7.62X39 vs 300 Whisper capacity

[leadman]

Awhile back someone posted they thought the difference in capacity between the 7.62X39 and the 300 Whisper was only a few grains.
I was processing some 7.62X39 tonight and thought I would check out the difference. I used WC680 as it is the original powder for the 7.62X39 and works well in the 300Whisper also.
Filled to the neck the 7.62X39 holds 30 grains, the 300 Whisper held 19.3 grains.

10.7grs. is a significant difference.

[Silvercreek Farmer]

Along these lines, would a subsonic 7.62x39 cycle an AK? Perhaps you would need a lighter spring?

[thehouseproduct]

Along these lines, would a subsonic 7.62x39 cycle an AK? Perhaps you would need a lighter spring?
I didn't have trouble getting the 200gr Lee boolit to cycle subsonic in my AK with stock springs. The thing I have found is that people are hung up on using pistol powders. I used a smaller charge of fast rifle powder (2230 or Xterminator) for good results.

[KTN]

Along these lines, would a subsonic 7.62x39 cycle an AK? Perhaps you would need a lighter spring?

Loaded with 13.9 grains of Vihtavuori N130 and Lapua D166 200gr FMJBT, my Sako M92S cycles perfectly, velocity is 1000 fps and accuracy close to full power 123gr FMJ loads.


Kaj