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Old April 1, 2012, 09:22 PM   #1
Join Date: August 30, 2009
Location: Georgetown, CA
Posts: 29
Anyone interested in tighter-fitting AR takedown pins?

I am building an AR rifle with a BCM upper and Aero Precision lower. I bought a Spikes Tactical lower parts kit and decided to test fit the upper and lower before I built the lower. I notice a little slop in the fit between my upper and lower if I use the takedown pins in the kit. Nothing abnormal, like some cheapo rifles I've played with, but noticeable. I measured the diameters of these pins (the right way, with a micrometer) and they both measure .2482". The holes in my lower and upper are between .2505" and .2510" (measured with gage pins). I imagine the pins in most kits are intentionally made on the small side so that they will fit any rifle out there, no matter what. I'm a bit fussy about things that fit together, being a machinist for 34 years, but that's just the way my brain works. I haven't put the detents in the lower yet, so I substituted a pair of 1/4" steel dowel pins (.2502" dia.) for the takedown pins and the slop is GONE. They slide in and out like a dream. This is how I want my rifle to feel. I scoured the internet for someone who makes precision takedown pins of a slightly larger size and all I can find are removable ones with push buttons or huge heads, but neither manufacturer states the actual diameter of the pins. Also, I want to retain the detents so the pins stay with the rifle and neither of these pins do this. My intent is to manufacture some custom pins with the same design as the stock pins, but with a larger diameter, say .2490-.2498". I own a small machine shop, so this is do-able, but I'm wondering if this would be worth making several sets and offering them for sale, since it appears that no one else makes them. I would probably make them out of 17-4PH stainless steel that is pre-hardened to Rockwell C45 and bead-blast the exposed areas so they aren’t reflective. I have a couple of friends with ARs who would like a set, but I was curious if anyone else out there would be interested in something like this.
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