Last week I met with some local machinists to work out the best way to produce some new AR-15 handguards we’re workingon, and now I’m ready to go. I whipped out the final design:

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The magic of Solidworks, the program I use to design parts, is a feature called configurations (I think I went over this a few years ago concerning some other parts I made). You can design the basic part, and then use configurations to more or less automatically produce similar parts with different dimensions. Well, it’s not automatic, but it’s a lot simpler than designing a new part for every, say (as in my case), barrel length you need to support.

The parts above are for barrel lengths of (left to right) 10½, 14½, 16 and 20 inches. I use the configurations feature with a chart like this one to come up with the different parts:

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The green-tinted cells are fixed constants, basically the numbers I use to derive all the rest. I started with a design for a 16 inch barrel and worked out how many recoil grooves I need (the slots at the top of the part) as well as the length of the top of the rail. Because the recoil grooves are 0.394 inches center on center, all the rail lengths are increased or reduced from the 16 inch barrel length by multiples of 0.394 inches. That’s where the spreadsheet comes in handy.

Thought I’d be able to come in and get more work done seeing as it’s a national holiday, but the phone started ringing off the hook an hour ago and it’s driving me nuts (I’m not answering it, fuck it, it’s a holiday). Time to take a walk.