Howdy- if the nipple is too large, you may have a musket cap nipple installed on your breech plug, instead of a percussion cap nipple. If you do not have a screw-on separate nipple on the breech plug, you have a 209 conversion breech plug on your T-Bolt which will only use 209 shotgun primers. I own 3 T-Bolts and before they were discontinued, many came from the factory with the 209 conversion kit installed already. Many of these were sold through Bass Pro Shops. I hope this information helps you out. Let me know how you make out.