I've worked a lot with this powder, and Ganderite's advice is sound. A powder's "Burn Rate" is not fixed - it varies somewhat with the application, and that's why "Powder Burn Rate Tables" vary.
It's probably from my website where you got the notion that its Burn Rate is close to IMR4320. In all of the cartridges in which I've used it, the pulled 8X63 powder has been slower than H4895 and faster than H4350, often close to IMR4320. That's a pretty wide range (about 10 grs in many cartridges with loads for those two powders), and the 8X63 powder will fit somewhere between the two in all of the cartridges in which I've tried it.
Here's a good method to establish a safe load with pulled 8X63 powder. If you don't have a chronograph, buy one or read no further. You shouldn't be developing loads, especially with "unknown" powders without one:
- with the chosen cartridge-bullet combo, do up 3-4 mid-range loads with each of H4895 and H4350, e.g. with the 30-06 and a 180 gr bullet, try 42, 43, 44 and 45 grs of H4895 and 52, 53, 54 and 55 grs of H4350. Record the Muzzle Velocities (MV's);
- with pulled 8X63, do up 5-6 loads with the same cartridge-bullet combo, starting at the H4895 load, in this case 42, 43, 44, 45, 46 and 47 grs. Record the MV's; and
- STOP, when the pulled 8X63 load exhibits a MV equal to the top H4895 load.
This will be a conservative load pressure-wise, and you could go a bit faster, and if you do, the H4350 loads are your sanity check. If you are equalling the MV's of any of the H4350 loads, you are doing that at a pressure higher than the H4350, and if you equal the mid-range H4350 load's MV's, you have probably gone too far and should back off a bit.
