So.... today i shot my Lyman GPR with the same powder i was using in the fowler. 10 shots without any hesitation. but i had kept the powder in by the stove at 16% humidity last night so i decided to retry the fowler. got it to fire once in 5 try's so got savage with it.
after cleaning i disassembled it and drilled the vent out, tapped it and installed a Ox-yoke liner. ran the bore scope down its gullet and saw a large bur on two sides of the liner, and the liner protruding into the bore.
pulled the breech plug and GASP! dremeled the bur and liner flush with the bore.
put it all back together and loaded it with 90g of ff. flash in the pan. picked the vent deep and next time it fired. OK............
light bulb went on and i next loaded it with 10g ffff with 70g chaser of ff. 10 shots in a row with no glitch.
So............. i tried a load of ff only. FIP!
back to duplex and it fired every time.
between the GPR and the fowler, i emptied my flask. i think i have it cured.
i didn't shoot the fowler for accuracy today but did so with the GPR.
the more i shoot that gun the more i like it.
all shots from a bench. ten shots total