I just took my SDB priming system apart and adjusted EVERYTHING. There are several adjustments but I do not claim to know which one may be causing that issue. Here is where I would start if you desire to jump into it. It is not difficult at all.
1. Remove the priming assembly which consists of three bolts. Note the hole the cap screws came out of as some are longer than others.
2. Remove the primer slide assembly, it comes out by taking the spring off (it won't fly off) and by turning the assembly sideways and removing it. Now you should have the assembly in your hands.
3. Now, here is where you need to get your manual out. Measure the cup height from the base of slide to the top of the cup and it should be 1.410" +/- .003. This is an important piece that does need adjusting over time and possibly replacement parts. See page 4 of your manual. There is a tiny set screw on the side to adjust/tighten for the exact height. You want this set perfectly as possible.
4. If you are certain you have checked to make certain all the individual parts look OK and the adjustment is correct, replace the assembly.
5. One more adjustment I recently found by contacting Dillons determines if the primer cup comes straight up into the shell plate or hits off to the side. To check this take everything off the shell plate, make certain it is tight and pull the handle down and watch the primer cup come up into the shell plate cut out in #2 position, priming. If it hits fore or aft, that can cause problems like I had. It can flip primers completely over and they can get stuck in the priming system, jamming things up. To fix this, pull the handle down and look at the priming system with a pen light and you will see a tiny allen screw. All this screw does is move the assembly fore and aft as needed. The problem with mine was I could adjust it and a couple hundred rounds later it was flipping primers again. I had an idea how to fix that additional problem and Dillon confirmed it, just used some blue Loctite.
While you are taking things apart, it goes without saying to look for stuck brass or powder in somewhere. If things got out of adjustment and were hitting off to the side, soft brass can be shaved off or metal can be chipped and is now under the primer cup.
I am now at the point where about once every year or year and a half, I take my priming system out and inspect, remeasure, clean and check for broken, worn or bent parts.
If this doesn't help, I am clueless. I tried. Holler if you have questions, I am getting decent about taking the SDB apart as I replaced several parts in mine and it down to individual parts, piece of cake once you get over the shaking and worrying about losing something! Blessings!
