Was using RB brass, 5.5 Grains of Unique, CCI primers, and Hunter Supply 200Gr LSWC.
This one ?
If so, and if seated to depths similar to Lyman's #452630 ~OAL: 1.235,
... then Lyman#49 has a UNIQUE
charge range of
6.0gr (717fps/11,700cup) to MAX:
If you were really running 5.5gr Unique behind this bullet and at those seating depths, I now understand why you were having function/feed problems. (and if you were using a factory standard/hardball recoil spring instead of a 12# wadcutter spring,* you never had a chance.)** That said I'd sure feel more comfortable if you could find/use a chronograph to work toward the higher end.
** You may also find that the other magazines begin to properly function with the higher power loads, and/or with a different reduced-power recoil spring.