Hi,
Please read what I write carefully. Before inserting any new pins, pass appropriately sized drills through the holes with the barrel in place to make sure everything lines up and the holes are clean. I would twiddle and push the drill bits in using my fingers rather than using a drill to be gentle and avoid enlarging the holes. Finishing nails are fine for the pins holding the ramrod thimbles. You will need 5 of them, 2 for the long front thimble, and one each for the others. Using calipers, measure how long each pin needs to be and cut the nails accordingly. Then turn them in a drill held in a vise so you can slightly round both ends with a file. The rounded ends will prevent the pin from catching and splintering the stock as you tap them in. You will need slightly larger and more durable pins for the barrel because they may be removed and installed periodically unlike the thimble pins. I suggest 3/32" piano wire or spring steel. Check the holes in the barrel lugs and if they are smaller than 3/32", try 5/64" pins. Measure the pin length as before but cut them just a tad shorter than needed and round both ends. Tap them in so one side is flush with the wood but the other is inset. On British muskets all pins are inserted and removed from the side plate side of the stock. The hole around the inset end of the pin will guide your punch when removing the barrel pin preventing it from slipping off the pin and damaging the stock. On real Brown Bess muskets, the forward swivel screw goes through a lug on the barrel. Unfortunately, Pedersoli neglects that detail and relies solely on the overly thick stock for support.
If you want to bring your Bess up to a higher historical standard, here is some instruction:
https://www.muzzleloadingforum.com/threads/new-reworking-a-pedersoli-brown-bess.107405/
dave