Not bad but try with different amounts of powder and see. There is an ideal spin rate RPM for every gun / projectile and it takes experimenting to fund it. That is what makes BP so much fun. You adjust spin be changing velocity. The amount of powder charge determines that. The "sweet spot" charge is different for every gun. Even 2 identical guns from the same manufacturer shooting the same projectile will have different "best charge".
Of course the caffeine charge can also come into play. It does with me.