Old Ammo Affecting Rifle Accuracy?

Please excuse the ignorance of this question but it is possible that using old Ammo can affect the accuracy of your Rifle?

I've have quite a few boxes of at least 30-year Winchester 308 Ammo, and for cost reasons usually use it. However, I recently tried some new Winchester 308 Ammo (same Bullet Head, Grain etc. as the old stuff) and the new stuff shot a way closer group with my most 'finicky' rifle (a Rem Model 7, with its thin barrel and all).

So, can old Ammo through simple deterioration over time in fact affect accuracy?

I'm not a hand loader, so don't fully understand gunpowder theories etc.

Thanks

yes and no.....
it can deteriate but lots of milserp ammunition going bang that is way more than 50 years old without issue.
how bad/inconsistant is the 30year old stuff??? most probably not bad enough to cause miss or issues under 250 yards I would guess
also ammunition has improved somewhat over time....go back not much more than 30 years and MOST reloaded stuff was better than factory as was more consistant.

Mickey duck is right how bad -- I use some real old ammo in my .308 -- deer dont worry - in fact they just fall over

Model 7's are renowned for being finicky. If it shoots said ammo in to 1.5moa, maybe a tad bigger, then alls good. If its greater than, then maybe its not quite so good.

There is no question that projectile manufacture quality has improved dramatically in the last 30 years so your results don't surprise me. I had the same rifle improve from groups of about 40mm 30 years ago to about 20mm recently with nothing else changed.

Thanks all. That's helpful.

I have some old stuff that still shoots as well as it used to, but I am a bit fussy about storage. Large changes in temperature and/or lots of movement (like being stored in a glovebox of a ute that clocks up high milage on gravel roads with a rough running motor) will accelerate deterioration.

Also as per what Husky says, with the model 7 it is probably more to do with the modern ammo being of a flavour that your rifle likes than it is to do with comparative age.

If you shoot the two different loads through a more stable platform, the expectation would be that there will be much less discrepency.

Possibly the case necks cold-welding/fusing to the projectile over time, some being more effected by it than others causing a neck tension difference. Not some I'd ever worry about, but I've heard of target shooters seating their projectiles most of the way in at home, and completely seating them at the range so they get to fire them seconds after seating to the required depth. These are the sorts of target shooters who weigh their primers etc.