260/6.5mm Creedmoor

[Grimstod]

Question: 1 for debate or just plain illumination.

260 and 6.5 creedmoor have same performance even though 260 is a bigger case. Does the creedmore have an advantage in accuracy because of its efficancy?

Question: 2
Lapua makes 260 brass but not Creed more. Can you form 260 into 6.5creedmore?

 

[deepwater]

Norma & Nosler make 6.5 Creedmoor brass.

deepwater

 

[Laurie]

There is not a great difference in their respective case capacities. In my rifles' chambers, fired Hornady Creedmoor brass holds 53.2gn water whilst my 260's chamber and brass produce 54.4 to 56.5gn depending on case make.

While the 260 retained its parent 308 Win's SAAMI MAP of 60,191 psi, Hornady developed the Creedmoor to allow higher pressures of around 63,000 psi. On top of that, the Creedmoor's shorter, fatter case sees any given bullet seated to their common COAL of 2.800" intrude a shorter distance into the case. When you start talking 140s, the 260 needs them seated pretty deep reducing the available combustion chamber volume. Taking my rifles and seating the 142gn Sierra MK to the standard 2.800 COAL, the Creedmoor has a usable case capacity of 3.045 cc whilst the 260 Rem using Lapua brass and the same bullet / COAL is only marginally more at 3.068cc, ~ +0.75% - negligible in real life.

Norma 6.5 Creedmoor brass may be thinner than Hornady's on the basis of experience with similar cartridges and could therefore have a usable capacity that matches or slightly exceeds that of some 260 Rem brass. On the other hand feeding my 260 with Remington brass would give it a rather larger edge as it's thin and 'roomy' compared to Lapua - not that too many people of this forum feed their 260s with Remington cases.

Personally, I reckon the Creedmoor the better design losing out only on the relatively poor choice of brass, but I'm sure that'll change over time.

If you hunt around on this forum you'll find discussions on reforming other cases to 6.5 Creedmoor. I think that .22-250 is the first choice although the finished article is left a little short of the Creedmoor's trim-to length. If you do a search for posts by FJIM on this forum, he's reformed Lapua 'Palma' (small primer) brass to Creedmoor and got some impressive velocities from a 24-inch barrel using this very strong brass.

 

[Grimstod]

Isn't 260 the same thing as 308 Palma just necked down to 6.5mm? If they can form Creedmoor brass with Palma could it not be done with 260 a little easier?

 

[Laurie]

Isn't 260 the same thing as 308 Palma just necked down to 6.5mm? If they can form Creedmoor brass with Palma could it not be done with 260 a little easier?

Of course - but it doesn't change the case length / COAL / bullet seating relationship issues. As the pair (and the smaller but significantly higher pressure 6.5X47L) give very similar real world velocities and all three are capable of extreme accuracy in the right rifle, choice comes down to personal preference, availability / price / longevity of brass and other suchlike relatively marginal factors.

The 260 does have the advantage of being capable of benefitting from Ackleyising - a 40-deg shoulder Ackley form chamber does give a useful boost to the cartridge and was (still is?) popular in some sniper and tactical disciplines. For mid and long range prone slowfire disciplines, a single shot rifle can be throated to accept longer OAL cartridges overcoming most or all of the deep seating issue.

The 260 has had the benefit of being around much longer than the other two and after a slow start what was originally a light deer and metallic silhouettes cartridge has created a fair sized niche in the target shooting world. The Creedmoor got off to a faster start, although it's barely known outside of the US ..... so far!

 

[swampthang]

i shoot the 6.5 creedmoor as my leight gun in 1000 yd i.b.s. and it consistanly shoot sub 5 in 5 shot groups with a 140 berger vld.
i think the shoulder angle burns powder more effeciantly , while 2 gr lighter case capacity than a 260 the creedmoor really shoots well at 1000 yards.
the only thing i wish is that there were better brass offerings- nosler is the best offering as of yet but you have to finance them.
you can make creedmoor brass out of lapua 308 but i havent went down that road, instead i buy several hundred same lot hornady brass and sort through them till i get enough to shoot the ibs season.
as a general rule metric calibers havent taken off in the us but i see the creedmoor being here to stay- you just cant overlook how well it performs.