A few years ago, I started playing with 6.5mm cartridges and rifles. I have experience with the 6.5x55, 6.5-284, and .264 Win Mag. Based on my experimentation, here are my conclusions:
I consider the 6.5x55 to be the king of the smaller cased 6.5's. It is my favorite 6.5 for all-around use. The other smaller cased 6.5's (.260, Creedmoor, 6.5x47, etc.) are all basically designed to get 6.5x55ish performance from a short action, which, IMO, is about the only practical reason to consider any of them over the 6.5x55. Since I am not one who favors short actions, I prefer the Swede. Loaded to its potential in a modern action, the ol' Swede will outperform all of them (while giving the much hyped 6.5-284 a run for its money, but more on that later). Lapua brass for the 6.5x55 is available and at half the price vs .260 Rem, 6.5-284, or 6.5x47.
The 6.5-284 is a nice cartridge that has all of the inherent virtues of the 6.5's. It is mild to shoot, easy to tune, has high quality components available, and is reasonably fast and flat shooting. I went to the 6.5-284 in a quest for a fast 6.5mm. In that role, I found it to be underwhelming. Even using Lapua brass, the rebated rim cartridge design has the un-nerving tendency to show pressure signs early. Shot side-by-side with a modern actioned 6.5x55, there was about a palm width difference in trajectory out to 600 yards and no detectable difference in inherent accuracy. Not enough to justify the step up, IMO.
To be fair, I think the story MIGHT have been a little different if I had paid more attention to throat length when it was being built. I specified 6.5-284 Norma, but the OAL to the lands of 3.092" with VLD's tells me the chamber reamer was probably a 6.5-284 Winchester spec reamer, which probably cost me some useable case capacity vs the 3.228" spec of the Norma version. THAT is something worth paying close attention to for anyone considering a 6.5-284. The 6.5-284 is a GOOD cartridge. It just wasn't what I was after. I didn't feel it did anything that couldn't be done just as well (and at less expense) with a comparable 6.5x55.
Then came Winchester's re-introduction of the Model 70 in .264 Win Mag. I HAD to have one and paid a premium to get my hands on one of the first few to be available. It was worth EVERY penny, IMO. Had this rifle been available earlier, I would never have built my 6.5-284. It was everything I was looking for in a fast 6.5 for the hunting fields. I had no trouble getting speed AND accuracy from this setup. The .264 responds well to being downloaded to 6.5x55 velocity (which I did for a hunt in the Kentucky woods), while having enough throttle to approach 3200 fps accurately with 140 grain bullets and Retumbo or RL-33.
The .264 heats barrels quickly and is obviously not a good choice for high volume or casual target shooting. As a pure hunting cartridge, it is by far my favorite 6.5. It is such a pleasure to shoot, though, that one has to resist the temptation to plink with it. IMO, if you plan to own a .264 Win Mag class rifle, it is a good idea to also own a smaller cased 6.5 for more general use.
If you are going for a factory 6.5, I believe a Ruger in 6.5 Creedmoor is a good option. Because I prefer the 6.5x55, though, I believe the Tikka T3 Varmint might be a better option. I don't personally have experience with the Tikkas, but they seem to have an excellent reputation for accuracy out-of-the-box. They come from the factory with an 8 twist (a lot of factory 6.5's have 9 twist barrels), which makes them able to handle all of the best 6.5 bullets made. Put a good scope on it, feed it Lapua brass and good bullets, and I don't believe you will need to do anything else to the rifle.
My Winchester Model 70 in .264 Win Mag is among my favorite rifles. If you go the Model 70 route, and want something other than walnut and blued metal, I recommend you go with the most basic model you can, put a barrel on order from the maker of your choice, and order up the stock you want, too. Then, shoot the heck out of it in factory form and enjoy yourself while you wait. When your aftermarket parts arrive, send it all to a good gunsmith to be put together, making sure to tell your smith you want your new barrel Melonited. The Model 70/semi-custom route will be more expensive, but the result will be very worthwhile and will last a long time if you don't give in to the temptation to plink or shoot varmints with it.
