Originally Posted by HauntedTank
Never ship mags filled ever it's a dangerous good and if not properly marked your fucked.
Be smart empty the mag for shipping and all is good.
This is why you bleed the mags a bit so they do not over pressurize when heated in shipping.
Keeping some gas in the mags at all times is a sure fire way to have it never leak. All the mags I have ordered recently from HK have had a small amount of gas in them - from the factory.