Kurt ....LONG time ago,saw a drawing by p o ackely ,of a bit for turning barrels w/ out a stdy.....h.s., w/ a deep chip breaker cutfor side rake, & sharp angle ,much like the carbide u modified....... i tried & gave up ..came to conclusion that late model craftsman 12x36 w/ 1/2 in thick bed was too lite .......went back to a stdy.......in 1960's ordered an unturned air ga. blank & it arrived turned to abt 1 3/16 in...REALLY rough turned w/ chatter everywhere......either douglass was in a hurry ,or his lathes were too light.......anyway ,fitted it , as is ,to a DCM sprngfld 03A3 w/ an 03A4 bolt,($14.75 + shipping..how sweet it was!), herter glassed it in an old 06 bull barrel target stock ...to check it out before crafting the "ne plus ultra" ...chambered for 22-250 ,put a 1 1/2in. unertle on the barrel,averaged under 5/8 groups ( bunch of 5 shot 3/8 ones ) w/ routine neck sizing ,....... had intentions of going the full route & making the rifle i always wanted & never could afford......,had a killer blank,going to use spar varnish filler,cut back to bare wood,finish w/ linspeed ,clean up & hand polish & slo rust blue action /barrel..,fleur de lis/carved checkering ,hinged O3 guard,welded sweptback checkered hollow bolt,...sure,......liked it so well ,i busted chucks /crows for a few years & never took it out of the stock (still in white when crows went on the list & we got tired of roast chuck).......have abt a 1800 lb. antique 14 in lathe now ,& if i turn another blank,will see if i can turn w/out stdy......think maybe the VERY sharp angle on ur carbide + the chip breaker rake is the answer......
best wishes
docn8as