Originally Posted by trueblue
Your post mentioned throat erosion. Have you checked your ogive measurement lately?
Throat erosion could be giving you less pressure and therefore less velocity than what you have had in the past.
That is where I would start.
+1. My first thought as well. Wearing out a barrel usually decreases pressure due to less resistance. Additionally, regarding powder, I don't know. I have heard that blackpowder, like pyrodex and pioneer for muzzleloaders loses its "umph" over time. In fact, I've been advised to buy fresh powder annually, but I've never compared shot with the same powder year after year either.
I know that smokeless powder is said to be good for years and years, but I've never heard whether or not it also loses "umph" with time. This would be a good question for the powder manufacturers.