Why do you neck turn ?
if loaded and fired are the SAME, you have a really tight chamber and your cases need necks turned.Well I'm shooting a 6/284 . Neck of loaded round is .275 neck of fired case is .275 plus I'm getting tough extraction and pressure signs so it must be things are too tight.
It's usually safe to assume about .001 springback after firing. Meaning a .276 chamber neck will give .275 fired case necks. If loaded rounds are .275 then you've maybe only got .001 clearance or .0005" all the way around the loaded neck/bullet before it's fired.
In a stricly competition gun that is kept squeaky clean, that would maybe work if you didn't want to resize cases......fitted neck gun is the term I've heard........I bet you need a press to seat bullets (without sizing first)...... they probably wont seat with your fingers??
If that's the case, and it's a hunting gun that might get a little dirty between cleanings, I'd clean up (or turn down) the necks a little. Shouldn't take much, maybe .0005 to .0008 off the current neck thickness. Whatever you take off will be double by time you go full circle. After you turn necks, the tension on a loaded round will decrease unless you change bushing size in the resize die. You may have a tight enough bushing or die neck already, so this might not apply in your case.
If you dont want to turn the necks, a gunsmith can sometimes ream out the chamber neck just a touch. Or, you could try a different brand of brass that has thinner necks to begin with. If you've never turned necks, you can be in for quite a little expense with expander mandrels, turning mandrels, power case drivers, case holders, neck turner and cutters, tubing or neck thickness micrometers, ect. They are all necessary to turn a high volume of cases to within tight tolerances.
Sinclair International is a great place to get neck turning equipment IMO. Most of the customer service people know what they are talking about and are very helpful.
Just my opinion, but most rifles that are capable, don't need neck turning for 1/2 MOA groups, 1/2 minute and even better should come easy with good rifles and decent handloads/load development. But.........If we are after sub 1/4 MOA and better all the time, that's when we take off the high spots, or get tight neck chambers and turn down brass.
I have a gun with a fitted chamber(not just necks).
26wssm imp, chamber nk: .291, I turn necks to 13thou thick: .290 loaded.
My fired necks spring back to .289, and I lightly partial NS using a Wilson & .288 bushing for tension that worked out from load development.
I'd say it's fitted necks in that I don't have to resize them(didn't for ~5-6 reloads).
Also, this is a 16.5lb BR gun that is kept in pristine condition.
No way to say what my dimensions contribute to precision, but it's even easier to reload than a 223 or 6br, and easily shoots 1/4moa grouping to 300yds w/139Laps at 3025fps.
I didn't go tightneck for accuracy in the short term, but for accuracy in the long term.
I could do this. If I had an enclosure for my RCBS CM, I could go to the range with a single case, shoot all day, & it wouldn't slow me a bit.Ron Pence used to have a 6BR (or 6PPC) that the neck and chamber were fitted very tight. He never resized a case, and literally seated the next bullet in a once fired case untouched except for priming. gary