SC_Dave said:
I loaded a few dummies and tried the push test on the scale. I could not push them back. I pushed to the point I was not willing to push anymore on the glass top bathroom scale.
As a point of reference I did the same with a factory round. Again, I pushed to the point I wasn't willing to push any harder.
Problem solved? I don't know. Problem created? I don't know.
Reloading should not be a guessing game and we use instruments capable of measuring thousandths of inch to help us do Quality Control checks.
I used to push on the bullet against the bench top to check for neck tension and bullet setback but not anymore.
Now, my QC check for neck tension/bullet setback is measuring the OAL/COL before and after feeding/chambering dummy rounds from the magazine as this better duplicates the forces involved when the slide slams the bullet nose against the feed ramp than simply pushing on the bullet with your finger (different people have different levels of strength and pain tolerance.
).
Finished rounds with good neck tension should not result in any bullet setback but I consider bullet setback up to around .003" acceptable and consider anything more than .005" to be an issue as bullet setback can increase chamber pressure and affect accuracy -
http://www.thehighroad.org/showthread.php?p=9639622#post9639622
QC step - Neck tension check:
I check for sufficient neck tension by measuring OAL before and after feeding/chambering the dummy rounds from the magazine and releasing the slide without riding it. After two chamberings, I did not measure any bullet setback so I rechambered five times. Guess what? No bullet setback! With many jacketed/plated bullets, I will experience some bullet setback after several chamberings but not with these bullets. Perhaps harder lead alloy (11-12 BHN) used as bullet core is not being squished to maintain greater neck tension? Out of curiosity, I chambered the 45ACP and 9mm rounds and I also did not measure bullet setback! This is really interesting and a very good thing if you have experienced neck tension/bullet setback issues.
As posted by many, neck tension comes from friction between resized case wall and the bullet base seated inside the case neck:
- Too much expander/flaring of case mouth will decrease neck tension
- Taper crimp does not increase neck tension and can actually decrease neck tension if used too much by reducing the bullet diameter while brass spring back pulls away from the bullet, reducing neck tension
- Neck tension will increase as bullet is seated deeper as case wall thickness increases towards case base. 115 gr FMJ/RN bullets with shorter bullet base often suffers from neck tension/bullet setback issues when seated longer and I prefer to load 115 gr FMJ/RN bullets shorter at 1.130"-1.135" instead of 1.160" I use with 115/124 gr FMJ/RN bullets to prevent powder charge compression.
- 9mm bullets come sized .355" - .356" for jacketed/plated bullets depending on manufacturer/bullet weight (some manufacturers size 115 gr plated RN bullets to .356" for greater neck tension, minimized bullet setback and greater accuracy).
- Using FCD with oversized bullets may reduce neck tension as post sizing of finished rounds will reduce bullet diameter but brass spring back will reduce friction between bullet base and case wall.
- Using plated bullets with harder bullet core will increase neck tension as harder core won't squish as much when bullet is seated and taper crimp applied. For this reason, RMR uses harder 11-12 BHN lead alloy with thicker plating and calls them "hardcore match". I have used various brand plated bullets over the decades and when I tested RMR HM bullets, my neck tension/bullet setback issues I had with other plated bullets essentially went away -
http://www.thehighroad.org/showthread.php?p=9620547#post9620547
bds said:
RMR said:
... harder lead core (11-12 BHN) than any plated bullet company that we know of.
I think some plated bullet manufacturers use softer swaged lead for bullet core. Perhaps the harder 11-12 BHN lead alloy maintains neck tension better when the bullet is seated and taper crimp applied instead of being squished? If that's the case, more consistent neck tension would produce more consistent chamber pressures.
More on neck tension / bullet setback issues:
http://www.thehighroad.org/showthread.php?p=9944402#post9944402
http://www.thehighroad.org/showthread.php?p=10121105#post10121105
http://www.thehighroad.org/showthread.php?p=10232332#post10232332
Dillon powder funnel expander 45 acp.
Dont know about "your" dies.
