It a'int the extractors it's the triggers.
The so called "cassette" triggers will pack up quickly in salt air or fine sand conditions.
That is what makes the older M70s so reliable. The BEST single stage trigger ever put in a sporting rifle. The only one more reliable is the Mauser 2 stage.
IMO all the problems with the Walker trigger can be traced to crud in it.
As for two stage: If it works in the trenches of WW One it will work in any hunting application.
