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Old 05-23-2019, 08:58 PM
DittoHead DittoHead is offline
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Join Date: Sep 2006
Location: Central Virginia, U.S.A.
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Originally Posted by rick w. View Post
I got a return email from Cooper very promptly, refreshing in these times of customer interface for me.

I was told what the 17MachIV neck diameter should be.
You can't leave us hanging after all this!

What's the diameter?

Originally Posted by rick w. View Post
There was a short discussion on the ejector as well; possibles for specific environment requirements, food for thought.
What does this part mean?
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Old 05-23-2019, 11:00 PM
GrocMax GrocMax is offline
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Location: McKinney TX
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There is a possibility the scratch happens during extraction as the case shoulder passes the sharp edge of the corner of the bolt raceway in the receiver.
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Old 05-24-2019, 07:12 PM
qwk qwk is offline
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Join Date: Aug 2017
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The early Cooper Mach IV's serials start with a G. The later ones(1998+) are the VGxxx. Sometime around 2000 Cooper had those accuracy problems, along with some bad reamer(s). The neck on those was 201.5 I believe.

I have an early one circa 1994 with a 200.5 neck.
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Old 05-26-2019, 01:04 AM
rick w. rick w. is offline
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Join Date: Sep 2006
Posts: 842

A Cooper representative informed me that a 21 (told him the serial prefix) was 0.2015". I am sure that is with an unmodified barrel of course. Looks like that to me so far, but proof is in the pudding like most things; really cannot assume things other than as general guidance; I know the buck really stops with me alone.

Sorry to be a bit late, but having to sleep some now; cannot always do what I want; sorta speak.

The rep told me about the heavy spring in the ejector as well, and not to go over 1 or so coils without loss of function. Benchresters usually replaced, clipped, or removed the ejector springs for their sport, guess I spent some time there in my earlier days; used to that method.

I bought a new K&M neck turner, turning mandrel, and holder for this rifle, hope to get the barrel pulled and get on with it.....get the visibility....... Most of my rifle stuff does not have 1" at the action, so new bushing is needed to be made up as well as the action wrench bushings, but all in due time; just have to plan a little.

I think the MachIV is a piece of rifle history, like others we all shoot and enjoy, looking forward to it
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