Lakota,
YES, working up published data is safe. I reload for my Mosin Nagant M44 and soon a MN 91/59 using Hornady and Hodgdon (on line) data. Start out with Winchester Metric 7.62x54R 180gr soft point (SP) and full metal jacket (FMJ) ammo. In my M44, with dark worn bore, the soft points grouped around 3" at 50yd while the FMJ scattered at 6"-8" at 50yd. By the time I shot up x100 rounds of Winchester factory ammo my reloading supplies arrived; special Collete (sp?) for my Forster case trimmer, RCBS dies, Lee shell holder for my auto prime, and a couple MTM 50 round ammo boxes. Since I already load for a couple 303 Enfields I had a supply of .311 Sierra and .312 Hornady bullets on hand, along with IMR 4350 and Hodgdon VARGET powder. So far my M44 shoots best with the Hornady .312 150gr SP bullets and 48gr of VARGET powder set off by a Winchester Large Rifle Primer (WLR), 2" at 50yd. .311 bullets scatter like the Winchester FMJs did, same powder and primer. But, if your reloading for the longer 91/30 rifle 4350 may be a little better since it is slower burning than VARGET. The down side is that a box of x100 bullets ($24.00) costs more than x100 rounds of surplus ammo ($22.00), not including the cost of your time, powder, and primer. I pick up my 91/59 Carbine, with excellent bore, Saturday and hope to take it to the range Sunday. I've loaded up x25 rounds using 48gr of VARGET with .311 Sierra 150gr SP and x25 rounds using 48gr of VARGET with .312 Hornady 150gr SP. At 2600fps these loads are close to the original military loading. If the bore on your rifle is worn, dark, tired, etc. .312 Hornady bullets weighing 150gr to 180gr, with IMR 4350 powder, will probably be your best bet to develop an accurate load early on.
Cheers,
George