Someone please explain: I took some dry erase marker today and colored the lugs on my M70 then worked the bolt a few times. when I looked at them, the lug beneath the claw extractor hardly had any ink removed and the other had a little near the bottom center of the lug.
What does this tell me?
Jeff
Posts: 2267 | Location: Maine | Registered: 03 May 2007
That you need to exert a little rearward pressure on the bolt. Unless you have something pressing back on the bolt while you work the lugs you won't be able to tell much. If you try pulling the bolt back into the lugs using the bolt handle then you still won't likely know what it say's because of the lateral slop in the bolt. You need uniform, direct pressure against the face of the bolt to tell you anything that you can use.
_______________________________________________________________________________ This is my rifle, there are many like it but this one is mine. My rifle is my best friend, it is my life.
Someone please explain: I took some dry erase marker today and colored the lugs on my M70 then worked the bolt a few times. when I looked at them, the lug beneath the claw extractor hardly had any ink removed and the other had a little near the bottom center of the lug.
What does this tell me?
Jeff
When heat treated many receiver designs bend upward on each end. As a result the locking lug on the bottom when closed bears and the one on top does not because the bolt is still straight.
Posts: 13978 | Location: http://www.tarawaontheweb.org/tarawa2.jpg | Registered: 03 December 2008
It doesn't have to be bent, most times it is an undersized bolt(.694 dia) being forced upward by the cocking piece-sear engagement on cocking ie. .703 rear reciever dia. This forces the lower lug to engage and pulls the top lug from contact- Even if everything is square and concentric! This is why benchresters BUSH their bolts and PTG sells so many replacement bolts. This may be why some people claim blueprinting doesn't work, the geometry is affected because of the SLOP in tolerances.
Posts: 90 | Location: NW PA | Registered: 20 January 2005
Try using a fired case in the chamber to hold the lugs against the receiver. Also take the firing pin assembly out of the bolt so you don't have the sear pushing the bolt up at the back. That may give you a better read.
Who cares about the rest. Start with a target, load development and then trouble shoot from there if the rifle does not meet your expectations (one MOA is better than most shooters will ever hold, BTW, in a hunting rifle from field conditions).
