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Old 06-14-2009, 1:10 PM
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fredieusa fredieusa is offline
Join Date: Mar 2008
Location: Contra Costa County
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Issue discussed in this post is very uncommon. i have encountered this only once before. Both times it has occurred on domestic MILLED receivers. If it helps you to know, they were on different makes, this pretty much covers the domestic milled market (other than Arsenal)

Incorporating this to "fix" your company made name brand is also not advisable as it will most likely throw off your head-spacing. These details are only noted by careful and detail oriented builders, others simply overlook.

As shown in the picture, the bolt does not contact/meet the receiver at the charging handle side. Shown with a blue arrow.
The point of contact is on the point shown by the red arrow.
The area taken up on the point of contact (red Arrow) is very small. Usually it is on the other side (opposite).

It is common to see bolt making contact with the receiver/trunion on the charging handle side. This gives a wider area for the continuous impact over long time.

IDEALLY, we should have the bolt touching at BOTH locations, but that is RARE.

The gap is about 1.25mm ( .0495" roughly) wide. I have decided to decrease this gap by shaving off both, the receiver/trunion and the bolt carrier. Here the receiver/trunion has some material filed off (about 0.6mm) Circled on RED

Here I noticed that the bolt carrier is slightly convexed out, so I make that area smooth (circled in RED). This gave me the other .6mm or so needed.

As I tried the bolt carrier, it still did not want to make contact at the desired location. The carrier was making contact with the receiver at an undesired location and that too was smoothed out - Circled in BLUE.

With a little more nip tuck (filing and polishing) I have even contact on BOTH points on the receiver/trunion!
This will help dissipate the pressure created by the constant pounding of the bolt during cycling.

I use a marker to confirm even contact.


Last edited by fredieusa; 07-08-2009 at 1:12 AM..
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