I didn't plan to, however I now have thousands of firearm fastners, nuts, t-nuts, roll pins / split pins, washers in all the gunsmith gauge diameters, etc. Nothing as aggravating as working on a project and not having the correct hardware to assemble the parts professionally.
I would recommend McMaster Carr for virtually all of your fastener needs; you can get 25-100 pieces (a non-commercial life times worth) of whatever for what usually you pay for 3-5 pieces elsewhere. I have purchased all the gun screw kits from Brownells, their blank screw set (i.e. thread your own). Other sources are Pachmayr , Forster, Marshalls Hardware, Hillman etc.
Finally, divorce yourself from any idea of using hex head fastners for firearm applications, whenever possible; use torx / torx-plus, your life will be better for it.
Speaking of Hillman, they have a nice gunsmith thread screw checker (for a few bucks ) that compliments the usual screw checkers that are pretty handy to have on the bench.
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