John, I’m not an expert in this; however, I once had a Marlin 93 where the forend (close to 100 years old) had shrunk, became loose, and developed nearly a 1/8 inch gap between the wood and the receiver. I sold the gun without repairing it. But thinking about the repair I thought Acraglass in the right place, and if the Acraglass showed externally and didn’t look right send it to Mark Larson to work his magic with grain matching. I hope others come along with more suggestions.