Well , I personaly think that the 6.5-300Win would be the better choice due to the better bullet choice, the 140 A-max is a hard bullet to beat in the long range hunting area in that caliber for deer sized critters and the 140 Partition is another good bullet for bigger game AND Nosler is comming out with an Accu-Bond in the 264. Another point is that the 264 bore over the 257 bore will offer a better bore to powder ratio meaning its a little more effecient.
I would still stick with the rounds based on the 300 win because of the better brass available , if you don't mind paying a $1.25 per case then you have access to some awsome brass from Lapua.
JD makes a good point about the great bullet selection for the 6.5/.300; along with the bullets he mentioned, this cartridge would probably work well with one of the heavy Wildcat bullets. The 6.5’s generally have good sd’s & bc’s, thus contributing to its long-range potential. The Weatherby is one of my sentimental favorites, but with the correct twist the 6.5/.300 should prove to be an awesome choice.
The 6.5 would be better ballistically thats for sure. Its either you like .257" cal which doesn't have all that great BC"s, or you like .264" cal which has great BC's. I personally like .257 bores, but I know ballistically .264 is and will always beat it. Example being my 25-06, I love it, but when it comes time to rebarrel, basic instinct is telling me 25-06, but in the back of my head I know the 6.5-06 is a lot better with the 140g type target bullets. You can use heavy .257" caliber Wildcat bullets, so that does add some versatality though.
Have a Merry Christmas by sending Richard Graves an email and asking him what Santa is bringing us good little boys who like the 257 Wby. Clay Spencer is thinking that Santa will leave a 1-8 twist 257 button in his stocking so he can make a certain unnamed individual a special barrel to shoot some special bullets from north of the border.
As a note- The case capacity of a 257 Wby is 84 grains, a 264 Win mag is 82 grains and a 300 Win mag is 88 and probably by the time you neck the 300 down it is the same as the 257 Wby and 264 Win mag. It is unclear what you gain by going the wildcat route.
Your really splitting hairs here. The 6.5-300 will have an edge performance wise but not by a drastic amount.
If you look at the best bullets in each caliber, its pretty close to a dead heat as well. Comparing a 156 gr ULD RBBT 25 cal wildcat Bullet to the best 6.5mm bullets made by the commercial companies is not really a comparision. The big Wildcat will get you BCs in the .8 range. In my 257 AM I use .82 to get my ballistic program to match up to actual bullet flight.
That said, I just got some new 168 gr ULD RBBT 6.5mm Wildcat Bullets that look extremely impressive. These were made with a die that will not be used on the production bullets and as such the production bullets will have a higher BC rating which should be slightly higher then the 156 gr 25 cal bullet.
These are the heavies of the heavies though. The 6.5mm family has several very good quality 140-142 gr class bullets. The 25 cal only has one bullet in this range in the 142 gr ULD RBBT but its a hell of a bullet.
So the 6.5mm does have an advantage on selection but as far as the best bullets out there, the 25 cal has bullets that will top any conventional 6.5mm bullet until you get into the real heavy custom bullets.
I will be testing the new 168 gr ULD RBBT in a Lilja 1-8, 3 groove chambered in 6.5-284. If this rifle stabilizes these bullets, anything of this size or larger will with this twist. We will see.
TO be honest, I would probably opt for the 6.5-300 just because I am not a Wby fan but it has nothing to do with bullet selection to be honest or really performance.
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.