6PPC THIS IS STRANGE

[Nick Caprinolo]

The other day, I loaded up 50 rounds with powder. I attempted to insert 68gr Barts bullets and crushed several case necks. When I say crush, I mean just that. These cases have been reloaded at least 10 times.

I made some measurements, and found that the case necks had become thick by at least .002 and some .003. Barrel is a 262 neck and these cases were turned to .0075 bullets. I should be seeing a formed case with a .258 neck and after bullet insertion .260.

I have never had a case where the neck thicken before this. I trimmed then down to .0075 and everything seems good.

Question is why and how did this come about.

 

[JEFFPPC]

Brass flows forward.....case length grows......and gets thicker. Common sense but most ignore it. If you shoot tight necks with minimal clearance like I do you learn. About every 5 firings I run the neck wall trimmer down the necks. Some you get some very fine powder. Others, you will say, Holy cow, where did that come from. If you value seating uniformity and consistent ES, it plays a big part in achieving and maintaining both in my experience.

 

[Nick Caprinolo]

Brass flows forward.....case length grows......and gets thicker. Common sense but most ignore it. If you shoot tight necks with minimal clearance like I do you learn. About every 5 firings I run the neck wall trimmer down the necks. Some you get some very fine powder. Others, you will say, Holy cow, where did that come from. If you value seating conformity and consistent ES, it plays a big part in achieving and maintaining both in my experience.

That does make a lot of sense. I just never had a problem until now. It is good to know that this is a normal occurrence. I will keep an eye on this from now on. I will be getting some new Lapua shortly and start anew.

 

[rwj]

Brass flows forward.....case length grows......and gets thicker. Common sense but most ignore it. If you shoot tight necks with minimal clearance like I do you learn. About every 5 firings I run the neck wall trimmer down the necks. Some you get some very fine powder. Others, you will say, Holy cow, where did that come from. If you value seating uniformity and consistent ES, it plays a big part in achieving and maintaining both in my experience.

Is this something unique to the 6PPC? I’m shooting a 6BR with necks turned to ~.012” thick and have yet to note any significant change in neck wall thickness after many firing cycles. The ammunition is admittedly tuned for the low velocity/pressure nodes.

 

[tsyarnall]

Nick, seems like I saw where you were needing brass. Did you find any?

 

[snert]

Brass flows differently in different cases, brandes, pressures. But it flows. Length and thickness. It just shows up in tight necks, well, because they are tight.

 

[Nick Caprinolo]

Nick, seems like I saw where you were needing brass. Did you find any?

I did, Thanks for asking.

 

[PopCharlie]

Just found this in my Lapua 6br brass. I originally turned them to .010 for a .266 neck. Loaded rounds were .263 to .2635. After firing them 7 times, I re-checked. I needed to turn them again to .010. I also turned 25 pcs originally turned to .010, fired 10 times, down to .009.
PopCharlie

 

[JEFFPPC]

Is this something unique to the 6PPC? I’m shooting a 6BR with necks turned to ~.012” thick and have yet to note any significant change in neck wall thickness after many firing cycles. The ammunition is admittedly tuned for the low velocity/pressure nodes.

No, it happens with all cartridges. If your shooting custom necks with minimal clearance its important. If your shooting long range it will effect es.

 

[mikecr]

It depends on case design and your sizing.
A 6PPC is not an improved cartridge, it's run at very high pressures normally, and normally FL sized considerably.
A lot of sizing will move thickness up into necks.

If you were shooting something like a 6Dasher and using minimally sizing custom dies, you should not see a bit of neck thickness change.
I have never seen brass 'flow'. Instead, I see brass stretching, and brass moved with sizing. When neither is allowed, it doesn't change.