With the 48th edition, Lyman is using a SAAMI pressure barrel. For the 150 gn Sierra SBT they start with 39.0 gn of 4895 for 2265 fps from 24" and end with 43.5 gn at 2609 fps.

IMR's brown book (much older data) has a "Speer 150 gn Spitzer" over a max of 36.0 gn of 4895 for 2435 fps from a 25.5" barrel.

Both used 3.00" COL.

With such a discrepancy in load data, one will want to start at the lower end. The Powley Computer reckons the Lyman data is typical in the general sense, but don't bank on this.

I'd start at 35 and watch the chronograph. Using the Powley computer to extrapolate Lyman's 24" barrel data to 30", you should be around 2340 with their starting loads and 2700 with the full loads. With my 30" rolling block, I wouldn't go beyond 2400 fps. For what it's worth, Lyman's starting load for 4895 for the 180 gn spitzer was nearly spot on for me, after using the Powley to correct for barrel length.