Also I found 777 209 primers do not work well with the Endeavor barrel, and had to close the break action pretty hard or the hammer wouldn't click back.
I picked up some Remington 209 primers, which worked fine and seem to have better results with accuracy too.

Also the new style breech plug on the Endeavors are awesome!!!
The mess is decreased by at least 50% and is much easier to clean than the 209x50 mag barrels.

I'd give it 3 thumbs up, but I only have 2 thumbs...!!!