Home Forums Hunting & Shooting Hunting Rifles Short Throat Cooper: Update and Results

The other thread has deteriorated (shocking), so a new thread seems appropriate.
I started with an 87 Vmax seated to 2.715 COAL that would not chamber in the Cooper 243AI, trying to determine how short the throat is.
Here is that 87 VMax at 2.715 in the Cooper magazine, room to run:



I proceeded to bump the bullet by .005 at a time, stopping to check for a COAL that would chamber.

At 2.655 OAL, the bolt finally closed, .06 deeper than my starting OAL.

I took the sharpie and began searching for the magic little squares. 2.645 seemed to do things nicely:



I kept going down in .005 increments just to see how other depths looked. From top to bottom you are looking at 2.640, 2.635 and 2.630:



From what I could tell, things were getting pretty square in the 2.630 range as well. Of course, plenty of room in the magazine. No worries there: