Now that's impressive!If it is still up, JD Jones owner of SSK Industries and inventor of the 300 Whisper posted his work up load data, on line, for the 300 Whisper development for the military. Of course the 300 W is the pre cursur to the 300 BO that Bill Anderson came up with, maybe in order not pay JD royalties on the barrels or rounds JD may have developed, etc, etc.. The 30x221 has a great deal to do with the use of 7.62x39 cases to achieve subsonic loads with heavy bullets. JD used H-110 and 296 to achieve sub 1,000 or 1,100 fps loads with 230s. Their twist rates have gone on up to 6 or 7 as they have some 400 grain body armor penetrating rounds, just uses the body armor as part of the projectile.
This is a picture of my hard cast/ powder coated 300 BO and 358 MGP AR rounds. I have just a few years developing and shooting subs in the AR platform to achieve full function. My speed of sound at my elevation is 1,113 fps. So I do an even 1,000 which the 30x39 can easily do. Oh, that is the 30 cal Lee "Cruise Missile"mould, with shake and bake Eastwood gloss black PC fro car chrome. the 230 grain plain base round nose. Works well but I do like big and slow in subs, for piggy planting, so the 35 makes a bigger hole for the same effort and "price". The MGP is a necked up 6.8 SPC. The 30x39 is in-between in case capacity.
My reloading data is in the shop, but if memory serves the 300 BO load is 9 grains of H-110. So should be 10-11 in the 30x39.
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In case you may be wondering, this is the 6.5 Grendel 160 grain Sub round and the bullet after penetrating 11 FWB phone books and 6" of compacted road bed clay. This was from the first full function AR-15 subsonic in 6.5 Grendel. I used the .267 Hornady Cacarno 160 bullets to get the quick chamber pressure, low velocity. Penetrates like an arrow.
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