Newbie Question on Measurements after Sizing and Seating 6.5 Creedmoor

[mjl650]

Sorry if this has been asked before but after searching I haven't been able to come up with an answer.
I'm reloading once fired Hornady brass(from a different 6.5CM) and full length sizing with a Redding type S die using a Forster Co-Ax press. Sizing to .002" below measurements from once fired brass from my 6.5. With the die adjusted I'm getting readings from .001" below to .0005" above my target number. Also when seating Hornady 120gr ELD-M bullets for COAL with a Redding Competition Micrometer die the same thing is happening. Also all the cases are trimmed to the same length. Is this to be expected or am I doing something wrong?

 

[lawman29]

Describe in more detail how you're measuring and the tools you're using to do it.

Search under "shoulder bump" lots of info.

For seating depth you measure from the ogive not the tip.

 

[mikecr]

Sizing to .002" below measurements

What 'measurements'?

 

[Dusty Stevens]

Take the same measurement a few times maybe over a day and see if you can get consistent. Write it on the case with a sharpie. Are you using a compressed load? Hold your sizing at the top for 5 seconds and see if it helps. In the end the main thing you gotta ask is does it matter?

 

[mjl650]

Describe in more detail how you're measuring and the tools you're using to do it.

Search under "shoulder bump" lots of info.

For seating depth you measure from the ogive not the tip.

Thanks for the input so far. Let me try to clarify a little more.
I'm checking the headspace on a once fired case from my rifle with a Hornady LNL Headspace gauge with the C375 bushing. It's mounted on Mitutoyo Digital Calipers. As an example...... when measuring the once fired brass I'm getting a pretty consistent reading of 1.5560" on the calipers. I set my sizing die trying to get a reading of 1.5540" after sizing the cases but I can't get them all to come out the same. The range I'm getting is from 1.5535" to 1.555", all the cases will chamber in the gun and fall within spec when checked with a Wilson Headspace gauge. What I'm asking is does that difference in the sizing going to significantly affect accuracy?

As for seating depth I've been measuring tip so I got that wrong.

 

[mjl650]

Take the same measurement a few times maybe over a day and see if you can get consistent. Write it on the case with a sharpie. Are you using a compressed load? Hold your sizing at the top for 5 seconds and see if it helps. In the end the main thing you gotta ask is does it matter?

I didn't hold the sizing die at the top for any length of time, I'll have to do that for the next batch.
Does it matter to me......yes, I'm anal by nature. Also I'm presently doing better with factory ammo than with reloads and I need to reverse that situation in order to justify reloading my own ammo. I am enjoying reloading my ammo though.

 

[Deleted old_dood]

you shouldn't bump the shoulder back until it's been fully fire formed in your rifle. You said the brass was 1X fired in a different rifle. Fire them in your rifle until the brass exhibits some resistance to bolt closing then worry about bumping the shoulder.

 

[ckaberna]

What “old dood” said. And think about this, your trying to measure to the .0005, all the brass is not the same “hardness” so it will not be perfect and set back the same. If you strive for that, take all the longer ones and run your die down another 1/4-1/3 of a turn and resize the longer ones until they match the shorter ones. Before I did all that, load 10 of your shortest and 10 of the longest and shoot to see what difference there is. I would bet you cannot see enough difference to worry about.

 

[David Christian]

@mjl650, I have 2 thoughts for you that both relate to your resizing step. 1. Have you thoroughly cleaned out your die? 2. Do you notice any slop in your press related to where the cartridge base seats into your press?

 

[Dusty Stevens]

Ive found on the coax to be more consistent use the shellholder conversion instead of the sliding plates

 

[JFrank]

I didn't hold the sizing die at the top for any length of time, I'll have to do that for the next batch.
Does it matter to me......yes, I'm anal by nature. Also I'm presently doing better with factory ammo than with reloads and I need to reverse that situation in order to justify reloading my own ammo. I am enjoying reloading my ammo though.

No worries
Your already on your way to more accurate rounds.

 

[MikeMcCasland]

Holding a perfect .001 or .0005 bump across 100 pieces of brass happens a lot on the internet.

It happens pretty rarely for me in real life, and I'm talking same lot, same number of firings, press setup perfectly, annealed prior etc.

I wouldn't worry about a .0015 ES in your shoulder bump.