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Posted: 3/31/2005 8:46:10 PM EDT
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I am new here and I have only assembled three AR's. However I am planning to change my A2 to a flat top receiver and I came across a Cardinal Forge flat top advertised as having the small pivot pin hole. Now, I have not had any pivot pin issues on the three AR's I have built and so I am curious as to the dimensions of large and small pivot pins/holes. I don't want to buy an upper over the internet and end up with one that won't mount on the Bushmaster lower that is currently part of that rifle. Anyway you all seem to have so much combined knowledge that I thought I would ask the question and see what i come up with. Oh BTW, the Bushmaster pivot pin calipered at .247 so I guess that is a .250 hole in the upper. (probably like all Bushmaster lowers I imagine) Anyway any help on the dimesions would be appreciated. |
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The only Uppers / Lowers made with different sized Pivot Pins are the Colts. The earlier Colts were made with the "Large Size Pivot Pin (.315" Diameter). The newer Colts are all now "Small Size Pivot Pin" (.250" Diameter). I seem to recall that one Manufacturer made a "Run" of "Large Size Pivot Pin (.315" Diameter) Upper Receivers for the Colt Lowers in the "After Market", but that was years ago. NOTE: "Small Size Pivot Pin" (.250" Diameter). is Mill Spec & the "Norm" that you will see. |
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