AAC cans are high back pressure. You need to buy the various gas jet sizes and tune your rifle such that with round chambered, empty mag inserted you get:
- Suppressor on, suppressed gas setting. After firing: bolt locks back
- Suppressor off, suppressed gas setting. After firing: bolt does not lock back
- Suppressor off, unsuppressed gas setting. After firing: bolt locks back
This will dramatically change your suppressed SCAR shooting experience. I hated my SCAR16 suppressed until I swapped out the gas jet.
Midwest Gun Exchange and Parker Mountain Machine have the gas jets.
There is a good thread in the FN sub forum of TOS that discusses this.