I shoot 41.4g of H4350 and get 2600-2615 in my 18". I would have never tried the bullet, but a guy let me shoot his Black Hills 143s and they grouped very good in my rifle. I pretty much just replicated the BH load as close as I could.
Are you seeing any pressure signs at 42.6? And what velocity are you getting. I am shooting a 24” factory savage heavy varmit barrrel and at 41.7 getting just over 2800 with no pressure signs. When I graph my ladder test velocity over grains it shows a node at 40.3-40.7 at 26500 FPS then starts a pretty sharp spike at 41 grains. I’m still fairly new at loading and don’t like pushing the limits.
If you are truly getting 2800 with 41.7 I would leave it alone if accuracy is there.
Im getting no pressure signs in my 24" Kriger with 2774 fps and slight signs in my sons 24" cbi, cant remember his velocity.
41.7 is a very accurate load in most 6.5 creedmor rifles I have shot.
I'm doing in Prime brass: 41.6 out of my 24 in Proof research Barrel with the 147 ELDm's. Velocity is 2685, standard deviation 9, extreme spread 24. Half MOA all day long. Which is suitable for my purposes of having fun.
When I ran my ladder test I was using my Magnetospeed, so i figure the readings were accurate but 2,804 with 41.7 grains seems awful fast for a factory savage barrel. I was using Hornady once fired brass, annealed, with WLR primers. I was jumping .025. I missed quoted earlier I am running a 26" factory barrel. Thinking about Loading up a few more rounds and run it up to 42.5 or so and see if I can find a high node or start to see pressure. I figure I will end up loading at or around 40.5. I loaded 10 rounds at 40.5 and got a decent group under, just over a half inch but most of the group was horizontal. And it had an SD of 9. Best group I shot so far was Hornady Precision Hunter 143 it shot a 10 shot group, 100 yd, that I covered up completely with a dime. but the SD was mid 30s with a ES in high 70s or 80s but it was running about the same FPS as my 40.5 loads, 2650 avg