It is not weight, but length that determines stability.
In a 1 in 12" twist 223, you should be able to stabilze the 70gr Speer semi spitzer, but probably not the 62gr Speer FMJ boat Tail.
I would think any 70gr and under semi spz flat base bullet or shorter should stabilize.
With boat tail bullets I would think 55 gr is about max.
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