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.260 or 6.5 Creed....Vote AR 10 build

I vote 6.5 Creedmoor. My Seekins SP-10 in 6.5 Creedmoor shoots factory Hornady extremely well in case I don't have time to handload. Factory 6.5 Creedmoor is generally available in comparison to 260 ammo.

Phil G
 
And the 6.5 has greater port erosion over time in gas guns. Pick your poison.

As for me, I have both. But tonight my vote is .260 ?
Not saying you are wrong, but you'll have to explain that one to me. Can't imagine how the port is going to know the difference between the two. Bullet weight, powder charge, and bore are identical. I could see powder making a difference, but that's not a 260 vs creed thing.
 
If a cartridge designer were to sit down today to build a 6.5 cartridge for a 2.8” magazine, would the result look like a .260, or a creedmoor?

Creedmoor is the obvious choice if you aren’t tooled up and supplied for .260 already.
 
Not saying you are wrong, but you'll have to explain that one to me. Can't imagine how the port is going to know the difference between the two. Bullet weight, powder charge, and bore are identical. I could see powder making a difference, but that's not a 260 vs creed thing.

The science is out their on the CM. Not debating that at all. But it came to my attention recently after a manufacturer submitted a white paper on it to the DOD, during their selection of either .260 or CM. It would seem the straight walls of the case and where the pressure curve is happening is causing erosion that can cause reliability issues sooner than that of the .260. Like I said, pick your poison or do what I did and get both. =)
 
I shoot 260’s in Bolts and have a LMT 308. If I were building one, it would be 6.5 CM hands down. Auto’s are rougher on brass and I would be wearing reloading classifieds out buying 1x fired quality brass. That would be the main reason and I think a very economic one.
 
The science is out their on the CM. Not debating that at all. But it came to my attention recently after a manufacturer submitted a white paper on it to the DOD, during their selection of either .260 or CM. It would seem the straight walls of the case and where the pressure curve is happening is causing erosion that can cause reliability issues sooner than that of the .260. Like I said, pick your poison or do what I did and get both. =)

So, did Mark put out a paper on this? I know he posted it on ARF, but didn’t provide any substantiation other than “this is what I’ve seen”, and I don’t care if others have seen this mentality.

I’d think that him selling a complete 260 and not a complete 6.5 creedmoor plays more of a factor in what he pushes than the case wall shape.
 
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Coming from a die hard .260 shooter who shot one years ago, and never shot or owned a 6.5 CM......6.5 CM everytime in a semi-auto platform. The 6.5 was built around the high BC bullets at mag length. I shoot an AI AT that uses AW mags. I also reload. I would go 260 only because I am not hindered by a typical mag length, and the 260 benefits somewhat as Lowlight said in the video above. I would even recommend 6.5 CM to a new shooter. Lowlight hit every single point. New to shooting and semi-auto: 6.5 CM. Experienced reloader moving from 308 and not limited to mag length: .260
 
I'm pretty sure you have a lot more barrel choices with 6.5 Creedmoor, brass is available from many sources, new bullets are being designed around magazine length in 6.5 Creedmoor, many flavors of box ammo (which generally work well in ARs), there are lots of practical reasons for 6.5 Creedmoor.

I think it's a much tougher decision to pick between .243, 6*47 Lapua and 6 Creedmoor...
 
I’m very happy with my Creedmoor..

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Versatile cartridge for the platform. Does well with the factory Hornady 140, 147’s and FGMM 130’s, although the FGMM is hot. Also does well with the 142SMK.

Results from the range over the past few months.

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Don't get me wrong, I love 6.5 CM, but in the gas gun, I run .260. I run Winchester .243 brass and don't care a bit when I lose it or it gets dented during extraction.
 
guys,
The 260 is a better all round cartridge by far.
And all this talk about brass,the 260 has to be the easy alternative.I have had a 260 for over 15 years and if I have ever been short on brass just used 243 brass simply necked up.It chambers and shoots perfectly with no loss in performance.
 
And if the answers is “I’m building it myself”, chances are you’ll be learning a whole bunch about the timing of gas guns, the amount of bullshit advice that lives online, and ending up with a rifle that is setup with a few different parts than you started with.

Buy whatever floats your boat, and fits what you need the rifle to do. The AR10 works best when the purpose is defined, then the tool chosen.
 
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Creed. Gasser’s are different animals than bolt guns. Shoot it and leave the brass or pick it for scrap, buy another case and enjoy. Run a 260 in your bolt gun, reload it, and enjoy the slight performance increase.
 
So, did Mark put out a paper on this? I know he posted it on ARF, but didn’t provide any substantiation other than “this is what I’ve seen”, and I don’t care if others have seen this mentality.

I’d think that him selling a complete 260 and not a complete 6.5 creedmoor plays more of a factor in what he pushes than the case wall shape.

Yea i read that too... And have a LaRue .260 barrel and a LaRue 6.5 barrel for my LaRue PreditOBR and they where Both over gassed as hell... But the .260 more so causing malfunctions... (with FGMM and Hornaday ELD ) there is like a 60 page thread with other people saying the same thing... which is the kind of the opposite of what he said in that one post we are talking about.. I called the shop they blamed it on the can I was using.. it was still over gassed with out the can... I ran s stiffer spring and buffer.. I got one of there cans for $400 but have not had the time or motivations to go out and test it some more... I kind of feel like there Guinea pig....

My vote 6.5 Creed.. more ammo and cheaper i don't reload or plan on it...


Berger match is working on a load with there AR Hybrid 130gr load.. could be interesting if it was tested for a auto and not a bolt gun..
 
I have multiple 6.5 Creedmoors and 260 Remingtons in AR format. When you configure the rifles properly, there is no appreciable difference between the two cartridges in an AR platform as case capacity when limited to 2.820" OAL to fit magazine is for all practical purposes the same.

IMHO, gas guns are better served with more conventional ogive profile match bullets as it matches the feed geometry / relationships between magazine, feed ramps and chamber. VLDs / hybrids (Berger AR hybrid is exception as it is not a long ogive profile like the Berger hybrids) are not my first choice in a gas gun, creates more issues then it solves. 120 Scenar-L, 120 SMK, 120 Berger Match BT, 130 Norma, 130 Berger AR hybrid, 136 Scenar-L, 139 Scenar, 140 SMK, 142 SMK or similar bullet with 9-11, maybe 12 caliber ogive will feed better with less meplat / tip deformation than will the longer ogive VLD and hybrid bullets.

Port location, port size, dwell time (amount of barrel after port), buffer weight, spring K, trigger used and running only suppressed / only unsuppressed or both suppressed / unsuppressed will have pretty large impact on how rifle behaves / should be set up.

Do it all rifle, 20" barrel with a +2 gas system would be a pretty handy overall package.

I prefer 260 over the 6.5 Creed in general. 260 feeds a little smoother. Gas gun or bolt gun, the more gradual shoulder angle and slightly more body taper lends itself to smoother feeding. Bolt rifle where you can put bullet where you want it, 260 all the way. I've done several 260s over the years in actions / magazine systems where I could load long (over 3" OAL) and that really allowed the 260 to shine, pull away from the 6.5 Creed.

I can not really vote for one over the other in a gas gun as if both are configured properly, there will be next to no difference or so little as to be none.

Get the one that makes it better between YOUR ears. There isn't enough difference between a 260 and a 6.5 Creed to fret over when constrained to 2.820" max OAL to fit in AR magazine.