I've used the same charge of both H4350 and Nobel No.O when loading for the 7mm-08. Results are identical, perhaps the Nobel powder having a slight edge on accuracy. On my comprehensive burn rate chart H4350 is the same as IMR4350.

Just for comparison the maximum loads with Nobel No.O and 100gr bullets listed in the 1975 Nobel Powder reloading book for the 243 Win and 244 Rem (similar case capacities as the .242 Express) are;

243 Win 42.0grs 3070fps
244 Rem 44.0grs 3080fps