Matt,
A view from Australia
Firstly calibre. The 300 Winchester will be much better for powder out here than the 300 Ultra. You can used 2209, 2213 and the new Winchester powder which is like Reloader 22. The 300 Ultra really is a 2217 caliber or Reloader 25. Don't know where you will get Re 25 from. The fellow in Canberra, I think it is Bruce Brown occassionally brings in Reloader powder. But if your 300 Ultra won't shoot 2217 you could have some difficulty.
Rem 700 is the easiest action to use because you can buy all the bits. Think V8 Commodore if you want to make a hot car or 350 Chev for a quick boat.
Sendero is a good place to start with a factory rifle, but
"start" is the key word.
For about the same money you buy a junk Rem 700 for the action, say $600, get a HSPrecision stock (I think Senderos now use the cheaper Bell and Carson stock) for about $700 and a chambered Tobler or Maddco barrel for about $600.
So about the same all up as the Sendero but you have an HSPrecision stock for sure and a match barrel.
The other way is the Model 70. In recent years Jewell triggers have been made for the Model 70 which really adds to the Model 70.
Basically, the Model 70 is nicer for a switch barrel rifle because of the intergral recoil lug.
On the other hand, if ever you go the "glue in" road the round Rem 700 is better (to get apart) and also the Rem 700 lets you remove the trigger without having to unglue the rifle.
As to the HSprecision rifle, it is very expensive and is essentially a nicely made Rem 700 with a Sako style extractor already fitted.
A lot of blokes on this forum may disagree with me, but in my opinion if you have a good barrel on a correctly bedded action and assume the scope/mounts and loads are right, that is about 99% of the accuracy potential you will get from that barrel.
In other words, a Rem 700 or Model 70 will deliver the accuracy as compared to custom actions. Lots of blokes out here have bench rifles on both Rem 700 and Stolles and can't tell the difference except that the Stolle is nicer to use.
Good luck with your purchase/project
Mike
[ 08-02-2002: Message edited by: Mike375 ]