If it's that much off it will be very noticeable in my opinion. If you aren't sure then take it to a gunsmith or borrow the rods from a friend. I just eyeballed mine and they have been fine.

Depending on the situation if your barrel is from a quality manufacturer I don't think you need to worry. Also depending on the can make sure you check everything after the muzzle device has been installed. I heard of one guy that installed his MD with a crush washer and it caused a bit of a headache.