Simply call SA customer service, describe your issue, and see what they say.
I've had 2 M1A related issues where I used Springfield customer service.
1) Bought used M1A, gas cylinder lock REALLY loose, other couple small issues. Called customer service, mailed it in. had it back home, fixed, in 9 days. Of course no charge.
2) Picked up another used M1A. Trigger group was TIGHT in receiver. Other grigger groups fit fine. It was a commercial part. Called SA, shipped in back to them. ~1 week later, had an HRT trigger group in possession. No charge.
Note these were BOTH used guns that were completely covered by Springfield's customer service.
So before you get yourself MORE upset over a somewhat minor issue, do what you should have done when you first noticed it. Contact Springfield.
BTW, how does the rifle shoot? You have been shooting it, right?
I have my standard M1A in a USGI wood stock right now as my USGI synthetic is being painted. I think it has a similar gap as yours. I'll look at it tonight. The gun shoots like crazy in either stock, so I could care less.