Hold on dvdegeorge

I don't recommend those 410 primers with 777 pellets. You never stated that. They (209-410) may not have enough juice to ignite on moisture-driven huntin' days with 777 pellets.

Real blackpowder is the easiest to ignite in loose. Just about any loose powder (aside from FF American Pioneer/Cleanshot) will ignite with 209-410 primers.
With pellets, Pyrodex includes a small amount of blackpowder-like substance to enhance ignition. That's why they want you to place the dark side of the pellet down the bore first.

777 pellets (as of today) offer no ignition enhancers (and) if you read their literature, they tell you their powder is intended for "modern" muzzies... not sidelocks. 777 FFF loose works well in sidelocks but FF is " touch & go".

Anyways, that's an indication that 777 needs a higher temperature to ignite. Remington 209-410 primers offer a very cool ignition. They may work in your situation... but I wouldn't bet on it 100% of the time.

If you plan on using 777 pellets, I recommend the hotter Remington STS 209s, Winchester, Federal, RWS, CCI-Magnum. If you ever switch to Pyro/777/Blackpowder loose, the cool 410s will work nicely.