6.5 Creedmore AR barrel preference

[deemus]

What length barrel are you guys using?

I see various lengths, but was hoping to not replicate all the research I'm sure a bunch of you have already done. I am considering an upper for a lower I built a while back, and was curious if there is a concensus on barrel length and bullet weight for a particular barrel length.

Kind of like the 168g bullet is the go-to for 308. What is the go-to (if there is one) for the 6.5 Creedmore?

Thanks in advance for sharing your experience with this round. I don't even know anyone that has one, so I am starting from scratch.

 

[Charlie]

Subscribed to learn!

 

[robertc1024]

Paging SouthTXPilot - he had/has one he built on an AR platform that was a tack driver.

 

[jrbfishn]

Kind of interested myself.

Sent from my SAMSUNG-SM-G870A using Tapatalk

 

[deemus]

Found this article. Lots of good info here.

http://www.range365.com/65-creedmoor-long-range-king#page-10

 

[ed308]

I plan to convert my .308 AR10 to a 6.5 Creedmoor. What length should you go with? You'll need to answer that question for yourself. Selecting a barrel length depends on the rifles intended application. A hunter's needs will differ from a competitive precision shooter. Velocity and drift benefit from a longer barrel and with lighter bullets at longer ranges. But as the bullet weight increases, that's less apparent. A 24″ barrel would be a good compromise for a 27" barrel. But when dropping down to 22", you still don't loose all that much compared to a 27" barrel. And if shooting at a range under 600 yards or less, you could drop down even shorter to 16-18" barrels. But shorter barrels do vibrate or whip more that a longer barrel.

22" for my AR10. But I'd go 24" or longer on a bolt rifle.

 

[sucker76]

Well I have thought about this topic too. I have read on other forums that you shouldn't go below 22" because you leave too much on the table in the way of velocity. I liked the idea of a shorter, handier AR and wanted a 18" barrel. I already have a 6.5CM with 26" and 22" barrel and now I'll have a 18" one too. The barrel still hasn't come in so no load development yet.

 

[Younggun]

Interesting thought on the vibration. I remember reading the opposite in an article and I think I saw it mentioned today while reading on the Krieger barrels website that longer barrels are more prone to suffer from harmonics.

I'll try to find it again but I'd be interested in reading what you've found relating to shorter barrels.

 

[sucker76]

I also remember that shorter barrels are less prone to whip...

 

[Younggun]

Here's an article from Truth About Guns that was shared here a while back.

http://www.thetruthaboutguns.com/20...t-barrel-length-muzzle-velocity-and-accuracy/

 

[Dawico]

I have a 24" barrel because that is what Savage put on it.

STP swapped from a 20" to a 24" barrel on his AR. He also stepped up in quality so the length was only a small piece of the puzzle.

 

[deemus]

Here's an article from Truth About Guns that was shared here a while back.

http://www.thetruthaboutguns.com/20...t-barrel-length-muzzle-velocity-and-accuracy/

Good article.

 

[Texas42]

For a hunting gun, I see no reason for longer than an 18".

But that's just me. I dont shoot animals at >300 yards.

 

[sucker76]

I just got the barrel in and here it is mocked up on the receiver. 18" Ballistic Advantage barrel and 15.5" Odin Works handguard.

Any kind of shooting data will be a long way out. Work, hurricane cleanup and range under water are getting in the way.

 

[benenglish]

...shorter barrels do vibrate or whip more that a longer barrel.

...I think I saw it mentioned...that longer barrels are more prone to suffer from harmonics.

I also remember that shorter barrels are less prone to whip...

Executive summary:
All else being equal, pistols are more accurate than rifles because pistols have shorter barrels.

Long version:
I shouldn't bother with the long version because I've written it up, on TGT and elsewhere, far too many times already. However, there may be new folks around. For them, here's a short version of the long version.

Let someone with a long history of IHMSA or other long-range pistol shooting bend your ear on this one. XP pistols with run-of-the-mill Remington (read: pretty crappy) barrels in 7BR were routinely half-MOA guns, out of the box, decades ago. Those were the days when half-MOA rifles would make the cover of gun mags on account of their fantastic accuracy.

Think of it this way: Skinny barrels whip more than thick ones, right? That's bad, right? So if we define "skinny" by the ratio of cross-sectional diameter to length, any barrel can be made twice as thick by simply shortening the length by half.

Demonstrate it to yourself. Take a stick of wood and bend it in your hands. Note how many inches you can move one end while holding the other end stationary. Now saw that stick in half and bend it again. Applying the same force to the shortened stick will NOT move one end, relative to the other, as much as when the stick was longer.

Again, with all else being equal, shorter == stiffer == more accurate.

The article referenced up-thread clearly says

...the shortest barrel length provided the most consistent accuracy across the board and the longest length proved to be the least accurate with the same loads

Unlimited-class pistol silhouette shooters, who get their giggles from embarrassing rifle shooters, have understood this since the 1970s. It's amazing to me that some people still don't get it. There are still some folks with decades of shooting experience who insist that longer barrels are more accurate.

These people can rightly be dismissed as ineducable.