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Posted: 1/11/2003 5:07:00 PM EDT
| I don't know the difference but I see posts for small pin/large pin.. What exactly are they referring to and how do I know what mine is? I have a Post ban Bushmaster...Any replies would be appreciated for my lack of knowledge on this subject. |
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There are two types of small/large pins - fire control pins and pivot pins. Colt semi-auto production from 1963 to sometime in the 1990's had big pivot pins. Military guns and just about everyone else's lowers use .250 pivot pins, while Colt used .315 pivot pins on most until the mid 90's. Military guns use .156 (small) fire control pins, as did everyone else's guns until the early 90's. At that time, Colt started using large fire control pins (about .170) for the hammer and trigger, to further discourage conversion of their rifles to full auto, or use of their rifles as full auto host guns. Military rifles and all production but Colt early 90's on have always used .156 fire control pins, and .250 pivot pins. Current Colt production uses .250 pivot pins and .170 fire control pins. There are some transition guns with both .315 pivot pins and .170 fire control (worst of both worlds). |
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The pin size difference they are referencing is the forward take-down pin. I believe Colt was the only manufacturer to produce anything other than the small pin version. This was a self-imposed effort by Colt to limit the ability to mate a civilian lower to a military upper. Your Bushy should be the 'standard' small pin receiver. There is a more detailed explanation of the differences on the below link. http://www.biggerhammer.net/ar15/uppers/ |
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The terms are [i]standard[/i] pins and [i]non-standard[/i] pins. Pins larger than standard are --- wait for it [;)] -- non-standard. Only Colt's produced lower receivers with non-standard pin holes. Several makers of uppers have produced then with non-standard holes to mate to non-standard Colt's lowers. Not only did Colt's produce lower receivers with non-standard pivot pins, but they produced many with non-standard fire control pin holes. -- Chuck |
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