Snuffy
While it is true that no two rifles are exactly alike and different lots of powder, primers, bullets etc. will vary somewhat, your statement, "Using somebody else's load as a guide line is no better than looking a load up in a loading manual", is not realy true. If a load load works very well in in my Savage Model 12 BVSS with 1/9 twist rate there is a pretty good chance that it will work well for you in your model 12 Savage as well. You will probably have to fine tune the load by varying OAl and powder charge, this is due to in part to harmonics and in part to chamber length which can vary slightly due to a couple of factors, to your particular rifle but it most likely will be a very good starting point. I know this for a fact because I have several duplicate rifles and what works well in one will work well in the other. I have also recomended my loads to other shooters with the same rifle and it has worked well for them. By the same token, if you you go to any big competition where a lot of competitors are shooting similar rifles in the same calibers with barrels that have the same twist rate you will most certainly find that there are several competitors using almost identical loads.
Generally speaking, just because a load makes it into a particular loading manual does not mean that it will shoot well in anyones particular rifle. What it does mean is that particular load, using specific components, will be safe to shoot in just about anyones rifle/pistol. Once you start considering things like rate of twist, length of barrel and barrel/firearm manufacturer you can start to weed out loads that don't work well in a particular type of firearm and hone in on the loads that will work well. I am willing to bet, although not much as I am kinda broke right now
, that the OP, if he gets enough responses will find a lot of people will recomend the same or almost the same load for a particular firearm. You will also see 3 or 4 powders recomended more often than anything else and you will find the same when it comes to bullets. I have had great success loading 26.5 grains of H-335 or BLC-2 with either the Sierra 52 grain BTHP match or thier 53 grain HP match. I can consistantly get sub 1/2" 5 shot groups using any combination of the above and usually better. This data is for my Savage 223 BVSS with a in 14 twist barrel. This rifle also does just about as well with the same amount of either with a 55 grain Blitz King bullet. Recently I have started doing a lot of experimenting with Ramshot TAC, cause I bought 23 pounds of it from Midway at $9.99/lb.
, It also shoots very well with all of these bullets with loads in the 25.5 to 26 grain range. Some of these same loads have given pretty good performances in my ARs as well.