Bryan D,
I do not have a 223 WSSM but I have ran a couple through the wringer testing loads and I would say that for me personally, I feel the 22-6mm AI is vastly superior in every way you can imagine.
Its faster from the numbers I was getting with the 55 gr bullets, 4050 fps for the 223 WSSM vs. 4200 fps for the 22-6mmAI.
My 22-6mmAI was far more accurate with average groups in the .2"s compared to 3/4" for the 223 WSSM but to be fair I was using one of my custom Extreme Varminters in 22-6mm AI and a factory Winchester Coyote for the 223 WSSM.
For a repeater, the 22-6mm AI feeds much smoother then the extremely short and extremely fat WSSM.
Cases are much cheaper for the 22-6mm AI as well.
Only area I can think of where the WSSM has the advantage is that there is no need to fireform cases persay, even though any top accuracy nut will fireform cases anyway before doing any serious accuracy testing.
Now to the 22-250 AI. This round will offer the highest percentage of velocity increase of any of the AI rounds except perhaps the 250 Savage AI and the 257 Roberts AI. All three are on the top of the list for velocity gains over the parent cases.
The 22-250 AI will come extremely close to matching the WSSM in performance with much less fuss. I do not know of a brass maker that does not make 22-250 brass either.
If your looking to build a varmint rifle for high volume shooting I would recommend a standard caliber so there is no need for dramatic fireforming. That said I would still not use the 223 WSSM. I would get a 223 Rem or 22-250 instead.
For a high performance, limited volume varmint rifle I would either go with the 22-250 AI for its easy loading and Swift performance or the 22-6mm AI for its extreme performance.
Good Shooting!!
Kirby Allen(50)