A couple of questions. How long are you waiting between shots and what is your ambient temp in which your shooting? If you have the capability to monitor barrel temp I would do so. The barrel temp can jump very surprising upwards once a soak time has been met. I noticed on my 6.5 CM that I shot last week, it took 5 shots to get some heat in the barrel. I could see the temp jump 5-10F after every shot if you waited for the temp to migrate through the steel. Putting a cooling fan on right after the shot and started cooling you could turn the cycle around in less than 5min. If you think it maybe temp sensitive, single shoot and cool between shoots. With a heavy barrel 0.9" OD you should be fine up to 20 shots without cooling. As far as bullet jump, I have found that Sierra like a bullet jump, not near the lands. I think this is pretty true with most of the ELD bullets since they have a longer bearing surface, and have no problem aligning. Have you checked to see if your getting any bullet jump in the magazine? How many do you load in a magazine for testing? I've found its better to just single load, which slows the shoot rate down. And keeps the heat away from the rounds in the magazine.
You may try a quick test to determine the best OAL for that round. Pick your best load then play with the length in 0.005" increments. Then use the best one for the rest of your testing. I normally use this test as last to fine tune, but since yours seams to be jumping around, may be worth the try.
As far as targets (dots). You mentioned that you have a hard time with the retitcle on your scope. Try going to the diamond targets which will help you align using the corners too. This works very well with heavy lined cross hairs. Also going to a black BE so you can't see your holes help on that 5th shot syndrome.
Does your upper have a adj gas block?
I have my 224V second test loaded and ready to shoot once I fine the time and when it's not scorching outside.
Note: I switched ISP this last week and can now view videos.
Your video is pretty good but a little winded.