Home Forums Reloading Big Game Rifles Need some advice…

In 20 years of reloading, I had my first instance of case head separation on extraction and badly flattened/blown primers. I know what it means, but I’m unable to diagnose it.

Rifle was a new Tikka T3 Superlite in .30-06. 57.5 grains H4350, 165 Accubond, WLR primers, new Nosler brass (new lot). This combo had been fired a number of times in this rifle without issue, always in colder temps (including this time). After the incident, I pulled the loaded rounds and verified charge, etc. doesn’t appear to have been an error on my part.

What was different this time was that when I initially sized the new brass, it appeared to be minimally sized or even undersized compared to previous lots. Is it possible that my load is close to max for this chamber, and the smaller case volume simply pushed case pressures over the edge and stretched case length past the breaking point for a couple of pieces? 57.5g H4350 and a 165 is a classic combo in the ‘06, but Nosler does list it as a max charge.

It's a max charge according to Nosler. I'd be a little leery of it, especially if you switched lots of powder. You didn't state if you did that, or if you have been using the same old 8 pound keg for years in that rifle. If it were me, I'd measure from the datum point of the shoulder to the base and check that against your fireformed brass (chamber of your rifle). Since it's a new lot of brass, I'd also be suspect of that. If the brass is way undersized right out of the box, I'd contact Nosler. It's probably a new brass/lot issue.

I've never heard of case head separation on new brass. You must have been way overpressure. Are you SURE you loaded the correct powder? Was the bullet jammed into the lands? Bore obstruction? Have you checked the inside of the new brass with a paperclip? How hard was the bolt lift - did you need a mallet to open it?
Oh, and glad you were not hurt.

Like BSA suggested, I would check the datum on the new brass and compare that to a fired piece. If the shoulder was way way too short I guess you could have stretched the brass enough on the first firing to separate the head. That would also explain the flattened primer , but not the blown primer. What did the failed primer look like? Perforated at the firing pin strike, blown out the side? Any pictures of the case you can share?

I've had this happen when I over sized new brass using a custom die. The excessive headspace resulted in some casehead separations, flattened primers. It looked like an overmax load, but was my standard load that I'd used before. The only "delta" was pushing the shoulders back too far.

Due to the fact new brass is made undersized to fit 99% of the rifles that chambered for it, I never resize new brass. Can cause problems. Maybe neck size, but never full length. First firing I back off max 1/2 grain and fire form. Have also been known to COW it in the garage.

A FL sizing die will never even hit the shoulder of a new piece of brass. Again, where you get your info from is the question I have to ask.. You are swinging and missing a lot these days swifty..

Almost never, but I have run into new brass that needed a bump

Pot meet kettle........lol

Man you be going to get the nickname of twiglette.

If new brass is not undersized why is it that SAMMI max on the brass is 3 thou shorter at the headspace datum point than the SAMMI minimum chamber dimension to the same datum point?

Only problem I ever had with new brass was with Nosler. It had minimum dimension primer pockets that would not except federal primers. Your situation seems to be excessive headspace, whether because of the new brass or being bumped . Double check all the nosler brass and proceed with it with caution .

IME case head separation comes from headspace issues not over pressure unless you have set back the lugs which results in headspace issues. To put it more simply, you have a headspace issue.

If you are loading to the max and shooting in warmer weather than that changes everything with a NON temp resistant powder.

Like others have said, I'd bet your brass has the shoulder too far back for your chamber creating a headspace issue, might just be a case of tolerance stacking. I suggest:

1. Fireform by creating a false shoulder by necking up to a larger caliber and then necking down only enough to allow the round to chamber.

2. Back off at least 5% on your powder charge and work back up with the fireformed brass.

So I went back and measured every new, unfired piece of brass in the same lot. I found three pieces that were .020-.025” shorter than my fired cases when measured to the datum. My fired brass measures 2.043” to datum, and the normal, unfired brass measures 2.041” to datum. The three pieces in question measured ~2.018-2.023!

I’m guessing that I had a similarly short piece in the chamber when I experienced the case-head separation. So, poor QC on the Nosler brass I guess?

I’ll be measuring new brass going forward.