Here in the UK we are only allowed to practice on military firing ranges and target clubs can usually get to use one only about once a month so I don't have the time to work up loads from scratch.
I have a Steyr Manlicher SSG with a 26" barrel in .308W. RWS factory loads jam the bolt so it is sensitive to high pressures. I would like to load 125grn Nosler Ballistic Tips or BlitzKings and also 150grn similar bullets.
I have done groups of just over 1" at 200 yrds with Norma 180grn factory loads.

I also have an FN Sauer in 270W that I would like to load 140grn BT bullets for. In the US the rifle might be called a Colt Sauer.

I have on order a Tikka Stainless Synthetic Varminter and would like to try both lightweight and heavier bullets in it. Ballistic tips again!

Do any of you have experience of loading for these rifles so that I have a starting point for to go from?

I have a variety of different brass for the .308 and .270 and can get Federal ammo in .223 locally. Will differing brass make a big difference to consistancy or should I go out and get a big batch of one brand of brass for each calibre?

I have a Nosler reloading manual from about 12 years back. Have things moved on much since then?

Lots of variables, I know, but I'm sure I am asking questions that a lot more would like answers to.

I'd get another manual just to get a second opinon on the mechanics. Try Richard Lee's. As for loads one of the load books contain all the loads from the different manuals for a single cartridge per book. If you know what you're doin' that's the way to go.
I hear Parliment has discovered you dirty reloaders are keepin' hundreds of primers and bullets sittin' around and not bein' regulated. Too bad.

Try www.handloads.com Good luck.

As for as reloading it has changed some but nothing drastic with your calibers. Its best to reload with the same manufactor brass,as brass will have a different voulume capacity from man.to man..Shot a lot of Tikkas and thay seem to shoot any bullet good.Try out your favorite load at first and see what happens. vangunsmith

Go to www.reloadersnest.com Good luck

You could probably make good use of the ladder method.
Load one cartridge with each powder charge from minimum to maximum load going in 1/4 gr. increments. fire them at the same aiming point at 200 yards and make a note as to where each shot hits. You will likely end up with a shring of shots on the paper with one or more clusters. Pick the tightest cluster, and use the load that that is the median load in the cluster. That load in theory will give you the most robustly accurate load out of the group.

I would do a further search on "ladder load development" to give a better explaination than I did.