260 or Creedmore?

[stickflickin]

I am building an AR10 platform rifle for long range. I am starting with an Anderson M5E receiver / foregrip assembly. The lower is an 80% Arms that I have. Ill probably go with a Rainier ultra match barrel. Haven't decided for sure, but it will be from one of the top manufactuters.

I have read a lot about these two calibers. From what I understand it is a six of one half dozen of the other situation. The Creedmoor May feed slightly better but 260 is supposed to be acceptable and may have a slight ballistics advantage for reloaders. I'm leaning towards the 260 because I have a lot of 308 national match brass. All experience based input is much appreciated.

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[DirectDrive]

I don't have either, but from what I gather...
260 is just 308 necked down....no deep thinking there.

Creedmoor was developed to handle VLD bullets in a short action, which is what AR10 could be called.
The mag box length being the driver.
Designed with precision shooting in mind.
6.5 bullets fly so well because they're extremely long (high BC) and with 260 they have to be set deeply into the case, which is not ideal.

Also match grade Creedmoor ammo can be had off the shelf.
My Aero large frame receivers will be built into a Creedmoor.

 

[B5Ben]

Creedmoor has more support at this point, and Im not sure that will change any time soon. Kinda like the Blue-Ray and HD DVD or whatever the other one was called, IMO. Both are great and you probably wouldn't notice the difference if you had both side by side, but the winning factor for me is that ammo 6.5 Creedmoor is probably in stock somewhere nearby, and therefore there is brass to be had for loading. I haven't seen much in the way of factory support for the .260. My PA-10 will be going to 6.5C shortly as I have brass and dies waiting for a barrel.

 

[Kruel J]

Creedmoor, as stated above.

 

[stickflickin]

So to go back to an important point that i made in the OP, I have a lot of 308 NM brass. That is what was causing me to lean toward the 260. What i am picking up from reloading and long distance forums is that some people are loading both to an OAL in excess of 2.8" and even more than 2.9" with some bullets. The max functioning OAL for an AR magazine is 2.80" - 2.82" from my research. If all of this is true, AR shooters may be limited to OAL by the magazine for both rounds. Maybe I am putting too much value in the unproven NM cases that i have yet to load. This is a good summary
Bullet Point Ep 20 260REM vs 6.5CM

 

[Kruel J]

I read the article, and if all you care about is reloading and factory ammo isn't even a consideration then you already have your answer. As far as accuracy and ballistics, it's mostly a wash. Decide what's more important to you.

 

[orygun]

I'd pick the Creedmore, especially for longer ranges. The 260 is a very good round, but does require a long OAL to keep the case mouth off of the ogive of a VLD type of bullet.
Other than that, I believe that the 260 is being left behind. The Creedmore has some to do with that, but the excellent 7mm-08 put the 260 on the back burner, kind of like the 243 vs Remington's 6mm way back whenever.

 

[ThemGunsThough]

Creedmoor because YouTube did all the convincing I need.

 

[P7M13]

If you have lots of 308 NM brass, why not build a 7mm-08?

 

[orygun]

Or why not build a 308? Honestly, while I was trying to go along with the OP's line of thinking, I'd not build an AR-10 rifle that's less than a 30 cal.

 

[PaulB47]

the excellent 7mm-08 put the 260 on the back burner

7-08 was released long before the .260 was.

As far as wind is concerned, what the .308 will do at 800 yards, the 6.5CM or .260 will do at 900. Is it worth the extra 100 yards? The only real problem with .308 is that it is boring.

6.5CM seems to have the momentum these days. That is telling since it came from behind.

 

[BlackdogGS]

Having thousands of 308 brass laying around shouldn't be the deciding factor. You could easily use that brass or sell it. Personally I'd go Creedmore.

 

[Certaindeaf]

.243 Win!

 

[No_Regerts]

So to go back to an important point that i made in the OP, I have a lot of 308 NM brass. That is what was causing me to lean toward the 260. What i am picking up from reloading and long distance forums is that some people are loading both to an OAL in excess of 2.8" and even more than 2.9" with some bullets. The max functioning OAL for an AR magazine is 2.80" - 2.82" from my research. If all of this is true, AR shooters may be limited to OAL by the magazine for both rounds. Maybe I am putting too much value in the unproven NM cases that i have yet to load. This is a good summary
Bullet Point Ep 20 260REM vs 6.5CM

A 260 will have to be loaded to max available OAL because of the case length. The 6.5 CM, with its shorter case, gives you more latitude. 2.8 with a 260 may not kiss, but 2.8 in a 6.5 CM likely will because more of that 2.8 is exposed bullet.

 

[CHLChris]

They just released a 6 Creedmor, too! But back to the .260/6.5... Is 6.5CM just the new hotness? Is it going to stand the test of time?

 

[No_Regerts]

They just released a 6 Creedmor, too! But back to the .260/6.5... Is 6.5CM just the new hotness? Is it going to stand the test of time?

One reason I think it will stick is that its decent performance without the recoil or fuss of a magnum. Its entirely practical and inexpensive to shoot.

 

[Greenbug]

If you are spending the money/time on a custom barrel, why not a custom chambering?
260 Ackley might be an option you have not thought of....

I had mine built as a hunting rifle back in the early 2000's with a Lilja barrel 1:8 twist 24" on a Remington Model Seven Action.

It shoots sub half MOA with Nosler 120 Ballistic tips at 3120 FPS. It reaches out there pretty good and lays the smack down nicely.

 

[WWShooter]

Apparently (based on internet searches both for the issue and to confirm that it's real) the currently available brass for .260 (Lapua and others) is much better for reloaders than the currently available brass for the 6.5 Creedmoor (Hornaday or Norma).

Full disclosure, I'm a .260 reloader.

 

[Greenbug]

Anybody have good chronograph data on real world 6.5 Creedmoor loads? I have a hard time believing published muzzle velocities on the box of ammo. Barrel length and bullet weights and speeds from ammo shot over a chronograph would be nice to see and compare to my own 260 Rem and 260 Ackley data.....

I am suspicious that the muzzle velocities published for 6.5 CM ammo is "optimistic" or a clever marketing ploy.

Anybody have real world no BS data they would be willing to share?

 

[WWShooter]

I've got .260 data out of a 20" barrel. Nothing in 6.5 Creedmoor.