Welcome to the forum it is good to have you here. Congratulations on the deer. As for the breech plug, contact Traditions and see it there is a different kind of breech plug that does not use the retainer spring. My black diamond xr also has one, and I never use strong 209 primers in it for that same reason.

As for a better bullet, first thing is accuracy. Perhaps you could in the off season get some of the different brands out there, and do some range time to see which is accurate. Look for something with a good solid construction. Some of the bullets out there are expensive. Others are much more reasonable. Get a pack of Cheap Shots from Thompson Center and see how they shoot for you. I have sure read a lot of good post about how well they bring down deer...

Good luck with your rifle. And again, congratulation on the deer.