"Rebounding" NATO 7.62 brass???

[scrmblr1982cj8]

I have a question about some of the NATO 7.62 brass I'm prepping for use.

About 10 years ago when I lived in South Carolina, I stocked up on used NATO 7.62 brass. Over the years, I've reloaded about 1k rounds for plinking and deer/hog hunting. None of these rounds were intended for long range use. I would resize and reload in the same sitting.

On Monday (1/23/23) I resized about 100 cases of PMJ 06' using my RCBS Rock Chucker Supreme with a RCBS .308 F L Die Set (P/N 15501). On every 10th case, I cycled in the chamber of a R700 .308 and in Wilson Case Gage. Each round fit perfectly in the Wilson Case Gage and cycled in the R700.

Last night (1/26/23), when prepping the mouths of the 100 cases, I noticed that while they cycle in the R700, they now do not fit as well in the Wilson Case Gage as they did 3 nights before.

In reading from several sources later last night and earlier today, I read about a few potential causes: ( 1 ) "rebounding" if I don't hold the cases for 5-6 seconds per cycle, and ( 2 ) the possible need for small base die.

I noticed a crack in the toggle block (replacements parts are on the way) so my Rock Chucker is currently disassembled and can't try resizing currently.

Anyone with experience reloading NATO 7.62 brass willing to chime in?

Thanks,

Scrmblr1982cj8

 

[ARlife4me]

I have RP and WCC mainly. I've deprimed, cleaned and FL sized, but haven't reloaded any yet. Deprimed on a Hornady APP w/universal decapping die and resized on a 550 (Dillon die). No issues so far.

 

[Dmagna]

How many reloads do you have on the cases?

 

[Laelkhunter]

By prepping, if you mean you trimmed (the length), it's possible you did not chamfer the outside of the case mouth, or didn't chamfer enough.

 

[ARlife4me]

How many reloads do you have on the cases?

Zero. I could run a few thru and check?

 

[ARlife4me]

So, it's a neck issue or chamber issue?

I only load for AR10's and run die down until it touches the case holder/case plate. And no I don't have small base dies if you're going to ask. Crazy it's doing this in a bolt gun?

 

[scrmblr1982cj8]

No reloads on the brass. These are my initial resizings. I deprimed, cleaned, and used a Giraud to chamfer the mouth. I'll redo the setup on the Rock Chucker once they send me a new toggle block.

 

[Critter Picker]

Did you trim? I've had a 308 with a tight chamber and if you have bright spots on the case mouth (from touching the chamber)

Do you feel drag on bolt handle when closing bolt?

Case neck too thick?

 

[338 dude]

No reloads on the brass. These are my initial resizings. I deprimed, cleaned, and used a Giraud to chamfer the mouth. I'll redo the setup on the Rock Chucker once they send me a new toggle block.

Dwell time is very important. I always pause just a few seconds with the case completely up in the die .

 

[can1010]

with military brass i always anneal before sizing, you just dont know what chamber or how sloppy the chamber was on the weapon it was shot out of.
i have used plenty of LC and WCC over the years and annealing first was the ticket.

 

[BillLarson]

I have shot 1000`s of LC97....... never a problem.....

 

[Rflshootr]

Last night (1/26/23), when prepping the mouths of the 100 cases, I noticed that while they cycle in the R700, they now do not fit as well in the Wilson Case Gage as they did 3 nights before.

Elaborate on "do not fit as well" please.

 

[VinceMule]

OP, the answer lies in some understanding of metallurgy.

The Military brass was likely fired in a machine gun with a large chamber. The brass swelled out upon firing.

Now, you some years later sized the brass down to a smaller size. Over time, the brass starts to "normalize" or "spring back" swelling back out, trying to reach that first chamber dimension.

We size with a Small base sizer to allow for this kind of "normalizing or spring back".

Success comes in keeping the ammo "fresh" with that kind of brass.

Annealing prior to sizing helps in the neck and to some degree the shoulder, but not the web area.

Also, after decapping the brass, I check for off-center flash holes. I have had lots of LC that were terrible in this regard. I hold up a hand full at a time, examining under bright light.

I always sort by year on LC brass as it does vary considerably, and if you are looking for 1/2" groups or less, this is a critical issue.

 

[Revolting Peasant]

I have reloaded lots of NATO brass. Never had the issue you are describing. I have read that brass can not only work harden, but can also "age harden". I have reloaded old brass several times and lost lots due to cracks, so there may be something to this. It may affect how the brass handles resizing as well.
I would resize some more and watch it, now that you suspect a problem. If further research proves it is an issue, probably going to have to anneal if you want to save the brass.