Improper sizing die adjustment can cause grief. Here's an example...
Back in 1985, I bought my dad a Ruger M-77 RL in .250 Savage. That became his favorite firearm, except for one little problem: He could never manage to make reloads or handloads for it that would chamber correctly.
I opined on more than one occasion that the cause of his diffiuclty was an incorrectly adjusted sizing die. His response always involved telling me what I could do with my opinion, where I could take it, and that I shouldn't let the door hit me on the backside on my way to taking it there. After all, he had been handloading since 1973 for multiple calibers with no problems at all, he was an aircraft engineer so he wasn't mechanically inept like me, and he had been a pilot in Naval Aviation, so he didn't need some punk kid telling him a dang thing.
My dad isn't stupid and I always envied his mechanical aptitude. Heaven knows I relied on it a lot when wrenching on my Baja Bug as a kid, or when hotrodding cars later in life. And he always had a very systematic and logical approach to problem solving. His stubborn refusal to admit that he might maybe -just maybe- have misadjusted a sizing die perplexed me my whole life, and it still does today. He remains totally convinced that die adjustment had nothing to do with his problem.
This past Christmas, he re-gifted me that same rifle that he couldn't manage to load functional ammo for, and among other doo-dads he gave me, I also got his set of "defective" Lee Deluxe dies with collet neck resizer / decapper. Since getting the rifle home, I've reloaded ammo five times now using those same "defective" dies with no chambering or extraction problems at all.
I began reloading with those dies by disassembling them and cleaning them. Then, even though I had set up a set of Lee Deluxe dies for a .270 just a few months before, I read the instructions, and read through them as I went about setting up the decapper / sizer. They commence with words to the effect of: 'Begin by placing the appropriate shell holder, included with your die set, into the ram of your press" and from there, proper adjustment is indexed off contact between the die body and the shell holder.
My dad, who insists that he followed the directions "to the letter," skipped that part about inserting the "correct shell holder." His Dillon progressive press doesn't use that kind of shell holder, but uses an indexing shell plate instead, and he already had the .473" shell plate in the machine, so he moved on to the next step. Since he did not believe his die adjustment protocol to be in error, he did not read the part in the instructions that described the problem he had, the cause, and the solution. If you try to run a case through a Lee Collet Neck Sizer when the collet is stuck closed, or try to use it with the die body screwed into the press too far, the shoulder / body junction area of your case will enlarge slightly. On cases my dad sized that don't correctly chamber, that area is visibly burnished. Because he had indexed the die off the Dillon shell plate and not the supplied shell holder that he couldn't use on his press, and did so without factoring in a difference in height between the two parts, his die adjustment wound up being a full turn and a half too deep, each and every time, by following the REST of the directions to the letter.
He still doesn't believe this was the root of his problem all along -his die being incorrectly adjusted too deep in the press's tool head. He adjusted his Lee Collet Dies for his 'O6 by indexing adjustment off that same Dillon shell plate, and his '06 ammo "chambers fine." And it does in his Remington 742, that has a generous chamber, with a case lacking the degree of body taper the .250 Savage has. I shot some ammo he loaded out of my .30-'06 No.1 and all of it has a burnish at the shoulder / body junction that ammo I l've loaded from new or once fired cases on the same set of dies he used doesn't have.
If this story has a moral, it is that if your re-sized cases don't fit in the gun, or too readily accept a bullet without proper neck tension, don't be so proud as to assume that your sizer die is correctly adjusted. Before you make that call to the die manufactuer to complain about their shoddy product, double check your adjustment protocol. If it involves indexing off a position of die body contact with your shell holder, make sure any difference in shell holder height between the die maker's recommended shell holder and the one you are using is "factored in" to your adjustment scheme.
JP