Sizing inconsistency

[eod.tek]

I'm trying to track down what is going on with some irregularity in my resizing process.
I have a bullet central sizing die for my 300 Norma, I'm using a redding t7, I set my die up to the headspace I'm looking for (until my bolt closes freely with the sized brass, about 3 thousandths), lock it down, use Hornady case lube, and sized 100 pieces of brass. 90 of those pieces are within a half thousandth to a thou of each other, but 10 pieces were three thousandths shorter than the shortest of the rest of them. Those 10 pieces are around 6-8 thousandths shorter than fired brass.

Is there anything obvious that I should be looking for causing this? I generally like to test the first few pieces and then just keep moving with my process, but this is giving me trust issues lol.

Also, if you ever end up with sized brass smaller than your normal batch size, do you just use it as a fouler or do you send them? I don't think that an extra 3 thou will make this giant difference, but, it is an inconsistentcy that I feel like I can control.

 

[Lawnboi]

How many times fired? It can take a few firings to reach your chamber dimension.

Die contacting the shell holder is also a big deal with sizing. I use Redding comp shell holders to set headspace

 

[eod.tek]

It's on its 6th firing, and they all are very consistent size before sizing so I'm pretty sure they're filling the chamber.
I have looked at that set before, I may have to take a look again

 

[Lawnboi]

Are you annealing?

 

[eod.tek]

Are you annealing?

Yeah, with a flame annealer setup on 10 pieces of gear brass I've set aside just for adjusting it each time.

 

[Wapiti1]

Annealing was my question. Do you anneal every reload?

I would suspect a few pieces are annealed a bit more than the others. Weigh them compared to the others and see if they are a little lighter. Could be a slightly thinner case shoulder/neck that annealed differently. Also can seat a bullet in them and measure the case neck and compare to see if there is a thickness difference. Are they all from the same lot of brass, or different manufacturing lots?

One other possibility is cleanliness. Bright brass anneals slower than stained or soot coated brass due to it being more reflective.

Just a few thoughts.

Jeremy

 

[Carl Ross]

If I measure enough samples (at least 30-50) I’ve found I always have .002” variation between my high and low shoulder datum no matter what I’ve tried. Now I just accept it. Possibly a good induction annealer and a crazy stiff press could improve things, but I like my system and am happy with the results.

I will say I’ve not been annealing recently, as I think I induce variability with my flame annealer and it’s definitely an optional step. If you’re moving brass a minimal amount (bumping shoulders to .002” under chamber dimension, using a bushing die or honed die) you are work hardening cases at a pretty slow rate. But…if someone donated an AMP to me I’d definitely give it a whirl

You can spend a lot of time and money on reloading equipment and processes, but lots of them can’t be discerned down range for 99% of applications.

 

[eod.tek]

If I measure enough samples (at least 30-50) I’ve found I always have .002” variation between my high and low shoulder datum no matter what I’ve tried. Now I just accept it. Possibly a good induction annealer and a crazy stiff press could improve things, but I like my system and am happy with the results.

I will say I’ve not been annealing recently, as I think I induce variability with my flame annealer and it’s definitely an optional step. If you’re moving brass a minimal amount (bumping shoulders to .002” under chamber dimension, using a bushing die or honed die) you are work hardening cases at a pretty slow rate. But…if someone donated an AMP to me I’d definitely give it a whirl

You can spend a lot of time and money on reloading equipment and processes, but lots of them can’t be discerned down range for 99% of applications.

Yeah, I think there's is probably some variation in annealing. I think I may try a pressure regulator and see if I can keep it more consistent.
I wouldn't be as worried about annealing if 300 Norma brass was as readily available as say Creedmoor is.

If you ever find someone giving away amps to try, let me know, I'd like to get in on that!

 

[TaperPin]

I’ve had your issue in the back of my mind all week. Since your issue is a handful of shorter lengths, rather than general variability, it could be die contamination - too much lube has made its way up on the shoulder, but not enough to show denting. A .003” layer of lube across an entire shoulder with nowhere to go could easily push the shoulder back. It would be easy to test - just clean the die, go light on the lube and see if the issue goes away.