You really don't need a fancy rest to boresight and zero a rifle. Honestly, sandbags work very well - to the point where I don't take my mechanical rest to the range any more, and just keep it for working on guns. Here is a great article on the subject with input from several masters - https://www.qdma.com/how-to-bore-sight-most-any-type-of-deer-rifle/
You really don't need a fancy rest to boresight and zero a rifle. Honestly, sandbags work very well - to the point where I don't take my mechanical rest to the range any more, and just keep it for working on guns. Here is a great article on the subject with input from several masters - https://www.qdma.com/how-to-bore-sight-most-any-type-of-deer-rifle/