This is the 5th video in his six part series. If you are building from a flat, then you need to pay careful attention to this. He shows how to file the ejector tip down plus also shows how to do the spot heat treating in this video with a MAPP torch. I spot heat threat the fire control group (FCG) pin holes but I heat treat the entire lower rails outside of the receiver before I spot weld them in. His method works just fine so pay attention. If you are building from a finished receiver then the odds are it has already been heat treated – if you have any doubt, ask the vendor that made it.
By the way, if you need a MAPP torch, go to Home Depot or Lowes (I prefer HD) and buy a Bernzomatic MAPP torch. Personally, I use a MECO Midget Oxy Acetylene (OA) torch that works great for sheet metal. Do some comparison shopping though. It may be real expensive online if they ship the gas too.
Note, the Bernzomatic MAPP torch is definitely more portable so there are times I use it but if I need a lot of heat fast, I get out one of my OA rigs.
Here are the links to each segment – when you click on them they will open in a new tab:
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