CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.
Wendy,
I ran the Hornady 154 grain SP listed in Hodgdon's IMR 4350 load in both Gordon's Reloading Tool and QuickLOAD and then substituted the 156-grain Oryx into it, using the 2.800" COL Hodgdon listed. In both programs, the pressure and velocity actually went down slightly with the Oryx. This is because, despite its slightly greater weight, it is about 70 thousandths shorter, so it took up less powder space in the case. If you stick with that COL, you should be able to use loads intended for the Hornady 154-grain bullets.
I will point out that both programs thought Hodgdon's top load of 47-grains of IMR-4350, compressed, would produce excessive pressure with both the 154 Hornady and the 156 Oryx. The software is not as accurate as actual testing, of course, but it usually produces lower rather than higher-than-measured pressure, so I take this as a caution. Hornady's top load is just 45 grains for 2700 fps, so you might be more comfortable stopping there.
For Reloader 15 and 17, the software thinks you can increase the Alliant 160-grain Speer bullet maximum loads by half a grain for the Oryx and that will be in the ballpark of matching peak pressure, again with 2.800" COL.
Both Hodgdon and Alliant used Remington cases. Hodgdon used a Remington 9½ primer, while Alliant used a CCI 200 for Reloader 15 and a Federal 210 for Reloader 17. As always, work up from 10% below the maximum of your choice.