I have a mil-spec from Springfield that functions flawlessly but after a round is chambered a couple of times; the bullet is noticeably seated back into the case.

I rotate the first couple of rounds but it doesn’t take too long for defensive ammo that isn’t fired very often to set back into the case.

The obvious answer is to shoot that ammo more often, but money is tight right now.

These are Gold Dots and I have polished the feed ramp.

Liability gives you general answers.

When I notice any of my ammo having a noticeably shorter OAL than it is supposed to have, it does not get fired in my handguns. Period. I assume pressure goes up exponentially and choose to err on the side of caution, as I have become too fond of my hands & eyes.

Sorry I couldnt give you a better answer, but I reload some, and dont want any problems from my stuff.

How much is it changing?  Does other ammo do this too?  How often do you clean your .45?  Does it affect accuracy?  I wouldn't be concerned with chamber pressure here, but more with functionality and accuracy.  Functionality associated with jamming or not reaching full lock up and accuracy with some bullets being on the rifling and others off the rifling (less of a factor in a pistol); consistency is key. Bullet length varies considerably with bullet type.  The main factors between bullets that affect chamber pressure are bullet weight and the friction coefficient between the bullet and the rifling.  Typically with the .45 acp you have quite a range of safe functional OAL.  I have a couple of Springfields and have never noticed this happening; I will check a couple of different types of ammo though.  Typically my re-loads are short as it aids in feeding (lead) in my G-21, of which I have fired about 4K rounds of lead SWC and LRN though with excellent accuracy out to 50 yds.  (Just to put the lid back on the can of “don’t shoot lead in your Glock” worms.)  Let me know what you find on the changes in OAL and we can compare that to anything I may find.  

Maybe swapping barrels/mags from your other SAs (you said you have) may point you in the right direction?
Using a bullet puller to get the OAL back or using a GI hardball as the "first" round until you figure it out?
That did not answer your question, Attman, but maybe gives you other avenues to try out.
Glad seeing you here too, CavVet.

Only the Gold Dots get chambered and not fired, that’s rare for FMJ in my case.
I’m talking about 1/8” shorter than a new round. (I’m guessing here, I don’t have any way to measure it).

I could hand you this round in front of me and a new round and you would see the difference right away.  It’s been chambered maybe 3-4 times.

The thing is – the gun has never failed.  Not once!   I don’t want to play with it too much.
It’s always clean, trust me.  I don’t have another .45.

If one of you guys could load a gold dot 4-5 times and tell me what happens in your pistol I’d really appreciate it.