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Posted: 3/2/2011 8:57:03 AM EDT
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I am gathering parts for a budget general purpose accuracy upper build for paper punching, long range plinking, and prairie dog/coyote hunting (I know, a bit of a oxymoron, but I am going to give it a try for the sake of tinkering)
I ran across a great article by Robert Whitley: http://bulletin.accurateshooter.com/tag/ar15/. My parts should be showing up today and tomorrow, and I will be working on assembly this weekend. I am using a slick side heavy wall DPMS upper, a DPMS DCM barrel, and vented free float tube. I know that I am not using the top of the line components that Whitley would use, but I found the article looking for build tips and tricks to maximize the accuracy of my build and will incorporate his suggestions to the extent practicable. I am sure that the link is repost on here, but I thought I would share anyway. In the article, the author says that front to rear play of the bolt should be kept at .003 to .005. I do not understand what he is referring to, and am hoping that someone among the considerable braintrust here can help sort me out. Can anyone explain what he means by that, and how one would measure/adjust the play? I am assuming it is one of those things like headspace that isn't really adjustable, but I am not sure. Thanks in advance for any help 
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Got this great explanation on another site:
"When correctly headspaced, the bolt face will be tight against the rear of the case or a GO headspace gauge and the bolt lugs will be tight against the lugs of the barrel extension. The front and back play is the space between the front of the bolt and the barrel face. The problem is any extra space allows the returning bolt to push the case deeper into the chamber and effectively resizing it too short." This would have to be set when installing the barrel extension, so unless you are building your own barrels from blanks, you take what you get I guess. I am not at that level, but I will probably measure anyway, just so I know. I will update when I do that on my upcoming build (this weekend if the stars align). |
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