If you have an engine that runs on diesel can you put gas in it?
The ratings are specific for a reason. There is a safety factor built in but you certainly don't want to rely on it. Suppressor companies have warranty departments full from people that made similar mistakes. It's nice that some of them are willing to take care of their customers but consider the added headache, wait time and possibility of another tax stamp.
Call the manufacturer and ask them what they think.