Load gone to pot

[Toymaker]

Hope this is the right room for this. Its about a Rigby, cap lock, .451 caliber, pure lead 525 grain bullet, my own lube mix, card wad, 45 grains Goex FFg. I've been using this load since 1998 in steel silhouette matches and it's been a tack driver. Suddenly it started hang firing and misfiring. Range tests also showed a keyhole problem. The load is on the razor's edge of ballistic stability, I know. But it worked great. Going back through my notes I find I put in a new nipple (recessed flash-hole) and bought more powder just before the problems started.
I replaced the nipple with a flat base flash-hole and stopped the hang fires and mis-fires. Maybe the powder was made with oak charcoal instead of willow, so I upped the charge 5 grains. Instead of 1 fouling shot it takes about 10 shots before it starts grouping. Where it would give me a 50 cent sized touching 5 shot group at 100 yards it now gives me a 3 inch group.
I'm thinking of going to FFFg powder but thought I'd put the situation out and see what others think may have for solutions.
BTW - I don't want to increase the charge too much. Been there, done that, got the bruises. At 65 grains FFg it's like holding the southern end of a north bound mule.

[telebasher]

Might check the hardness of your lead, sounds to me like maybe you got some harder lead and it is not obturating and filling out like it should. This might explain it needing many more fouling shots to foul enough to get some degree of accuracy. Just my thoughts FWIW.

[Mk42gunner]

I'd try another can of powder, hopefully of a different lot number. You mentioned two things that changed your conditions, the new nipple and new powder lot. You changed the nipple and corrected some of it, now change the powder.

Robert

[Toymaker]

Because I shoot a lot of black powder I buy in 25 lbs bulk bags. So I can't really try another lot of powder as suggested by Mk42gunner. However, I DO have that note in my book so the next time I buy powder I'll check and make sure it's a different lot.
I went to the range yesterday and tried a 40, 45 and 50 grain charge of Goex FFFg power. The 40 grain load was pretty good but I had the feeling I was running on the ballistic stability razor's edge again. The 45 grain was better, which made me feel better about that load. The 50 grain group opened up considerably. So I went back and shot another group with 45 grains. Durn if it didn't duplicate!!!! Then I got into the bottom of the shooting box and found the "proof" target from 1998 where I used 45 grains of Goex FFg. Durn me! I was looking at three identical groups except the 1998 "proof" target was 5 shots and the two I'd just done were 8 shots. I think I found my new load!!