Originally Posted By Jdurzua:
I didn't disregard him! There has to be a reason why now after thousands of rounds and multiply cleanings from tube to barrel, that this has started to happen. I don't believe that the moons happen to align right to make this happen. I did add a quarter to the tube and it is now working fine. So now I must figure out now what is out of spec. I did compare the buffer to a new one and they look identical down to the height. If I am to shave the extension tube how the hell do you do it to keep the rim to hold down the pin still and still get enough to change anything.
Receiver extension thread size is 1 3/16"- 16 pitch., So, 16 threads to the inch, which each thread being .0625" wide.
So it comes down to working in .0625 increments to shorten/face the tube on a mill to maintain the same index of both the butt stock index and the front of the tube to the retaining pin for retention at it is now.
You stated the the bolt face is now flush with the back of the ejection port, and we want to have it 1/4" forward of the back of the ejection port by shorting the tube, so 1/4" coverts to .250", and since that number is dividable by .0625 cleanly (4 X .0625=250), it comes down to shorting the tube 4 winds or .250". If the face of the bolt is slightly behind the face of the bolt, the we can take off another wind./0625 off, with the new trim length being .3125" instead.
And again, we are looking for the face of the bolt to stop between 1/4" (.250") and 3/8" (.375"). and just need to work in the .0625 lengths to maintain the same index of the tube now to the butt stock and buffer retainer index at is currently is.
To add, if you want to move the end of the tube closer to the center pin of the buffer retainer, subtract that amount from the trim number.
So here, lets say that the the end of the tube is .065" from kissing the center pin of the retainer, and we are going to face the end of the tube .250" back, the new set back length would be .1875".
So that answers the how much, and the how to shorten part, either mill to set back the tube the needed amount, or just wrap a layer of masking tape around the front of the tube, use a set of calipers to measure back to scribe in a line, then break out the hand tools to set the face back the needed amount (back to the marked line).