Originally Posted by Buffalobob
An object will tend to achieve a minimum energy configuration. A partition achieves that through the deformation process as is shown in the picture. How your bullet does it I do not know but I doubt that it is consistent. The reason long VLD bullets require fast twist barrels is that flying point first is not a minimum energy configuration therefore energy must be added to prevent it from achieving such a configuration. The bottom line is what does one wish for the bullet to do once it has expanded.
I personally do not mind tumbling bullets because that is what we used and that makes a non-expanding bullet cause a larger wound channel (with less penetration). However one simply should know what a bullet is going to do before using it for serious work. Having been down the road with semi wet newspaper I don't do that anymore being as the result can be very misleading.
Both in wet news-paper, water-jugs, and correctly calibrated gel, the MK318 MOD0 SOST ammunition will fragment very shortly after impact. The front half of the bullet will become a snow-storm of lead and copper, and the back half (solid copper) will continue forward with minimal radial expansion (more or less, depending either on flesh or wood or whatever it hits) like the solid copper wad-cutter it has become. Not enough people have yet been shot with it to say what it does to people, at least, enough people to get back to me.
The MK318 MOD 0 SOST is not dependent upon yaw to fragment. It performs reliably out to 100m from a 10.5" barrel. Its performance is much more predictable than M855, which it was designed to replace.
I do not understand what you are trying to say when you indicate to me that a 30gr copper projectile will penetrate a shallower distance than a 30gr copper-jacketed projectile (meaning, the base of the SOST vs. the base of a Nosler Partition.)
Their meplat diameter is assumed the same, and their weight is the same. Penetration should be identical.
However, your Nosler partition is a hunting bullet, so instead of fragmenting (one hopes...) it will expand. It is not like the SOST at all, in this regard, which is designed to rapidly fragment, shearing at the first band as I have pictured. Every single bullet I have recovered from every medium I have shot, as well as every picture of every single bullet recovered that I have seen, shears at this point. Looking at the cross-section I took of the bullet, this is easily explained.
The SOST does what it was meant to do: Rapidly fragment WITHOUT having to first yaw, and yet provide good penetration afterward, and against barriers such as glass, car-bodies, and the like.
If it helps, think of a Speer TNT 30gr Varmint bullet stacked on-top of a 30gr solid-copper wad-cutter. That is how the SOST performs, in the simplest of terms.