should this be "dressed'?

[copterdrvr]

Here's a picture of the bolt face of my JP "matched" bolt that is in my LR 308 build that is based on a JP 20 inch barrel and low mass bolt carrier. The rifle now has approximately 200-300 rounds down the tube.

It appears that only two "ears" of the bolt are making any real contact with the face of the barrel assembly. My question is should I dress these two high spots to allow the entire bolt face to be squared up and make a more squared up contact with the barrel face?

I'm not sure how this would effect a semiauto but I'm assuming it would be the equivalent of truing up the action of a bolt gun-am I close or is this a non-factor in a semi?

 

[wareagle700]

Looks like that wear is coming from stripping rounds from the mag rather than touching the back of the barrel. If it is wear from the barrel, you have a problem. Bolt lugs wear on the back side, not the front.

 

[copterdrvr]

Excellent info and makes perfect sense-thanks. I was under the impression that the majority of the contact was on the back side of the bolt ears but I've seen more than a few AR bolt faces that looked pretty shiny-does that indicate a problem with headspacing?

How much clearance is usually between the bolt face and the barrel face when headspacing is correct?

 

[wareagle700]

How much clearance is usually between the bolt face and the barrel face when headspacing is correct?

It can vary and I have never threaded a barrel for a AR barrel extension, so I don't have the best answer for you. However, with a bolt gun I believe .002"-.004" of clearance is recommended. The bolt lugs should not touch the back of the barrel when chambering or firing a cartridge. Some of that wear you see may be from people dropping bolts on empty chambers.

 

[copterdrvr]

Again, excellent info-thanks. Your technical knowledge is obvious so I have another question-why would dropping a bolt on an empty chamber allow it to contact the barrel face-I first thought it would be stopped by the cam pin but then it dawned on me that the bolt is being pushed forward by the tube spring and the bolt itself will determine how far forward it all travels-right?

Come to think of it, the "depth" of the back side of the slot cut for the cam pin would have an impact on how far forward the bolt itself would move-would it not?

 

[wareagle700]

I'll take a shot at this, someone may be able to elaborate.

When the bolt moves forward, chambering the round, the round seating in the chamber stops the bolt which causes the cam pin to and bolt to rotate closed because of the mass of the carrier moving forward. On an empty chamber, there is nothing to stop the bolt moving forward except the back of the barrel. That's what cams the bolt into battery.

 

[lennyo3034]

I'll take a shot at this, someone may be able to elaborate.

When the bolt moves forward, chambering the round, the round seating in the chamber stops the bolt which causes the cam pin to and bolt to rotate closed because of the mass of the carrier moving forward. On an empty chamber, there is nothing to stop the bolt moving forward except the back of the barrel. That's what cams the bolt into battery.

I think he's right. It difficult to tell on an AR, but Garands or M1as if you close the bolt on an empty chamber, the bolt will still wiggle a bit.

 

[copterdrvr]

Awesome-thanks for the info guys!

 

[trevoro]

How does it shoot?