You have to remember that the Sendero is a Remington 700 as well and has essentially the same action. The only diffrence being the Finish of the rifle and the Stock. You did fail to mention if the countour of the bbl was the same. I have seen a SPS with a bull or heavy bbl, but usually in the Short Action Format.
If yours has a bull/heavy bbl, then it is a Sendero without the more expensive stock.
However, there is no reason that a standard countour rifle couldn't shoot as well as a heavy bbl rifle. I happen to have a .243 AI in a standard countour 22" bbl that will out shoot a lot of varmit rifles out there.
Most guys who like rifles with heavy bbls like them for the steadyness that they have, they are easier to shoot prone or off of a bipod and the recoil is more manageable, they shoot bettter off of the bench and for those who will shoot extended strings, they don't heat up as fast, but when they do heat up, they take longer to cool down.
They are heavier to pack around and aren't what you would call a "mountain" rifle or even a sheep rifle. I'm one of those who prefers a heavy bbl and I get a lot of flack about it. I carry my own rifle, and don't ask any one to be my gun bearer, so that being said, If you like the heavy stuff, you'd better be willing to carry it.
I like the absolute assurance that my heavy bbl rifles give me, I know exactly what they will do with the first shot and that gives me confidence. I also seem to shoot them more and that helps me when I hunt as another confidence builder.
I would would also suggest that you look at the lugs of your bolt to see if they are properly contacting the lug recesses and lap them, a trigger job would certainly help. You did the right thing with floating the bbl and bedding the stock. If you decide to ever rebbl the rifle, I'd then "blueprint the action" and get a really good bbl.
Are you handloading to to optimize the performance of your rifle??? That certainly goes a long way as well.
Hope this helps
Dan