336SC,
Let me preface this by saying I have limited experience with the 225GK having only shot 3 animals with it and a brother that shot a hog with the same load.
With that said, the performance of that bullet out of my 358 has been nothing less than awesome. The first deer I shot with it was a doe that weighed anywhere between 120 and 140 lbs. She was standing broadside at 90 yards. I put the hairs on her shoulder and at the shot she collapsed and was probably dead before she hit the ground. When I field dressed her it appeared like there was some serious expansion going on, as the enterance hole into the chest cavity was the size of a golf ball. The heart was intact but there were no distinguishable features regarding the lungs. They were the "bowl of jelly" that we sometimes see. The bullet continued through the off side shoulder and exited the animal with a nickle size hole. To say the least I was very pleased.
The second doe was quite a different story. She was quarterig too me at 173 yards. I was also elavated up on a hill side shooting down into a hay field. The bullet hit her on the leading point of her front left shoulder. She jumped, spun, ran about 15 yards then slowed to a drunken walk until she fell over. The bullet broke the on side shoulder penetrating through the lungs and exiting the animal in front of the paunch. There was little sign of bullet expansion. The lungs had a neat little 35cal hole through them with about a quarter to a half an inch of blood shot tissue surrounding the hole. I contribute this lack of expansion to lower velocity at that distance and lets face it a 120lb doe does not offer much mass to help open that bullet up.
The third animal was a little six point. 45 yards broadside/downhill. At the shot he also collapsed, and the internal damage was much the same as the first doe mentioned above.
My brother shot his hog at 105 yards. It was quartering away and slightly up hill. The bullet entered behind the last rib on the left side and exited the animal between the neck and the right front shoulder. He said it dropped squeled and that was it.
Before loading this bullet for the 358, I too had read problems of Jacket-Core Separation pertaining to the Sierra's. I figured since that bullet was designed for the Whelen, it would be just fine for the slightly lower velocity of the 358 Win. I have no experience with the smaller caliber sierra's so I can't speak to that. However I do believe when it comes to that issue of Jacket-Core Separation, it is as much a matter of velocity as it is bullet construction. Put a .277 130gr game king on the shoulder of a white tail at 40 yards with a striking velocity still 3000+ fps, that is asking a whole lot of bullet that has no mechanism to lock that core into the jacket. Now put that same bullet on the same shoulder of that deer at 350-400 yards when it has had a chance to slow down to the mid 2000's fps I believe it would be a totally different story.
I know that was a long winded response, however I do hope it shed some light on that 225 Sierra. I would not hesitate at all to use it again. Its very accurate and with the velocity produced by the 358 Winchester, it is a winning combination.
Flinter 54