There were some great heavy for caliber bullets made up by the original owner of Wildcat Bullets in Canada, for both calibers and plenty more. Unfortunately for a bunch of us he ended up shutting down and selling everything to another fellow here in the states. That said the new owner concentrated on the heavier 7mm bullets in the beginning, with promises of getting into other calibers, which never seemed to come about. I sure wished I had ordered a ton more of the heavier .257" ones myself, when the original owner had Wildcat up and running.
As for the Matrix, I am hopeful that I will have some spare funds available in the near future to pick up some of his heavier .257's. I can at least compare them to the Wildcats I have left to see how much differences there is. I am however looking forward to giving some of them a ride as soon as I can manage to figure out how to get them paid for.
For the most part however in .257, your going to top out in the 125gr range for customs as most folks shoot a 1-10 twist and most don't want to make anything heavier due to that. My 25-06 AI is a 1-9" so up to 130 isn't much of an issue. That said I am getting plenty of performance from the 120's now so I am not sure how much better I can get going heavier other than a tad more weight down range. I built the AI version with a 28" finished length Broughton 5C to get all I could get from it and still have a rifle that was fairly easy to get around with. It will easily get 3350fps with the 120gr weight bullets with a decent charge of Ramshot Magnum.
My suggestion is if you try the Matrix, and they shoot up to your expectations in either caliber, purchase all you think you will need, as if they shut down there may or may not be something to replace them. Been there done that. As for the B.C. that will depend on your final load and your standard conditions. When my friend and I were loading the heavy .277-169.5, and 195's in our .270 AM's we were getting great numbers, but down here in TX we couldn't get close to the numbers of the folks up in the high country. Simply ain't gonna happen when you have an average 65-70% RH and temps to go with it. Even so we still got great groups and the performance was nothing to throw rocks at what so ever. Either way you look at it, you are only going to get what you get, no matter what is presented on the cover. While Berger is a great company and builds great bullets I cannot get the BC they rate their bullets for either so I just pick what i want to shoot and work the loads up accordingly.
If I ever move to a higher drier climate I might worry about those numbers but for the foreseeable future I just worry about which one shoots the tightest.