How it was stored can and does have an impact on things. Ive shot pre WWII ammo with no problems, and had powder degradation issues/failures with surplus ammo from the 70's and 80's.
I inherited a bunch of reloaded 30-06 ammo my dad had that was loaded in the late 80's, early 90's, that was failing in the early 2000's when I started shooting it up. It had been stored, along with a number of pounds of powder in sealed cans, in a garage down by the beach, that wasnt temp controlled and was exposed to high heat and moisture in the summer and below freezing in the winter.
When I started to shoot it, I got a pretty much immediate warning something was up, when the neck of the round Id just fired in my M1, kept the next round from chambering, and came out around the bullet when that round was removed to see what was up. Pretty much every round in the lot, had the necks failing (cracks) and the bullets pushed through the necks with slight lateral pressure from your thumb.
On pulling the bullets, there was that telltale blue-green tarnish on the bases of the bullets, showing the powder had broken down and was degraded. I had to pull everything down, scrap the powder and brass and recovered and reused the bullets and primers.
When I checked the cans of unopened powder, it was obvious by the smell and the rust inside the cans, that that powder was going too.
I had a very similar experience with some 70's and 80's dated Maylaisiian 5.56 surplus Id bought in the late 90's. Ive also had some issues with other "surplus" ammo over the years too.You dont really see to much surplus anymore, so, unless youve been sitting on some of that for a couple of decades, its probably really not an issue. If you have been, Id be checking it to make sure.
I do think that the failures arent really the norm, and if youre storing the ammo in its original packaging in your house, youll likely be fine. Still, things can and do happen, and the only way to find out, is to shoot it, or at least pull a couple of bullets and look.
I buy factory ammo and I reload all the time. I also rotate both, by regularly, or semi regularly shooting both and replacing it with fresh as I do. The reloads get the bulk of the attention, and the factory is usually shot to replace the worn out reloaded brass as it wears out and time goes on, so the factory tends to be "older" than most of my reloads.
