Re: 300 Weatherby Load Help
I have to agree with kraky on the bullet seating depth issue. With the freebore in the Weatherby, it is likely not possible to seat the bullets very close to, or on the lands so you may as well keep them short. Another point of concern is that you have the barrel floated. It has been noted and discussed on other threads here, that the Weatherbys actually have a designed pressure point at the front of the stock. I don't know which Mark V you have but in my ULW, I had to remve a little bit of that pressure point to decrease the pressure on the barrel. It shot near MOA prior to this and with a little trial and error of filing down those pressure points, I improved that by about 50%. I do think that perhaps the very thin profile of the lightweight barrel is a bit more susceptible to these changes than a standard barrel.
I have actually never shot nor loaded any bullets as heavy as you are looking at for this caliber. I usually shoot 165 gr. I have used the both the Swift Scirroco and the Nosler BT with great accuracy success. With how the Swifts have performed on elk, I have not considered looking to heavier bullets. The two best powders I have used are H4831SC and H1000. Both loaded to near the top of typical recommended loading have been good (under .75 MOA). I have played a little with a couple of the VV powders as they have tended to be very good for me but haven't gotten too serious about getting the best loads out of them yet. With as much more expensive as it is for me to get the VV powders, if I can stick to Hodgdon I would prefer that. Though I do consider the expense well worth it if they are the best for getting a particularly finicky gun to shoot well. Good luck - I do think your gun is capable of more than you have seen out of it to this point.