516 Zero Change After Can Removal

[MarcSpaz]

I have a question about zeroing a 516 (or any other rifle) with a suppressor on it. I apologize for the newb questions, but this is my first suppressor.

This has me scratching my head. I am looking for some input before I spend a bunch of money on ammo chasing a ghost.

I have a gen1 516 with a 16" barrel. I have shot it without a can forever. I recently got a suppressor for my 300 Blackout and decided to try it out on the 515. Just so happens, at the exact same time, I put a new Burris 3-15x50 scope on it.

I performed the zero with the gas block in suppressed mode and the can on it. At 100 yards it was right on the money for 250 rounds. I had a mg left, pulled the can and put the gas block in normal mode. My group still stayed tight, but it moved up 10 minutes. I put the can back on it to see if the group moved back down and it didn't. At quick glance, I realized I didn't move the gas block back to the suppressed mode. At that point, I was out of ammo, so I packed up and came home.

So, is this normal behavior? If I plan on going back and forth between suppressed and not, should I zero the scope with no suppressor and the gas block in the normal position, and then dope the scope for the can and rifle in suppressed mode?

If I zero without the can, then add it, but not change the gas block position, will this impact the POI? Will it over-pressure the charging system?

Thanks in advance.

Spaz