock is "tuned" well and you get a good shower of sparks into the pan, it should work fine. I've used 3F in everything from my Fusil de Chasse, which has a large lock to the smaller Siler locks on rifles I've built. If you look at some of the early drill manuals for loading and firing the "firelock" musket, you'll see that in the military, paper wrapped cartridges were carried (I'm talking the era of flintlock muskets). The cock was put on "half cock", the cartridge torn open and a small quantity of the main charge powder placed in the pan and the frizzen closed. The rest of the powder was then loaded and then the ball. This prevented the soldier from having to carry a priming horn. On "civilian" flintlocks, priming horns were often carried and I have several originals in my collection. However, ov er the years, I've had the opportunity to see and study quite a few "hunting pouches" with their horns that were originals from the flintlock era. Some have had priming horns suspended from the strap along with the main horn, some have not. True, a priming horn may have been carried in the bag, but, I still think that some were loaded and charged with the same powder that was carried in the large horn - supposition on my part, but feasible. Don't get discouraged with your flinter - it will take a while for you to get used to what works best for you and your flinter. I guarantee though, that once you get used to it, you will love it! Best of luck to you!