Originally Posted by Nimrodmar10
I think you answered your own question, change in ammo.
This!!! Anytime you change ammo you should expect a POI and/or grouping size change. And don't expect your rifle to shoot surplus ammo as well as tailer made ammo.
I can't tell from your post if you meant a POI change or your groups opened up. Doesn't really matter, as I stated above it can change both.
Also, you can expect a change of POI when shooting with a suppressor on and then taking it off. On our 3 M110's we get a POI change of 1 MOA when the cans are mounted, each one to a different spot. We shoot mostly with them on, so the optics are zero'ed as such. Just keep a log of the difference.