.223 Sub Sonic

[Treeman]

The reason for heavy bullets is that lighter bullets need very small charges so as to not exceed the speed of sound. The extra weight of the bullet needs more oomph and charges then increase in volume and tend to give better consistency and then accuracy.

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Which is the exact opposite of hyper sonic reloading where heavier has less charge than lighter bullets

[Tripodmvr]

The reason for heavy bullets is that lighter bullets need very small charges so as to not exceed the speed of sound. The extra weight of the bullet needs more oomph and charges then increase in volume and tend to give better consistency and then accuracy.

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Which is the exact opposite of hyper sonic reloading where heavier has less charge than lighter bullets

Correct yes. The whole exercise of going subsonic is a field of its own. The rules that apply are such that it needs careful study and following the recipes that have been found to be safe through practical experimentation.