I don't know about a relief cut, but I used to mill or grind 2 flats on the barrel at the chamber so I could get a better grip on it. I don't know what kind of receiver wrench you are using, but I usually use a 2 piece split-block type that goes around the outside of the receiver. Whichever part you are trying to move will require a large hammer on the wrench handle to break it loose. These guns have a bad reputation when it comes to barrel removal and it is well deserved.
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