OK, I was just as curious, and thought I would try to cut through this Gordian Knot. So, I called Kynoch. Sorry, but all this is gonna do is stir some more shit.

I asked David if he had ever pressure and velocity tested any vintage Kynoch .350 No. 2. He said yes and that pressure and velocity were very close to original published data. He also pointed out that the ammunition was old (Kynoch dropped it in the mid-50s). I pointed out that published data seemed to be scarce. He said he didn't think that it had been published since before WWI. He said standards were 2550 fps for 16 tons.

I told him of Bill's rifle and asked about the idea of firing both loads to see which it was regulated for. He said he has done same, but with the Rigby's found the throat too short to chamber original Kynoch 310 grain. He almost insisted that, since this rifle is specifically a Rigby double, it will be a .350 No. 2. I'm inclined to agree. I don't know how things are in Oz, but .400/.350 doubles are as uncommon as sympathy here. The No. 2s are much, much more common.

During our discussion, he also reiterated that the proof marks on British .350 No. 2 doubles are those of the .400/.350.
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