This pack should give the Hunter Pistol, Hunter Blunderbuss and Gatling Gun a natural-looking melee swing with a 0.1-second upswing. If your guns still swing slowly or awkwardly, work through these checks.
Check the requirements
1. Better Combat must be installed. The pack works by adding Better Combat compatibility. Without Better Combat, the custom swing animations and faster upswing will not apply.
2. Soulslike Weaponry must be installed. The pack only targets that mod's guns. Other mods' firearms are not changed.
3. Use the right weapons. Only the Hunter Pistol, Hunter Blunderbuss and Gatling Gun are covered by the pack.
Check the data pack itself
1. Data packs belong to individual worlds. If the swings work in one world but not another, the pack is probably missing from the second world's datapacks folder.
2. Run /datapack list and confirm the pack shows as enabled. If it appears as available but not enabled, use /datapack enable with its listed name.
3. Run /reload after making changes, or leave and rejoin the world.
4. On a multiplayer server, the pack must be in the server's world. Ask the server operator to check it there, since a copy in your own singleplayer world won't affect the server.
Retest
Hold one of the three guns and hit a mob up close. You should see a quick upswing of about 2 ticks before the hit lands.