Shoulder Bump Inconsistency ( 6.5CM Nosler )

[lead.flyer]

I recently revisited what my Forster (non bushing) full length resizing die was doing to my shoulders..... what I discovered surprised me. I used Hornady's Headspace kit for measurement.

The "Cliff Notes" version -- On a population of 140 pieces of brass I found .009" overall shoulder variance on 5X fired brass.{annealed after 4th and 5th firing}
- this surprised me.

I took the longest pieces and found that anything longer than 3.5645" was hard to chamber and adjusted my Forster die accordingly. Post die adjustment some shoulders were set back to the desired measurement of 3.564 and some were set .002" below that (3.562").

??? Has anyone else experienced variance in shoulder set back
-- given a consistent die setting
??? Shouldn't shoulders be set consistently or does work hardness (or some other factor) come into play?



additional data:
Unfired shoulder meas. = 3.558"-3.559" ( 10 pieces unfired Nosler brass )

Fired shoulder meas. (140 population):
3.553-3.559" ( ~10 pieces)
3.362" ( 12 pieces )
3.363" ( ~50 pieces )
3.364" ( ~55 pieces )
3.365" ( ~20 pieces )

equipment:
RCBS RockChucker press
Forser FL (non-bushing) Resier
Nosler 6.5CM brass

annealed after 4th and 5th firing

does any of this make sense?

TIA,
brian

[bsumoba]

work hardened brass, brass springback, variations in the brass material composition...they all play a factor.

I get fairly consistent fired shoulder measurements in all my bolt action rifles. I use Lapua brass and they are all the same lot #.

If you are using a semi-auto rifle, there could be a chance that brass is expanding or contracting differently as it gets essentially ripped out of the chamber shortly after being touched off.

Nosler brass from my understanding, is also sorted by weight. This may pose a problem if different lot#'s of brass are combined in a batch and sorted by weight that way.

[ditchdigger]

Do you have a carbide expander?

Do you use dry lube on the inside/outside of the case neck?

The brass could be stretching back a little bit.

[lead.flyer]

much thanks for the responses.

my nosler brass is from a singular lot and all cases are on the same shot count.
they're only shot in one bolt action chamber.

i think i tracked it down to work hardness. i took the longer than desired cases and ran them back through the resizer (multiple times required for some cases) but ultimately got them close to where i want them.

as i am newerish (~2yrs) to reloading i was surprised to "learn" that just because you put brass through the resizer it doesn't necessarily guarantee the shoulders are reset to desired spec. i guess i need to add some more measurement steps into my process.

[fguffey]

does any of this make sense?

I am sure it makes sense to everyone else but it makes no sense to me.

I have 8 Remington Mag cases and dies that has a shoulder case body juncture that is 2.389 from the case head and you have 6.5 CM cases with a distance from the shoulder to the case head that is 3.558".

You could be talking about the maximum overall length from the top of the bullet to the case head. And then there is that thing with bump, bump sounds like an accident and I find bumping is impossible to do when it comes to the shoulder of the case.

Reloaders believe they can move the shoulder; I always want to ask, "How do you do that?" If they understood they would answer the question, instead of answering the question they get angry.

F. Guffey

additional data:
Unfired shoulder meas. = 3.558"-3.559" ( 10 pieces unfired Nosler brass )

[bigdawg86]

Are you running the cases up in the die with a hard cam over? Consider getting the Redding Competition shell holder set. It allows you to set shoulder bump from +0.010 to +.0.002

That would possibly allow a hard bump to ensure more uniform sizing depending on your dies.

I purchased that for my Whidden Gunworks dies, but found that they have a shorter die than others... so even with the +.010 shell holder and a hard bump the brass is sized too small.

[fguffey]

Are you running the cases up in the die with a hard cam over? Consider getting the Redding Competition shell holder set. It allows you to set shoulder bump from +0.010 to +.0.002

That would possibly allow a hard bump to ensure more uniform sizing depending on your dies.

I purchased that for my Whidden Gunworks dies, but found that they have a shorter die than others... so even with the +.010 shell holder and a hard bump the brass is sized too small.

I am not going to say I need my money back but I do have a #6 Redding competition shell holder set; my set is designed to increase the length of the case from the shoulder to the case head. I do not use the set but I have it JIC (just in case).

Before that I used the feeler gage when adjusting the die off of the shell holder. I have the advantage; with a feeler gage set I can adjust the die off the shell holder from .001" to infinity or a more particles .016".

And then there is shortening the case from the shoulder to the case head beyond minimum length Full length sized. For me that is not a problem because I use the same feeler gage when sizing cases for short chambers. I place the feeler gage between the deck of the shell holder and case head. The feeler gage raises the case off of the deck of the shell holder; doing so increases the presses ability to overcome the cases ability to resist sizing.

I paid $5.00 for the # 6 Redding competition shell holder set. Not a problem for me but three of them are off by .001" each. And then there is the cam over? I have three Rock Chuckers; I do not have a Rock Checker that cams over. I have 12 Herter presses, all of my Herter presses cam over, all of my cam over presses were referred to as being bump presses because they all 'bump'.

F. Guffey