Unless you plan on using Pyrodex pellets, you are better-off staying with hot #11 nipple & magnum #11 caps that produce less scope blowback & less crud buildup with 777 loose powder. With this 209 conversion -- which is better than the Remington conversion, posters reported 777 pellet success using ultra-hot, Federal 209 primers.

Caution: Cover your scope bottom!

Cabelas Remington 700 ML 209 Breechplug Conversion