Inconsistent sizing

[jelenko]

I'm getting about 3/1000's variation in headspace of resized LC 09 .223 cases.
This is happening in the same resizing die with the same case lube as .223 Winchester brass that is being resized with ~ +/- 0.5/1000's. For both types of brass I'm using grahpite for lubing the inside of the necks.
Generally, I've found variation in resized cases similar to the Winchester brass, including other years of LC.

I'm also seeing about 3/1000's variation in the headspace of these LC 09 cases after they are fired.

The RCBS precision case mic is used to measure the headspace.

Is anyone else seeing this type of variation in LC 09?

 

[snuffy]

1st, welcome to the high road forum.

3 thousandths from what? From your desired value, or from 0 or right on to 3 thou too long? That's the only time it would make for a problem is if it's too long, you could end up not chambering completely.

If for an AR platform, then it's desired to have free chambering rounds. If for a bolt rifle, a little resistance can be tolerated.

If you're thinking the LC '09 is a bit harder, hence springing back, then you might be right. Have I noticed it? No.

 

[rg1]

Firm pressure at the end of the stroke on every case plus I've used graphite or mica for lubing necks and find it not a good neck lube. I get much more consistent results using a RCBS nylon case neck brush. I simply spray one shot of Dillion's case lube on the brush and lube the inside necks. One squirt will lube several, maybe around 30 cases, before I spray the brush again. I suspect your expander ball is pulling the neck-shoulder forward on some cases. Polishing the expander ball helps some too. The RCBS case neck tool is simply the handle and you buy brushes for the caliber you're sizing. The brushes last a long time but I'd get a couple for each caliber.

 

[flashhole]

You might try annealing the brass to see if you get better consistency from your fire-formed rounds. Are you neck sizing only? If yes, you can't control shoulder bump and you simply live with what comes out of your gun. FL size the ones that are showing the greatest delta and see what you get.

 

[Ol` Joe]

I think what you are seeing is a variance in "springback" due to case wall thickness and/or work hardening. The die if properly set, should push the shoulder back a tad more then where you want it, and the case should then expand back out as the pressure is released to full in the over sizing.
Fireing a cartridge does the same thing in reverse. The case expands to fill the chamber then "shrinks" down a bit allowing it to be extracted. Work hardening or thicker walls will reduce the amount of memory the case has and cause the difference. Anealling may help

 

[Walkalong]

A .003 variance in where the shoulder ends up is not unusual at all with mixed brass. The harder brass springs back more while the dead soft brass stays put.

The LC 09 brass could be from different lots, just with the same head stamp. .003 isn't much.

If more people measured more brass, they would see it as well.

 

[jelenko]

Thanks to everyone for responding.

Walkalong - Good point. Even though the LC 09 was all new bought from Wiedners in 500 case bags, it might be from different production lots?
Since I've had enough experience with other lots of new brass being consistent [I reload about 5000 .223 rounds a year], I guess it must be cases from mixed lots.
I was assuming that since it was new and all in the same bag it would have been from the same production lot.

Snuffy - The variance I'm referring to is the difference between the cases with th smallest headspace and the cases with the largest headspace. My target is 2/1000 smaller than the fired case. Of course, in this case, since the fired brass also shows a 3/1000's variance, it's a bit of a problem to figure out where to set the resizing die to get 2/1000's 'set back'.

rg1 - FYI. I've used graphite for over 10,000 resizing's and have had the resized cases consistent within +/- 0.5/1000's - until now, of course. So, from my experience, the graphite has worked well.

 

[gamestalker]

I'm cursed with being unable to skip measuring and trimming all of my brass. A typical reloading session for 50 rounds of high powered for me can involve hours of work, bumping, trimming, weighing brass, cleaning primer pockets, and finding zero off the lands, and you name it, I do it.

 

[twofifty]

doing it all

^^^
Yet I'm sure you still end up with 2 or 3 thou variations in COL and even base-to-ogive on any given batch you have fussed over.

This is not to diss the quality of your attention to details, since + or - variation is in the very nature of everything, factory or hand-made.