Another trimming question.

[J E Custom]

On shawn's video he trimmed case's back till they got a full cut (squared). He did not mention that he trimmed all cases to the shortest length but, that may have been an over sight on his video. He did mention that he wasn't concerned that they were under recommended length as much as he wanted them squared and mentioned that after a few firings they would grow back out to intended length which leads me to believe that he would like to see them all at max length but more importantly squared. What say yal? Thank's, Brad

I have shot cases that were .040 thousandths shorter than the neck chamber (case length
may vary based on head space ) but the neck length needs to be the same case to case to
get consistant bullet grip.

Bullets are seated to the same overall lengths, so if the necks lengths are different, the bullet
to neck grip will be different.

The reason for trimming and turning is to make the bullet grip consistant and hopefully
lower Standard deviations.

If you trim the necks all the same and you have a few that still did not clean up the decision
then becomes whether to toss them or trim all the others to there length.

Some brass grows more than other based on pressure,design and work hardening, so I
recomend batching all brass and loading, shooting,sizing, trimming and annealing all of that
batch at the same time and the same number of times (Don't mix brass that has been fired
or sized a different number of times).

In this game "consistency" is the name of the game. At short distance these small things
don't have much impact on accuracy but they have a huge effect at extended distances
in my opinion.

J E CUSTOM

 

[Bullet bumper]

I absolutely disagree with notions about trimming excessively from chamber as a good action.
Yes, it contributes to carbon deposits, but worse and immediately with most cartridges, it increases ES.
This due to varying volume for gas, getting around case necks, that seal with differing timing.
If your shooting a hunting cartridge, and you really really want lower ES, you'll mind & manage your trim length, and neck tension, to reduce variances to your pressure peaks.

I shoot for under 5thou from chamber end. It's not always a choice with factory chambers, but it is with customs. My custom throats are also coaxial and tight(<.0005 over bullet).
With this, and turned necks, my neck soot extends maybe 1/8th" from mouths, and my ES gets into single digits.
That's consistent chamber sealing.

I don't believe anyone advised "excessive neck trimming"
You trim just enough to get them all square .
Interesting however I don't get any " neck soot at all on any cartridge I load for " and if you are getting 1/8 of neck soot you are doing something wrong . However it has little to do with neck length in general and would have more to do with neck to wall clearance and neck hardness compared to neck tensions and chamber pressure . Internal donuts can also contribute . Your bullet is getting well out before the case neck can seal properly . Sometimes increasing the powder load will fix it. Some people have the bullet seated so shallow and only a light load of powder that this happens .
Sometimes going to a slightly faster powder is better for the pressure , seating and neck tension conditions than the actual recommended powder .