I'd say you need to revisit your "bench" technique first. Techniques used with modern rifles quite often don't play nice with our guns.
Longrifles can be quite sensitive to how they're benched and held. Try this- hold the rifle as you would offhand. Transfer to the bench using the same hold points. Rest ONLY the back of your forward hand on the rest. Grip the rifle barrel with your forward hand as you would offhand. Do not "crush" grip the wrist of the stick and be sure that your trigger hand placement is consistent. What you're after is to replicate the same recoil dynamic as offhand but with the aid of a bench to steady the aim a bit. Rifle barrels move under recoil in a harmonic wave. Where you put that front hand and how you grip the rifle will absolutely change how your gun groups. Where you rest that long rifle barrel on a rest will dramatically change how a longrifle will group.
Following is a proof picture. Rifle was brand new Kibler kit custom built by one of our forum members. He was having issues getting it to group. The picture is my first 4 shots from the gun using the exact same load but with the technique I just described. Pathfinder was getting inconsistent and sometimes large groups. He has since changed to my method and his groups are now similar to this one.
Kibler Colonial 54cal flintlock at 50yd. Diameter of the ball is incorrect.
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