Does ammuniton really expire

[Kayback]

I would use it, but not for the intended purpose, for that it makes no sense.

Because current loads don't replicate 15y/o ammo?

[AK-Gunner]

If you are really going to zero your scope, you'll have to buy all your ammo from the same batch. 15 year old ammo won't replicate anything else but itself.

[Messor]

Because current loads don't replicate 15y/o ammo?

I think the OP doesn't mean sight his scope in, I suspect he means get his scope on paper after bore-sighting, then fine tune with the hunting ammo of choice.
So it's not a case of sight in with this and hunt with that.

Regarding your question, I bet it damn well replicate today's ammo, probably made in the same machine as well.
I know a 270, and I know the load he is speaking off.
It's loaded very mildly, no way it's near a compressed charge so no clumping of powder I can foresee.
If it didn't get wet I bet it's just as good as the day it was bought.

However, it's been mentioned that the alloy used in the mantle of pmp bullets differs to those of most others.
Some people are experiencing "issues" because the copper fouling profile differs, and if you first shoot the pmp and then your other ammo the desired results "might" not be acquired. So now you have to zero your scope, then first clean your rifle, then zero with hunting ammo.

I would use the ammo as practice and be done with it. Afterwards clean and zero the rifle with the normal ammo.

[Kayback]

Ah thanks