Another head space and recoil lug question

[camcompco]

Ok, sorry for this less than exciting topic, but I just can't seem to find the answer anywhere.

Background: I have a full machine shop (metal working has been a hobby of mine for years). I have watched all of the key AGI videos, i have successfully blueprinted my action and have just received my first go no-go gauges. After reassembling my rem 700 (5R) i checked the headspace and find that the bolt closes very easily on the no go gauge. Before anyone asks I can say that i only had to take of a couple "thou" to get the action and bolt trued up, no biggy there, was pretty close to true as is. I have probably only fired 300 rounds through the rifle (bought new). I want to put a new thicker lug (already purchased) on it and that means pushing back the barrel (not sure of what the official name of the part that the existing lug sits on is called, but that is the area I am referring to). My question (finally right. . . .) is this, can i simply shorten the action side of the barrel a few thou at a time until my no-go gauge won't allow the bolt to close without reaming the barrel? I realize that there is a given depth between the outermost part of the barrel and the face that the bolt approaches, I can turn that down as well to keep that dimension as it is now. I was just hoping to not purchase a reamer if not needed and given that i need to shorten the headspace why would any reaming need to take place.

I hope I explained this question well, if not, maybe someone could point me to a place that labels all of the surfaces of a bolt and barrel so I can use appropriate labels in explaining things

thanks in advance all

John

 

[scudzuki]

If you faced a few thou off the receiver, it would decrease, not increase your headspace.
You make the headspace tighter by moving the chamber towards the bolt face.

Try this;
screw the barrel into the receiver without the recoil lug.
insert the go gage and close the bolt then screw the barrel in until it stops (zero headspace)
measure the gap between the barrel shoulder and receiver face with gage blocks or pins
measure the recoil lug you want to use
subtract the gap you measured between the barrel and receiver from the thickness of the recoil lug
this is how much you have to set back the shoulder on the barrel

I'd recommend you leave an extra two thou on the barrel shoulder as when you torque the barrel in you are going to lose a thou or so, plus another thou for headspace

the formula is
recoil lug thickness
minus
measured value of the gap between the barrel shoulder and receiver face with go gage against bolt face
minus
.002"

is far you will set back the shoulder (material removed).

At least that's how I did it.

Joe

 

[camcompco]

That is exactly what i was hoping to hear, thanks much !!. If i implied that i wanted to do anything with the action then it was just me going a poor job of "splain'n" things.

The action was "trued" on my lathe and that process took a couple thou off. The one question I have, I am not exactly sure what this part of the barrel is called, It is the part that is near the barrel hole that the bullet would first clear that the bolt face would be close to touching when the bolt is closed. . .just don't know the name of the flat part. My question, i assume that i have to turn down that "face" as much as I turn down the outer shoulder to keep the lip between this "face" and the outer shoulder a constant (it's currently 0.700")

is that right?

thanks again guys