6.5 creedmoor vs 6.5x47 velocities

[Flyingbullseye]

First off this is not a thread about which cartridge is better or help in choosing one over the other. Not wanting to ask a stupid question but still trying to learn the in's and out's of what does what.

If I am correct the dimensions between the two is 1mm in length, the creedmoor being the longer of the two. Shooting the same gr round and everything else being equal why is the lapua round give or take 150fps slower despite having a higher pressure? Wouldn't the extra pressure make up for the slightly smaller case capacity? Also, why is the creedmoor very close or nearly the same velocity as the .260 despite being 3mm shorter?

Haven't started handloading yet (dies still in the mail) and I don't have any experience with any 6.5 round but was curious how the different dimensions had the creedmoor round closer in performance to the .260 while its dimensions were much closer to the lapua round.

Flyingbullseye

 

[nhassey48]

Re: 6.5 creedmoor vs 6.5x47 velocities

The 6.5 CM is slightly fatter which is why is has more case capacity, hence the velocity difference. The velocity of the creedmoor is actually not more than a 260 when you use the same rifle specs. You can pretty much assume a 28" 6.5 creedmoor is equal to a 26" .260. The creedmoor from what I understood was designed to have about 260 ballistics without having feeding issues that the .260 COULD have when loaded with long bullets. They say to that the shorter, fatter cartridges have a more consistant burn rate. With a 6.5 CM, you can load to the lands and have no problems in 308 sized magazines.

You have to think also, 1mm taller when you find the volume of the case, is quiet a bit more powder which is why it is higher than a 6.5x47.

 

[buffybuster]

Re: 6.5 creedmoor vs 6.5x47 velocities

They both share the same bolt face (0.473") and have essentially the same shoulder diameter, so one is not fatter than the other but the Creedmoor is slightly longer to the shoulder and has the capacity advantage, though the Lapua can run at higher pressures. Real world velocities are probably a wash. As for published velocities you have to be careful that barrel lengths are equal. I believe Hornady's published Creedmoor velocities are from a 28" barrel, which is not the typical tactical rifle barrel length.

 

[nhassey48]

Re: 6.5 creedmoor vs 6.5x47 velocities

Yea, the creedmoor is fatter than the .260, and is taller than the 6.5x47.