Sounds like a carbon ring.I’ve had a interesting go with my 22 creedmoor and the 88gr Hornady eldm. I used RL26 almost exclusively and found it to be a little bit touchy. The powder seemed to build up pressure for no apparent reason. I had a great .25 moa load at 41 gr but after about 50rds the velocity jumped 100fps and the bolt started getting sticky and I had to drop the load a full grain. It kept doing that to me and I stopped shooting it because of that. I did try h4350 in a ladder test and it seemed to have promising results. I don’t trust RL26 anymore because of this. Others have experienced the same thing saying it builds up a carbon ring in the barrel. I can’t confirm that, but it was continually going up in pressure.