What makes an AR accurate by Robert Whitley

[customcutter]

I found this article several years ago when I built my first AR a Grendel, and thought it might help some of the new members, and older members wring the last bit of accuracy out of their builds. One of the first things he talks about is upper receiver to barrel fit and bedding if needed. One thing we continually stress lapping the receiver. LOL

http://bulletin.accurateshooter.com/2015...s-answers/

[LRRPF52]

That list is just one set of parameters that I use when doing a build.

The other involves bolt work, barrel extension de-edging and polishing of the feed ramps, and other hand-fitting tricks. I think Whitley has covered them as well.

The one about the gas tube is usually overlooked by most people when doing a build, but is especially difficult on the RLGS. MLGS and CLGS are much more stiff, with less room for things to go wrong, but RLGS has less port pressure, so is nicer on the action and cyclic rate.

You can build an extremely accurate AR15 that will smoke most of the bolt guns on the range if you follow that regimen in the article.

[Mecharius]

Thank you for sharing this. Definitely a worthwhile read.

[Maddvaper]

Absolutely.Enjoyed the read ...now to apply.

[65Whelen]

Excellent read and guidelines when doing a build. I understand everything except #10 Front/Back Bolt Play. Can someone explain what this is and how to correct it if it's over .005?

[motoxxx_ryder]

Excellent read and guidelines when doing a build. I understand everything except #10 Front/Back Bolt Play. Can someone explain what this is and how to correct it if it's over .005?

if im not mistaken thats bolt lugs to locking lugs esentially. so you would put the bolt into the barrel extension twist to lock in place and measure free play there.

[customcutter]

Excellent read and guidelines when doing a build. I understand everything except #10 Front/Back Bolt Play. Can someone explain what this is and how to correct it if it's over .005?

I'm not a gunsmith or a machinist, but I think you would have to re-chamber the barrel in order to reduce the amount of play involved in the lockup between the bolt and e barrel extension. It can be done, but would involve, cutting the barrel back, re-chambering, and timing the gas port back to the 12 O'clock high position, just like sights on a rifle barrel. Probably not worth the expense.

[65Whelen]

Sorry guys this doesn't make sense. Wouldn't proper head space eliminate any excess play when locking up?

[customcutter]

There is a "tolerance" in head spacing. I don't have a set of "go" and "no-go" gauges, so I can't measure the difference for you. But the tighter your tolerance is to the "go" gauge, the less slop you have in your chamber. Most "accuracy" builders try for .002" or less. Then as soon as you start firing the gun the threads start "stretching" and seating in, so you get a little more.

Hope this helps, like I said I'm not a gunsmith, just my understanding of how it works.

Here is a quick video, and according to him there is .004" difference between go and no-go gauges.

https://www.youtube.com/watch?v=KICBv-0U87Y