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https://www.trademe.co.nz/sports/hunting-shooting/reloading/other/listing-3133234397.htm?rsqid=22e636c383dd4a84b689f44a45c1e92a-001


might be worth it to give you KNOWN DATA...

I can tell you now,when that slug was bouncing around woolshed walls n rails I WAS FAIR CRAPPING MY DAKS.....NOT recommended.

you could be pushing poop uphill till you source another powder perhaps....

AP-70N appears in my old paper ADI book 3rd edition november 2000
cowboy shotshell data all loads shown are 1200fps at slowest,
winchester compression case.win 209 primer WAA12 22grn AP-70N
...

lyman #5 says DO NOT reduce by moree than 5% in the buckshot/slug text....

if he knows how to clean gun...and looks after it...black powder would do it really easy as it wont be much above 1100fps now.

find a round ball of correct diameter...and be aware,and make sure to tell you mate...shotgun slugs BOUNCE like buggery if hit something hard,slowing them down will make it more so....many years ago...