I have seen this question asked a few times. Ok so I just did an experiment. I took 4 .223 cases same lot federal head stamp. These spent many hours in walnut media they have been fired once.. so really clean and i decided to anneal 2 before case sizing and 2 after case sizing. After I annealed the first 2 cases i full length sized them and used hornady unique case lube in the tub. I then cleaned off the case lube inside and out 3 times with clean rag and Q tips. Then brush the inside of the neck with 30 cal bore brush. then Q tip inside again 2 times. I then sized the other 2 cases and removed all the sizing wax as the above was done but NO neck brushing with bore brush. I then annealed those 2 cases. The neck ID is now carburized and feels very rough and the ID has shrunk just a hair from the carburization. I brushed the neck ID and this is now smooth again. I cleaned the case neck inside 2 times with a Q tip after the brushing. All 4 cases have .221" ID. Bullet seating time. I have some Boat tail tipped match kings and measured the OD and all 4 came to .2245" The cases that were annealed then resized showed 40 PSI to seat the bullet and this 40 was a constant the entire time during seating to the full length of the bearing surface. The bearing surface is more than .100" below the neck.. pressure was constant. The case that was sized then annealed measured 40 psi to seat the bullet but as you continued seating the bullet pressure dropped on the gauge to 20 psi. I only seated 1 of each with the gauge. As i do it in vise to measure the pressure. I found this strange that it (seating pressure) dropped during seating. So the next 2 cases one annealed before and one annealed after sizing went to the loading bench. I seated a bullet into each case.. the case that was annealed before sizing had the same pressure the entire seating distance. The case that was annealed after sizing mimicked what was shown to happen on the gauge. Initial seating pressure was high and felt like the above case then it relaxed and felt really easy to seat the bullet. Yes there are many ways to do it. I always anneal then size. BUT AFTER Annealing I brush my case necks inside.. carburization is rough , I do not like rough cases poked into my dies. Take your calipers and measure the ID of the case.. while measuring with slight pressure on the measure slowly spin the case in your hand.. you can feel the surface texture of the case. I find excellent accuracy in smooth and round case necks.. brushing has shrunk my groups in every case i load. Try the caliper thing to feel roughness in the necks.