Galazan advertises their leather hand guards to be made in a way that is safe for barrel bluing. Years ago I read something about the tannic acid on the leather is what affects the bluing if you leave it on the gun. I have used Galazan hand guard on a DHE for over 12 years (not shot a lot but left on the gun for prolonged periods) with no ill effects on the barrel finish.

Thanks for sharing that info ,