I loaded up a bunch of 223 /5.56 GFL ( Fiocchi) brass with 55 gr Hornady FMJ and 25gr of AA 2230 years ago. About 1500 rounds. I stored them in military ammo boxes for SHTF time.

My son dug into that stash and informed me that the case necks were all splitting. News to me as I tested these years ago.

Today I pulled 20 rounds, weighed the bullets and the powder and everything is correct. 55gr bullet 25gr 2230.

Did some more testing and this brass is f*cked, everything splits.

So, what kind of damage am I going to do to my chamber down the road when I need to shoot this SHTF ammo.?

Some brass is brittle and gets harder with age. If you shot a bunch of this its possible to flame cut areas in your chamber. Its not anything you did unless it was failure to anneal. And theres no real way to tell when or if you need to.

Sounds like stress corrosion cracking, aka "season cracking". Usual contributing factors are some degree of residual stress in the case necks combined with something in the storage environment which is attacking the brass along grain boundaries, usually ammonia. The ammonia may be from a range of sources including wood, cleaning solvents, decaying organic matter or mouse/rat urine. For long-term storage you could avoid this in the future by using cases whose necks were annealed and storing the ammunition in dry conditions free of any source of ammonia (sealed in air-tight cans with some dessicant, for example).

Split cases on firing will let hot gas impinge on the chamber. The odd one or two would probably not do much harm (I've never noticed it), but a steady diet of them would not do your rifle a lot of good.

Personally I'd be inclined to do one of two things: sort them and break down or dump all which are already split, and use the rest for practice before they get any older, or break the lot down, sort the brass and anneal the neck on any which are not split, then reload those cases (checking that they don't split when bullets are seated).

Honestly the best thing to do is sell them for .300 Blackout conversion.

With the proceeds start over.

Just my opinion.

Pull the bullets and chitcan the whole bunch. When in doubt, throw 'em out.

Older straightwalls I have, never fired police duty 38Sp. Remington UMC

A third of them of in a every box will split. Hate it too. Several hundred rounds worth. From the 1960s though. Meh

20 Years ago I had a small lot of Lapua brass in 7.62x39. Loaded 'em up and fired away. Had 10 rounds left over. 10 years ago shot those left over rounds. 9 out of 10 had necks split on firing.

In the event of a true SHTF scenario it won’t be of any consequence. If it wrecks your rifle, just pick your dead buddies rifle up off the ground and continue on.

Some brass here is well more than 50 years old - and it has not split under normal reloading and firing. Much of this has been neck sized only for a few reloads. However, along the lengthy reloading road I have experienced splitting brass - but it always has been from the same brand/lot and only after firing (not during storage) and discovered during the routine of inspecting every fired case before cleaning/reloading. I can't answer the question regarding potential "damage" as a result of firing those split cases - I think someone above gave a good reply - but I would not fire them wholesale unless in an unavoidable emergency situation with no good alternative - and with no other person near.

Sell them on GunBroker.

Thanks, I guess I wasn’t clear on some of the details.

I loaded these several years ago, packaged them in 50 round boxes
https://www.midwayusa.com/product/102046994
Placed these boxes in plastic ammo cans
https://www.midwayusa.com/product/1564294468

I also put two large desiccant packs in each ammo can.

These all look great, no corrosion, no discoloration, etc. they look as good today as the day I loaded them about 5-6 years ago.

They split upon firing .

Thanks

Try them in another gun. The chamber where they are splitting may be bigger than most. The brass has to stretch to split.

I've seen this happen when folks used a product that had ammonia in it to clean their brass.

Pull them down and anneal the brass. Load them back up. Brass , powder , and bullets are way too scarce to waste.

I believe that's the cause of some brass failures I've experienced, that and some batches should have been annealed before loading.

I don't stash a lot of reloaded rifle rounds, I change my mind too much on what I think the best recipe is right now and trading guns/barrels.

I had several hundred loaded .223 left over from my High Power days. I first noticed some splits in unfired rounds, later pulling these down I found lots of corrosion at the bullet case neck contact area. It even affected the powder in that area as well. A few of the primer pockets had the same corrosion, like what you see in range brass that's been left in the rain for a while.
All this stuff was loaded around 1999-2000. I did wash case lube off in 5-6 hundred batches with some kind of soap but I don't remember what type or brand, wonder if it had some ammonia as a ingredient? I also moved twice and no telling what was stored in close contact with the loaded rounds. I understand that just storing cases in the same room with a jug of ammonia can cause problems?

ETA Ammonia based copper cleaners?

You could count on at least 10 to 15 case splits per box on early '70's Remington 158 grain 38 Special round nose cartridges. Their .357's didn't fare too much better. I quit buying them.