Rough Rust-like finish inside alpha brass necks

[JRBullock1987]

Does anyone get this rough, rust-like finish and color inside their brass neck after firing/cleaning/resizing? I loaded up some 6.5cm rounds after one firing. Dry media cleaned. Resized with sac die (.003" neck tension). and they were extremely heavy seating force and inconsistent seating depths with my l.e. wilson so i looked inside the necks and saw this. Any way to avoid this? I ended up having to use some dry neck lube (graphite) to help with lowering the seating force to feel normal and get my seating depth consistent. Didn't have any issues with the new brass (alpha munitions ocd LRP). This was after one firing. Any one deal with this or have a solution to prevent this?
Thanks,

 

[918v]

It’s probably galling. Use a bigger expander and graphite to lower the seating pressure, and/or tumble in corn con and nufinish.

 

[Dolomite]

It’s the opposite, you still had carbon inside the neck and the mandrel removed the carbon to expose the brass under it.

 

[Rocketmandb]

Use some neck lube.

 

[Edsel]

It’s the opposite, you still had carbon inside the neck and the mandrel removed the carbon to expose the brass under it.

This explains the appearance of the necks.

Very typical finding after neck dilation with a mandrel.

 

[OREGUN]

A bunch of questions: What do you mean by “dry media cleaned”? Is there any lube being applied to the inside of the neck or the “expanding” part of the sizing die (mandrel or expander ball, whatever)? And what is that exactly? You said sac die. Does that include the integral expander mandrel? Are you mandrelling in a separate step? I’m not sure what the sac options are I’ve only used their combined decapping expander mandrel.

Generally speaking, try spraying your sizing lube across the case mouths so that some gets into the case mouth. Apply some kind of lubrication to your sizing mandrel (imperial die wax). That usually does it for me (makes it such that I don’t lube my cases before seating). Regarding cleaning, think about how you are cleaning and what it means for carbon in the neck. I anneal and then tumble for 2 hours in Lyman’s media with no additives (the green one) and then size. I like a bit of carbon left in the necks. If you are aggressively cleaning, cleaning again after sizing, or annealing immediately before sizing, you are changing the condition in the neck and can get less lubricity than you want from the carbon that remains…thus requiring some kind of seating lube.

 

[Rocketmandb]

Also @JRBullock1987 are you lubing before you mandrel?

 

[JRBullock1987]

im using expander mandrel in the same step as sizing with the sac die. I use imperial sizing die wax inside the neck as well as outside of case. I use corn cob media for about an hour. Then after I resize i clean again for about 15 to 20 minutes

 

[Cascade Hemi]

NeoLube is the way.

 

[OREGUN]

im using expander mandrel in the same step as sizing with the sac die. I use imperial sizing die wax inside the neck as well as outside of case. I use corn cob media for about an hour. Then after I resize i clean again for about 15 to 20 minutes

Skip the after-sizing tumble. That’s the source of your trouble. Try a few that you just wipe the die wax off the outside of the case with a paper towel and swirl around the inside of the neck with a cotton swab…not trying to wipe it out, just distribute the leftover lube so kernels of powder don’t stick in it. Honestly you could skip the cotton swab step and it wont make a difference.

If that works, it’s too time consuming to physically wipe off each case after sizing if you’re doing more than a couple dozen. If so, try throwing your cases in an open topped container and spraying generously with acetone. Let it flash off and the lube goes with it but in my experience it doesn’t take the lube out of the necks. I get the same results as if I just wiped them off (no lube outside but a smooth seating process) but I can de-lube 200 cases in a couple of minutes.

The other option is to re-lube your case necks with something before seating.

 

[JRBullock1987]

Skip the after-sizing tumble. That’s the source of your trouble. Try a few that you just wipe the die wax off the outside of the case with a paper towel and swirl around the inside of the neck with a cotton swab…not trying to wipe it out, just distribute the leftover lube so kernels of powder don’t stick in it. Honestly you could skip the cotton swab step and it wont make a difference.

If that works, it’s too time consuming to physically wipe off each case after sizing if you’re doing more than a couple dozen. If so, try throwing your cases in an open topped container and spraying generously with acetone. Let it flash off and the lube goes with it but in my experience it doesn’t take the lube out of the necks. I get the same results as if I just wiped them off (no lube outside but a smooth seating process) but I can de-lube 200 cases in a couple of minutes.

The other option is to re-lube your case necks with something before seating.

Thanks for the info. I actually tried using dry neck lube and that helped a ton to get it seating smoother and more consistent. I'll have to try what you suggested. Thanks bro.