The ffg American Pioneer Powder (APP) has a
very chunky granulation. It's chunkier than any other ffg powder and probably works better with inlines that use a #209 shotgun primer.
The APP fffg does flow better from a flask & measure better.
I don't want to discourage you from using it but if you could switch it with a container of APP fffg it would probably ignite more reliably.
Using CCI #11 magnum percussion caps may help to ignite it since the flame may need to travel further up the flash channel to reach the chunks to set it off.
Also, keep the container tightly covered because it can easily absorb moisture from humid air and go bad.
I use the APP fffg and haven't had that happen but it has happened to many others.
Because of the chunky granulation it's almost like using 10 grains less of other powders.
But otherwise the APP fffg does work good and produces plenty of power.
If you do experience a misfire, dribbling a few grains of loose powder under the nipple should help to ignite it, but the larger chunks won't fit under the nipple as easily as with smaller granules. If it happens you'll see, and I hope that it doesn't cause any ignition problems with your new TC Hawken. It's hard to predict if it will matter or not.