The 330gr Gould HP cast in pure lead and correctly sized is a great bullet for the 1-30 twist ML rifles.

Lyman used to offer the same bullet without the HP. Mold #457192 instead of #457122. They have been gone for a long time (1970s) but pop up occasionally on ebay.

IMO somewhere around 405gr is gunna be the max a 1-30 can handle without pushing the bullet too fast. They might be fine at shorter ranges but as you saw they can start to "wobble" as the range increases.