Over the years, members sometimes perpetuate notions simply with something being "good or bad" without much explanation or based on decades old experience and information.
When I do "myth busting" threads, focus is made to either confirm or bust using objective, measurable, repeatable, factual data with more current lots and components (With
22LR misfire dud/no dud myth busting thread, decades old notion that some "cheap ammunition is junk" was busted as I achieved now going on 35,000 round testing with 99.9% primer ignition of 20+ brand/weight with blame going to rough shipping/handling of loose bulk ammo moving priming compound away from rim.)
With the "Neck tension and bullet setback" myth busting thread, several notions were addressed in achieving reloading consistency -
https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10712225
1. Case wall thickness consistency affecting finished roundness and dimensions of case neck / bulge - Measuring case wall thickness at 12/3/6/9 O'clock at .100"and .200" below case mouth demonstrated consistency of case wall thickness particularly at bullet base seating depth that bulged case neck to rub with chamber wall of tighter barrels. Inconsistency of case neck thickness can tolerance stack to produce oblong case neck (Not all bullets are perfectly round, especially if they are dropped/damaged during shipping). Since taper crimp is applied around .100" below case mouth, increasing taper crimp would not address case neck bulge .200" below case mouth.
So if you are using larger sized .356" diameter bullet and case neck is rubbing the chamber wall to prevent full chambering of finished rounds, using more consistent case wall thickness brass may resolve the case neck rubbing chamber wall issue.
2. Matching case wall thickness to diameter/seating depth of bullets - 9mm bullets come typically sized .354", .355" (Montana Gold, X-Treme, Precision Delta, Remington, Winchester, etc.), .3555" (Speer Gold Dot/TMJ, RMR, etc.) and .356" (Berry's, HSM, some HAP, some Zero, some Power Bond, lead/coated lead, etc.) -
https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453
If using smaller sized bullets, even using thicker case wall brass may allow finished rounds to fully chamber in tighter barrels. If using deeper bullet seating of 1.100" with FMJ/RN bullets or JHP/TC/FP bullets with deeper seated bullet base, using thinner case wall brass at case neck may allow finished rounds to fully chamber in tighter barrels.
3. Neck tension and bullet setback - It is not "finished OAL" that produce more consistent chamber pressures/muzzle velocities rather "chambered OAL" after bullet nose bumps the feed ramp and any subsequent bullet setback. I use feeding/chambering dummy rounds from the magazine as my QC check and to minimize or prevent bullet setback, I use thicker case wall brass.
The myth busting thread demonstrated using .354"/.355"/.3555"/.356" sized bullets which headstamp brass produced bullet setback and which brass did not with average bullet setback sorted in a final list when rounds were fed from magazines in Glock 22/23 using KKM/Lone Wolf conversion barrels.
So depending on the bullet sizing you use, you can reference the myth busting thread information to minimize/prevent bullet setback for your load development and powder work up to identify more accurate loads.
Enjoy and have fun.