Re: H-870 powder is there any left
When cleaning your 338-378 try running a patch saturated with some kind of light oil, such as 3 in 1 or other light oil through the barrel after extensive cleaning and before your first shot. This procces works best if you have a very clean metal surface in the bore. What this does is lubricates the first (foul) shot and reduces the overall fouling in the long run. In MOST cases one can expect to double their shots between cleanings before accuracy goes AWOL.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.