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FYI, the ATP regs require engravinig (they actually specify a min depth). If you are doing this for a SBR then you will want to engrave.
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Laser company mentioned earlier is plenty capable of doing so. Many lasers of the high dollar variety are more than capable of engraving into metals like aluminum and steel. Min depth is .003, to put that in perspective, if you have a suppressor that is user serviceable the baffles are probably .005 smaller OD than the ID of your suppressor tube.
MARKING REQUIREMENTS – NFA
FIREARMS (27 CFR § 479.102)
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For firearms manufactured, imported, or made on and after January 30, 2002, the engraving, casting, or stamping (impressing) of this information must be to a minimum depth of .003 inch.
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