I would start at 23.0g and go up one shot for every .5g loaded...
using a thick primer cup like a 7 1/2 or cci450(br-4).
For instance, load one shot and one shot only looking for pressure signs......
etc until you determine what is a max load for your gun, accuracy will be within 2.0g of max.
You should get some screaming velocities out of 4198 with the 40's.
In my .223AI, which is a 1:12 twist, the accuracy load with 40's is 24.4 grains of IMR4198. I use IMI brass, Rem. 7 1/2 primers, and that load is right at 3,900fps. Max is 4050, but i don't get the accuracy at that velocity.
I spend Sunday working on my 223AI. I discovered that mine likes H335 with 50 grain bullets. However, it does NOT like H335 with 40 grain bullets. H322 seemed to work much better with the 40 grain Vmax.
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