You're welcome. But NOLA_Ken deserves credit also, because there is apparently no difference between the endcap of the Model-1842 Springfield and the Model-1847 US Artillery Musketoon he linked to.
Far more Model-1842 Springfield muskets were manufactured than 1847 Artillery Musketoons. So, your endcap is statistically much more likely to be from a Model-1842 musket, but the 1847 Musketoon is still a possibiity. No way to know for certain, because both were .69-caliber gunbarrels.