Gary,
1/2 minute accuracy is a term easily used and not easily obtained - particularly from factory rifles that are given real-world tests.
We can all get the odd exceptional group but the real test of how accurate a rifle is requires averaging many groups and particularly keeping track of whether the first shot is in the group formed by subsequent shots. The number of shots constituting a test group must also be determined - 3-shots or 5-shots.
I believe that some Senderos - or Laredos or whatever might shoot into your accuracy objective but not many - particularly out of the box with factory ammo. You might get the odd exceptional three-shot group but many new rifles will not do one inch, factory or handloads.
Current rifles are notorious for leaving the factory with the absolute bare minimum of handwork and adjusting, so the result is difficult triggers, sloppy bedding and so-so accuracy.
I have shot Laredos, Stealths and a variety of Rem. heavy barreled models and usually find a wide variance in out of the box accuracy. 1/2 minute accuracy with the larger calibers is NOT common, even for three-shot groups.
Rebedding, adjusting triggers and careful handloading will contribute to better accuracy without a lot of cost.
The .300 Weatherby is a great long range caliber - the secret to using one well is lots of practice (or any caliber for that matter). I wouldn't worry about 1/2 minute accuracy - most critter targets offer vital zones that are much larger than 1/2 minute out to very long range.
Shoot a bunch and learn to call wind. I don't wish to discourage you, just throwing in my two cents.
ian
