Home Forums Hunting & Shooting Ask The Gunwriters Why/How does the Creedmoor out run the 260 & 6.5x55?

The 260 has 2-3 grains more capacity and the 6.5x55 around five but I see loads for the Creedmoor that are faster than either. Is this due to the mythical cartridge efficiency or over optimistic reloading? According to JBs one quarter rule the 260 & 6.5x55 should get at least 30 to 60 fps more than the Creedmoor.

pressure

The Creedmoor doesn't run faster, guys here just seem to load it pretty hot.

As Bugger said, "pressure"... but, of course, the 6.5x55 data is pretty light on account of all the old rifles chambered for it.

Agree....I don't think I have seen many claim the 6.5 CM is capable of velocities faster than the 260 or 6.5X55 when all are being loaded to a similar fashion. The latter to cartridges should always out run the 6.5 CM as like you said they have more room for more powder.

.260 SAAMI max - 60k psi
6.5x55 SAAMI max - 51k psi
6.5 Creedmoor SAAMI max - 62k psi

i wonder what the pressure sweet spot is for accuracy with modern cartridges with the 30 degree shoulder... I suppose other variables come in to play (bore diameter, bullet construction, twist to name a few) and it all forms a trade space...

300 RUM is 65K, same for 300 RSAUM...

I load my Swede to 59k PSI and I can sling 140 gr bullets at 2950 FPS using RL26. I don't think I've seen a Creedmoor do that staying within the same pressure range.

Load the 6.5x55 to 62k in Tikka, Sako, or any other strong action, and it will be faster. But, it's been killing so well, and so accurate for so many years, why bother?

It doesn't out run them, but 30 to 60 FPS means diddly squat.

I'll and another one, 6.5X57 Mauser, basically a 7X57 necked down. It's a pressure thing. In a modern rifle the 6.5X55 and 6.5X57 will do what the Creedmoor can do. If one goes beyond 130g bullets then the 6.5X55 and 6.5X57 will exceed what the Creedmoor can do. Velocity always seems to be the question, I like accuracy. The 6.5 Creedmoor is accurate, but so are the 6.5X55 and 6.5X57. Of course neither the 6.5X55 or 6.5X57 can have the "magical" short action..

Yes all true and I do think there is something to cartridge efficiency but not sure what it is. One article I read showed that there was no difference in velocity between different neck configurations but they stopped short on testing pressure/velocity uniformity which things do seem to indicate certain designs contribute to more uniformity. Look at the PPCs and other short-fat rounds and with a 30 degree necks there does seem to be an improvement in uniformity.

Also accuracy nodes or windows seem to run across the board in spite of which cartridge it is fired from. Certain bullets esp. VLD types will run best at say 2900 fps and it does not matter which case they are shot out of even if that case could go to 3,200 fps.

I wish I had accurate strain or pressure equipment. If I did I bet the 101 year old Swede at 65,000 psi could give the .264 Winchester a reason to look over it's shoulder to see what was breathing down it's neck.

This reminds me of a test PO Ackley did with I think the 260 AAR on the 7x57 case, the 6.5-06 and a magnum .264. He ran crazy high pressures by working up loads till they blew a primer and then backing off one grain of powder. Must have been in the 70,000 psi range but still interesting information. Between the three there was less than 300 fps difference if I recall correctly.

Layne Simpson wrote that it takes at least 300 fps difference to see any performance difference in hunting use. I would tend to agree but experience tells me that even 300 fps may be undetectable in actual field applications. I better not go further in this line of thought or I will have to empty my gun safes and only reserve two or three due to practicality.

the Creed is magic, haven't you heard?

-Jake

Mule Deers answer from another post covers it pretty much. "In some of the 6.5 Creedmoor/6.5 Swede threads the posters are FOS--on both sides."

How long is the barrel on your Swede? What is the make of your rifle?


2950 FPS with 140 grainers is very impressive.

Because of the terrain I hunt, extra velocity is of little benefit to me. I generally pick a bullet and a powder that gives usable speed at the low end, then quit when I get good groups. Sometimes that's right at the beginning, as in 46gr of H4895 with 150gr NPs in the .30/06.

A ballistic app like the one Nosler has makes it easy to see the effect additional velocity has on trajectory (and energy). Takes a good bit of speed to make much practical difference at short to medium range. Guys who shoot way out there want all they can get, of course. Another benefit is that you can see how far out the bullet you're using will expand, according to manufacturer specs anyway.

Equal pressure, the Creed comes in last.

New powders, such as RL-26, give new life to the Swede in a strong action.

To me, the CM is the best SA round. I like mine.

Also, seems to me the CM is easier to load for, not finicky about loads, shoots almost anything well.

My Swede is a tack driver with select loads,; my CM is inch or less with most any loads, even various factory ammo, probably the easiest to load for rifle I have and that includes some good ones..

DF

Could you list specific bullets or point me to your source info? Not wanting to bust your stones, but genuinely curious. The 6.5 bug may bite me before long.

Thanks,


Okie John

Prezactly.

There about a 5-grain difference in powder room between the Creedmoor and the 6.5x55, around 10%, with the .260 in between. This translates to about a 2.5% difference in potential velocity when both the the 6.5 Creedmoor and 6.5x55 are loaded to the same pressures, 75 fps in loads around 3000 fps and less with bullets at lower velocities.