Burrdock, just a couple humble suggestions for you. before going and spending money on the rifle, could you have someone else with more shooting experience shoot the Sendero? this may offer some insight into the capable accuracy of the rifle with this ammo. Possibly the rifle simply doesnt shoot this particular ammo well or will need some work to get it shoot. A more experienced shooter could also coach you for a better shooting routine which will improve your accuracy with the rifle over time. Proper practice is important for consistency. poor practice simply will create bad habits that will be difficult to break.
I have yet to find a Sendero, old or new that would not shoot at least a few types of factory ammo decently. As mentioned, handloading consistent rounds that are matched (worked up) for the rifle will definately be something you should look into. This will be one step in getting the absolute maximum accuracy and consistency out of the rifle. Trigger tuning, skim bedding the HS stock or full bedding job on the replacement stock and other mods will squeeze every last ounce of accuracy out of it, but nothing beats good practice to take full advantage of any and all mods. JMHO but I would learn to shoot the rifle to the best of your capabilities and the rifle capabilities before dumping a bunch of money. take care
Cody