Gary - that's a super job!
I have poured a number of nose caps on half and full stocks that I built from scratch in years past. Years ago, I bought one of the pewter bars that T OW had but have never used it. My examination of many originals - both half and full stocks, made me come to the conclusion that many were poured using lead. I used either a harder lead or foundry type as I had a 5 gallon bucket of it given to me years ago. The first one I poured was really stressful, because as you know well, by the tim e you're ready to pour you have already put a lot of work into the stock blank. It turned out well though and each one after was an exercise in improving the form for the pour, etc.
IMHO, making a horn nose cap is much harder in regards to fitting, forming and getting it to look "like it grew there". Your craftsmanship is something to be very proud of as it looks great! I hope you'll post more photos of your build and describe the components you are using - sounds like a great squirrel rifle! Thanks for sharing!
Jim