Well I did the .308" bullet test.
When I chambered these 2 rifles I made the camber to headspace on the shoulder instead of the rim. The Military chambers had the shoulders of the chambers .020" forward of the shoulder of the case and you can easily see the shoulder move forward on fired cases if you simply hold them alongside an unfired cartridge.
There is really nothing wrong with out the Brits did it but it does make case life a bit shorter if you don't neck size them after the 1st firing. Because I am supplying the dies and the load zeroed for the irons with the rifles I make, I took another approach.
I chambered the barrels so the cartridge will headspace on the shoulder with .002" clearance, and that moves the shoulder back .022". The down side is it also moves the case mouth/throat juncture back .022" so I have to trim my brass it 2.200 instead of the spec 2.222". However I found this is a cool way to dramatically increase brass life and still be able to size the case body a bit, so it enters the chamber effortlessly.

My other dilemma was the question: "What bullet should I use?"

Because these are fully custom rifles with iron sights set to 100, 200, 300 and 400 yards I need to file each sight blade to perfection, and that means I should have an accurate load capable of doing the job on any game that the rifle would be used against so the customer can duplicate that load for the life of the owner.

My 1st choice would be Woodleigh bonded bullets but they are very expensive and I do not trust the availability of them over time, because of the anti-gun politics of Australia and the looming danger of our own government shutting down importation of things "gun-related". So unless I could supply a lifetime's worth of bullets with the gun at the time of the sale (about 2000 bullets for a life time is a good guess, but there is no way I can afford to buy 2000 of them and hope someone will then buy the gun from me later.) I didn't want to zero with them and have an owner later not be able to duplicate that load.

As you all are probably aware I was asking for reports on bullet performance so I could make a decision about what bullet to load and zero with.

Problem solved!
I used .310" groove to groove barrels in this gun instead of .312. So I thought I should just try some 308" bullets and see if the metal flow from lands compressing the copper into the grooves would make a good gas seal and stay concentric. I was hoping for the best... but I knew there was no way to be sure other then to try it.

I loaded 40.3 Gr of IMR4064 with a 180 grain .308 Remington Core-Lokt in WW cases. It goes 2380 FPS. Here is how the first 3 shots printed at 100 yards.

OLYMPUS DIGITAL CAMERA by Steve Zihn, on Flickr

The group was as good as I can shoot with my old eyes, and also about 7" high.
So I lowered the rear sight (flied to the correct height) and made a windage correction. (went a bit too much) The next 3 shots are the ones in this groups making the triangle farthest to the left.

OLYMPUS DIGITAL CAMERA by Steve Zihn, on Flickr

So I went back just a little bit right, and fired the next 3, one of which hit the spot and 2 are so close I don't think I can correct for it at 100 with open sights. Those 3 are the smallest triangle you see, just slightly to the left, maybe about 1/2" to 5/8" from mean center of group to the center of the spot.

So I think I will go with .308s and zero the 200,300 and 400 yards blades with them.

I modified the dies to have a .307 expander instead of a .310" and it makes the cases hold the .308 bullets perfectly.
In the "180 grain 308" bullet world" there are LOTS of choices from very 'soft' bullets like Sierras BTs to tough deep penetrators like Nosler Partition and various bonded bullets, and I am sure all will be close to the right point of impact if the owners use 40.3GR of 4064.
I think my problem is behind me now.