Stuck Muzzle Loader Breech Plug

Well, I can't believe it happened, but it did.

I clean my muzzle loaders after each and every use. I remove the nipple and remove the breech plug once a year or so, lube them, and replace them -- same as my shotguns.

I shot my Knight Bighorn stainless steel in-line 50 caliber yesterday to sight in a new scope. I went to clean it today. The nipple came out fine. The breech plug won't budge.

I tried "Liquid Wrench" by spraying the breech plug down and standing the barrel vertically for about 30 minutes. No dice. Knight has a special tool for removing the nipple and plug with holes in it for "extra torque" if needed. I used an Allen wrench in the hole -- no movment. Rapped on the Allen wrench with a wood 2x2. No movement. I then bent the Allen wrench by putting an extension on it. Still no movement.

I then tried WD-40 for 30 minutes. Same steps, same deal. Bent a different slightly thicker Allen wrench ... the thickest I could get into the "extra torque" holes Knight provided. No movement.

GRRRRRRRR. When my buddy bought a used 10-gauge and we found the choke tube stuck when we got the gun home, these techniques loosened it up.

Now I am letting this thing soak overnight in WD-40.

I finally found a round this gun likes and it is shooting 5-shot nearly-one-hole groups at 50 yards. I want to keep it.

Anything else I can try?