Neck Tension and Seating Force - UPDATE

[NYDAN]

I have some progress to report.

First, I would like to apologize to sako2 who wrote, "NYDAN looking at your pictures I see copper shavings." I responded with "it must be an anomaly of the photographs. I closely inspected the loaded bullets and could not see any shavings." Apparently, the copper shavings had gotten wiped off the bullets between the time I photographed them and the time I inspected them based on sako2's comments. Later, when I was seating another set of bullets I did find copper savings. So, sako2's observations were correct and I was wrong.

I ordered additional expander mandrels from 21st Century Innovation. They offer expanders in increments of 0.0005" inches. I ordered 0.2635" and 0.2640" expanders. I ordered a VLD neck chamfering tool.

I had noted that after I had tumbled brass, the co-efficient of friction in the neck and primer pockets increased significantly. That was adding to the seating force required to seat the bullets.

So, after receiving the above mentioned, previously ordered honed seating stem. I did a few things:

• I switched to the 130 gr. Sierra Tipped Game King (Game Changer) bullet.
• I installed the custom honed seating stem in the seating die.
• I used the 0.2635" expander and expanded the necks again using graphite lubricant.
• I left any residual graphite from the secondary expanding operation in the case necks.

I loaded the last five cases I had (in that batch) and found that the neck tension dropped down to about 0.0013 to 0.0018 inches versus the 0.0026 to 0.0030 inches I used to get. Also, the seating force was greatly reduced. There were NO indentations on the bullets from the seating stem.

I shot the five cartridges and got the following results:



The average velocity had dropped quite a bit from where it had been.

Next, I had to perform brass prep on this lot of brass and am now shooting 4x fired, annealed, and tumbled brass.

I made an adjustment to powder charge and shot this target:


Next, I expanded directly from resizing using the 0.2635 expander and NOT using the 0.2627 expander at all.

My measurements indicate that the one step expansion resulted in a little less, AND MORE CONSISTENT, neck tension at 0.0012 to 0.0014 inches. This is my preferred method. I only the two step before because the necks had previously been expanded.

This morning, I shot this target:


This load seems to be shooting about a 0.5" group now.

 

[Charlie-NY]

Generally speaking - a pronounce ring on a bullet after seating is a sign of too much neck tension/interference. However, a mismatched seater stem will greatly exacerbate the problem.

A very simple solution for a mismatched seater is to chuck up a bullet in a drill and lightly cover it with ring lapping compound or similar honing compound. Then push it gently into the (removed) seater stem. Do this several times, replacing the honing compound as needed. Eventually, the seater will be much better mated to the ojive of the bullet. It is important to make sure that a pointy bullet is NOT bottoming out in the seater stem. If that's happening, the best solution is to buy a VLD stem and then hone as indicated.

 

[DrMike]

A thorough response, Dan.

 

[RL338]

I had noted that after I had tumbled brass, the co-efficient of friction in the neck and primer pockets increased significantly. That was adding to the seating force required to seat the bullets.

Bertram is one of the brass I run a brush thru the neck after wet tumbling to relieve the add “stick” before seating.

 

[JD338]

Great information Dan, thank you for sharing.

JD338

 

[longrangehunter]

Forster makes a great product Motor Mica for lubing the inside of the case neck. It works well and I’ve never experienced a problem with it in 25 years….. Powder contamination or grippy case necks that stick to the bullets over time.

It helps immensely when you wet tumble, or with new brass.

 

[sako2]

Dan no need for a apology.

 

[Darkhorse]

I have a simple method of dealing with the problem. I am mostly concerned that all my cases have the same or nearly the same amount of grip on the bullets.
First thing is prepping old cases. I chuck a drill bit in the drill press and wrap steel wool around it, turn on the drill and run the bit into the neck and move the case around until all the carbon, dirt, etc. is removed.
Next I size the cases, by sizing first I can feel those cases that feel tight and brittle, or harder than the normal feeling cases. These go into a container and the necks are later annealed and all of this lot go into a container.
Testing has shown getting all the case necks to equal hardness will bring in a lot of the flyers and really help to get those smaller groups.
When I size a case I can actually tell from feel which cases need annealing.
That's about as simple as it gets.

 

[wvbuckbuster]

Have you tried annealing before sizing?

 

[Darkhorse]

wvbuckbuster, Yes I've annealed before sizing and either one seems to work about equal. However if I size first I can tell which cases need annealing and which ones can wait another turn or so. That's the only reason I size first.