Clean the barrel

I've been casting and reloading for over 5 years now and still sometimes the little things get everyone. I went out to the range last Friday to test out a proven load in a 300 blackout pistol. Well my rounds weren't seating all the way and a few even got stuck and dumped powder. I finally took time today to sit down and look at what the problem was. Boolits we're all sized to .310", the casings we're trimmed to the correct length, they were sized correctly,, couldn't find the problem. I determined that even though they were 130grn I must have seated them too long. Just before I went through the task of seating then all deeper again I ran a few patches through the barrel to clean her out. Wouldn't you know a small price of lead build up was the whole problem. All rounds chamber just fine after that. We will see how she does on the next range session, might need to have the throat lapped. Just remember to keep it simple stupid.