Be very careful about how many you buy before trying them in the vintage guns. I ordered three flats of them several years ago on the same thought as you, that the lower pressures would be great in my vintage 12 ga. guns. I found that they misfire at an alarming rate in all my vintage guns except two, both hammer guns. I've tried them in several Foxes, L C Smiths....... even in a Browning BSS, and a MX8 Perazzi. Many, many misfires. I have deduced that the rim shape on the shell head allows them to sit a tiny bit deeper in the chambers than any other shell I've ever tried. This causes light primer strikes. The primer will be dented very slightly but will not ignite. My two hammerguns will fire them with 100% reliability, however. I have read reports that others have had this same issue with them, in a wide variety of guns.
They're great, soft-shooting loads that kill doves well, but are limited in what they can be used in. I would really like to find out that they have changed the rim/head dims so that this is no longer an issue.