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Posted: 11/30/2006 6:12:33 AM EDT
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I have noticed on several brands of uppers that I have, that the hole in the rear lug is actually slightly oval in the horizintal plane. What is the purpose / benefit of the oval shape rather than just your basic round hole? Not a big deal, just curious as to what functionial issue this addresses. |
The oval is intentional. It's there to compensate for minor dimensional differences between uppers and lowers. Think about it. If both the front and rear lugs were round, you'd need an absolutely perfect dimensional similarity between every upper and every lower, or alternatively, you'd have fitters sitting at the end of the production line hand fitting every upper/lower pair, and serial numbering the both pieces so they'd never get separated. The oval is a practical solution to what could be a major PITA. It's the reason I could order an upper today, sight unseen, and know it's going to fit the lower in my closet when it gets here. 
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I see where you are coming from shamayim, and that was my assumption from the start - to allow for variances between upper and lower. Just wonder why it is slightly oversized only in the horizontal plane. Would not a slightly oversized round and/or chamferred hole accomplish the same thing? Perhaps the oval shape does allow for some variance in fit without comprising the tightness of the vertical lockup at the rear of the receiver. I know I am picking nits on this, but the discovery of this feature aroused my curiosity. Friday afternoon, and time for a cold one - arclight out Nice to hear from a fellow Georgian, BTW |
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