Not to make excuses, but manufacturing is tough ( I am in different industry, same material). Every vendor is TAXED right now, everyone is practicing lean manufacturing, anodizers are taxed, etc... I work in the buisness with a lot of aluminum, stainless steel, forging, etc. Things are not always as they seem- we have every Water-Jet, CNC, forgers, tumblers, etc... running full time. I work in sales, but I know these things because I have to. Many manufacturers are "building per order" instead of having huge amounts of stock sitting around.
I am a huge believer in EXPLAINING UP FRONT THAT there will be a wait. If it is going to take 6 weeks, tell the customer up front!! They will be more understanding & appreciate the truth. Glad you got your parts!!