Printing barcodes to receipt printer

I'm running out of BOCA ticket stock and instead of replacing it, I am looking to print barcodes to the receipt printer. I am pretty sure this is possible but my first attempt yielded quite unexpected results: the template uploaded and printed fine, but none of the fields merged as they usually would--I laughed when I saw a piece of receipt paper come out with "%BARCODE" across it. There must be a step I missed to have the fields fail to merge. Any tips or pointers? Thanks! 
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