.260 Rem or 6.5 Creedmoor?

[1stmarine]

This comprehensive analysis by Zak Smith will help you understand these calibers...
http://demigodllc.com/articles/6.5-shootout-260-6.5x47-6.5-creedmoor/

 

[eastbank]

i have a remington classic 6.5x55 unfired in the box, but these four swedish 6.5x55 rifles are the ones i shoot. i shoot no heavy loads thru them as the 6.5 bullets don,t need hyper-speed to get the job done. eastbank.

 

[cdb1]

If you ever decide to sell the Remington Classic let me know.

 

[Gtscotty]

The 6.5 Creedmoor is a shorter cartridge than the .260. So I'm assuming his point is that you could load bullets with a longer OAL, and still fit in a magazine sized for the .308 family of cartridges. That might be an advantage when handloading the longer bullets, and playing with whether they like a jamb, or a jump, to the lands.

Not to put words in his mouth....but that is what I think he was meaning.

This is the main benefit of the CM over the .260, I'm not sure where the focus on powder capacity intrusion is coming from in this thread. I shoot 6.5 CM, and .308, so I'll put it in those terms. My OAL for my CM with 140gr Nosler CC's is 2.76", 0.02" off the lands. My OAL for my .308 with 168gr Nosler CC's is 2.86", 0.03" off the lands. The CM will feed just fine through a PMag ( which is what I usually use with the RPR) or other short action mag box ( my M70 EWs maxed out at about 2.84"). If I want my
.308 loads to feed, they need to either be in an over sized magazine, or action, which they are, the TRG22 mag my Tikka CTR uses will accomodate 2.9". I've read that loaded to normal mag length with heavies, the 6.5CM has a slight net powder advantage over the .260, but that's not as important to me as being able to get reasonably close to the lands and still feed. If you're using a longer mag/action, there is no real difference between the two.

 

[1stmarine]

There is no COAL restriction for the 260. It works fine with the typical magazines and the best bullets available.
that is why I posted this very nice review from Zak, founder of this forum... http://demigodllc.com/articles/6.5-shootout-260-6.5x47-6.5-creedmoor/
Also the 260 has a smoother angle on the shoulder that is great news for autoloading firearms an in line with military service cartridges following
the same dimensions directives (ie: 5.45x39, 5.56/223R, 7.62x51/308W, 338LM). This is huge for a cartridge to have a chance to be considered
for service use.

 

[Gtscotty]

There is no COAL restriction for the 260. It works fine with the typical magazines and the best bullets available.
that is why I posted this very nice review from Zak, founder of this forum... http://demigodllc.com/articles/6.5-shootout-260-6.5x47-6.5-creedmoor/
Also the 260 has a smoother angle on the shoulder that is great news for autoloading firearms an in line with military service cartridges following
the same dimensions directives (ie: 5.45x39, 5.56/223R, 7.62x51/308W, 338LM). This is huge for a cartridge to have a chance to be considered
for service use.

What OAL do you run on your .260 loads, and how far off the lands are you?

Edit: I didn't see where the article you linked mentioned what OAL the .260's were loaded to. The only time I saw OAL mentioned was when he brought up the shorter OAL of the 6.5x47 as an upside for seating bullets out a bit so that the bearing surface was above the case mouth. If the "typical magazines" you mentioned are AICS type mags, then yes, many of that pattern will allow up to 2.88" OAL with no problems. That's well over SAAMI OAL for the .260, but with longer mag rifles like the AICS, one should not have problems.

 

[Offfhand]

Lots of military team members gave their match brass to civilians; they paid for it in taxes. I always cautioned those getting mine that they were not all that great for competition but good for other stuff. None of the military semiauto match conditioned rifles had their bolt faces squared up with chamber axes. Those case's heads were flattened out of square and if reloaded, would string shots in the 1 to 7 o'clock axis right angles to the bolt locking lug in-battery axis. Stringing typically added 1/3 to 2/3 MOA to groups new cases produced. New case heads are typically quite square to their long axis.

What Bart is saying about out-of-square case heads is worth paying attention to. If you want to be pickey it applies to new brass as well. Back in the '80's or therebouts several high-power shooters, myself included, carried it to the n'th degree and even turned the heads on new brass enough to level off the high spots. A guy I occasionally shot with by the name of Clayton Audette was a big experimenter and tinkerer and gave me a gadget he made for measuring head squareness and other dimensions. After a couple years I decided turning heads wasn't worth the bother and gave it up but still have some turned head ammo left over from Perry years ago, as shown in attached photo. Here's also photos Audett's case measuring gadget, with shot of it rigged for measuring head squareness.

 

[Bart B.]

I takled with Creighton Audette in the 1960's about his tests. He said to just slide the case head into a small T square then watch the mouth spin around in circles.

Or use a Wilson case trimmer case holder clamped vertically in a vise, drop a case down into it, then lay a small bubble level on the case head in different orientations. If the bubble always pointed the same direction from the case head, that case head was square. He suggested using a perfectly square case headed case to orient the case holder vertical in the vise, then just drop in a case, cap it with the bubble and see if the bubble was centered on the little round level.

If your bolt face is properly squared up after its lugs are lapped to full contact, note new cases will have pretty square heads to start with, but very square after their first firing. They'll stay square through dozes of reloads if properly resized and fired in that same rifle; or another whose bolt face and lugs are also trued up.

 

[1stmarine]

Yes, Accuracy International magazines are pretty much the standard but there some other models that give even a tad more.
Original SAAMI dimensions and reamers are less than ideal for this kind of use and folks do not use the typical light hunting commercial rifles or barrels/twist for long range anyway.
But there are some very good ones and more showing up starting with the affordable savage predator hunter and also the Long Range Precision Magazine.
For long range the 260 OAL is 2.865 for the longest bullets like the berger 140gr VLD. and 2.810 for the berger 130gr hybrid that work in AR magazines like DPMS and PMAG, if someone is going to use that for whatever.
Because of the extra capacity these get the fastest speed out of a 6.5mm in 308 type magazine although that is not the main benefit, the smooth shoulder angle is, specially for auto-loaders / tactical use.

 

[Bart B.]

Original SAAMI dimensions and reamers are less than ideal for this kind of use

Why not?

My match rifle chambers' are SAAMI spec except for a shorter freebore in .308 Win Palma rifles for 155-gr. bullets only. Both new and full length sized fired cases center perfectly in them when fired.

The MIL SPEC 7.62 NATO chambers in the Garands I shot perfectly centered new Arsenal and commercial match ammo cases good enough to test 2/3rds MOA at 600 yards.

Doesn't matter if the case head is .001" or .002" off center at the back end of the chamber when fired.

 

[1stmarine]

Why not?

Bart,
You are right. One could work with the SAAMI chamber and 1:8 twist barrels.
I was thinking more in line wiht the 2.8" limitation for tactical use / long range where in practical terms this is not a realistic limitation.
That is why most people considering long range are looking at the bullets first and then finding the chamber/reamer, magazine systems that better suites that use
withing the constrains of the modern tactical rifle and not some other outdated constrains.