This is in regard to changing the front sight base and muzzle attachment:
Anything related to the front sight base, the muzzle attachment, and to the end of the barrel/muzzle will sustain a voided warranty. If a problem occurs to another part of the rifle, then the warranty will remain in effect.
Be careful who you choose for a gunsmith to peform your modifications. I've had a few customers have these modifications go wrong on their rifles.
Dan