Re: Building a long range rifle with a used action.
Control round feed actions make excellent hunting rifles. The non rotating extractor acts as a gas check in the event of a violent case rupture and the significant amount of case purchase makes for powerful primary extraction of a case. It also makes for very robust and reliable feeding when properly done.
That being said I would edge towards the Remington for a rifle being purpose built for long range shooting. The historical performance is well documented and leaves little for debate. Other advantages include improved bolts, fire controls, triggers, and other accessories.
As for extraction. In my humble opinion a Sako extractor is the LAST thing I would consider adding. One cardinal rule in my shop is I won't have anything to do with them. It's nothing personal. The Sako extractor was never designed to work in a twin lug, 90 degree turn bolt action. When the bolt is in battery the extractor is almost completely exposed by the ejection port side raceway. Considering the extractor is only retained by a spring and plunger it leaves little assurance that it will stay put in the event of a violent case rupture. This isn't to be taken likely. I know of two cases personally where this began on the range and ended in recovery from surgery.
A better alternative is the M-16 style extractor. At least it has a pin for retention. That being said there's really nothing wrong with a factory Remington Extractor. Some go so far to say that they are stronger than the Sako's/M-16's. I can't speak from personal experience as I've never done a test.
Just things to consider.