I apologise for getting on the black powder soapbox. I was just trying to point out that there are other options, that will shoot without a crud ring that will enable an inline shooter to practice & hunt if BH209 is not available.
If I was an inline shooter, as the supply of BH209 opens up, I would have both black powder and BH209 in my stash. Black powder has an unlimited shelf life as long as it is stored in a cool, dark place, preferably temperature & humidity controlled.
From what I am learning here, BH209 has similar long shelf life properties. If any of the other black powder substitutes have long shelf lives, then I would add those to my list of propellants to keep on hand in case of another national shortage like the one we are trying to come out of now.
No sense in getting stuck with nothing to shoot/hunt with.
For those that might think that because they shoot real black powder they are safe from a powder shortage/ban, especially those that favor the flintlock (like myself), I would also give some thought to having some of the substitute powders on hand if they had acceptable shelf lives.
Herb, over on the ALR forum tested every black powder substitute in his scratch built, .58 caliber, flintlock, Leman shorty rifle with a 1.0625" × 24" long straight octagon barrel. This was about a year ago. All he did was duplex a 10 grain charge of fffg Goex under the substitute powder that he was testing. And, of course, he needed real black powder in the pan of the flintlock for a priming charge.
I won't swear to it, but I do believe he shot & chronographed, Pyrodex, PyrodexP, Black MZ, Golden, Triple777, & BH209 against Goex, Olde Eynsford, Schuetzen, and Swiss.
Because of his age; his history working with Doc White as an original employee at Green River Rifle Works; his knowledge, authorship, and ability to scratch build historically accurate Hawken rifles; and the fact that he told the moderators at ALR right up front in the OP to NOT give him any grief about posting information on black powder substitutes; such useful information about subs in a flintlock are out there for anyone to look for.