I recently purchased a Rumbler that had the Blaze Away blessing (I bought it for the Adhesive Charge blessing it also had and its better stats).
The Rumbler has a single round. It cannot “keep shooting” because once you have fired, that’s it. In the off chance that reloading did not affect the blessing, I tried it out in the testing grounds, but there was no icon indication that it was giving me extra power.
So unless I’m missing something, there is absolutely no reason why this blessing should spawn on this weapon.
(I’ll still keep it for when weapon crafting comes online and I can transfer it; it could pair well with a heavy stubber!)