6XC vs the 6x47 Lapua

[TheSwede]

Until now I've only owned 6mm barrels chambered for the tried and trusted 6BR. No complaints with that fine cartridge. Though now I've been looking for a 6mm cartridge that could drive the heavier bullets faster and work more right down in a unmodded magazine. Now it most likely stands between the 6XC and the 6x47 Lapua.
Now give me the pros and cons on the two!
Is the Lapua to much mess around before getting the cartridge good to go,downsize, neckturning etc)? Is the lapua brass so much superior to the norma? Is the smaller primer such a big advantage?
Is one cartridge easier to tune over another?
What do you think? Whats your experience? Have you tried both? Just one of them? Shot 1000y benchrest or 300y from a sling? Just observations or opinions?
If you have some thing to say, anything, theoretically or from the practical write it down here!
Which should i choose?

 

[Asa_Yam]

Which should i choose?

Flip a coin - both cartridges are essentially the same, in terms of volume and velocity. Either one is accurate - I've seen good 1000 yard prone scores,high 190s/200s) turned in using both cartridges.

Don't let the the "superiority" of Lapua brass sway your decision. Lapua makes "bad" brass every now and then - "soft" .308 cases have recently,~3 months ago) been reported. There are multiple,reliable) reports of 6.5x47 Lapua brass with burrs on the flash hole - not typical for other Lapua cases. The "small primer advantage" of the 6x47 case is probably a myth as well - at least one report of achieving similar accuracy by lowering muzzle velocity to that delivered by a small primered case exists.

FACT: In 300 meter position shooting,the distance for which the parent 6.5x47 case was developed), the 6XC has won more matches. For position shooting, any theoretical advantages are just that - theoretical. The shooter matters far more, and has a far larger influence on the final outcome.

For the record, I occasionally shoot a 6XC. Had the 6x47 been available when the rifle was originally chambered, it wouldn't have been a bad choice.

 

[TheSwede]

Interesting that you mention the small primer as a myth. What would you say that the myth consist of, and what would be closer to the truth?
Anyone that can give some testimony on comparing between the XC norma brass and x47 lapua brass? I've read reports of the primer pockets of the XC norma brass becoming lose pretty fast.

 

[Asa_Yam]

Interesting that you mention the small primer as a myth. What would you say that the myth consist of, and what would be closer to the truth?

http://www.websitetoolbox.com/tool/post/6mmbr/show_single_post?pid=12162513&postcount=11

David Tubb,inventor of the 6XC) posted the above. However, the person who ran the test was the late Martin Hull - former Chief Ballistician at Sierra Bullets.

 

[TheSwede]

I can understand the results in the link. But isn't the thing about small rifle pocket related to the ability to handle high pressures better because of the added material in the base? Or?

 

[Asa_Yam]

There's more to the strength of a casing than just the metal in the head surrounding the primer. Case web thickness, and brass composition/hardness/work hardening all have an effect. Get stupid with pressure, and primers will blow in any casing. Large primer, small primer, it doesn't matter beyond that magic point.

Here's why maximum velocity doesn't matter as much as you think:

- Gains in MV with significant pressure changes are often minor. A 7000 PSI increase in chamber may yield less than 100 FPS.,Not "real world" data, but probably close to it.)

- Downrange exterior ballistics,drop and drift) may not be that great even with 100 FPS more MV. For example, the faster round might drift 1/2 MOA less in a 10 MPH crosswind. At 2 MPH,about the limit that most people can read changes in the wind), we're looking at 0.04 MOA less drift. Even for most LR benchrest shooters this is insignificant, as they tend to "machine gun" rounds in one condition in an attempt to shoot in a UNIFORM wind condition.

- Barrel wear typically accelerates with greater velocity. With MVs around 3000 FPS, both calibers deliver ~2500 rounds of accurate shooting. Increase pressure, and odds are that number drops.

- At near-maximum pressures, accuracy can and does decrease. Bullet bases can deform under pressure, and high pressure gas blow-by as the bullet leaves the barrel can "tip" the projectile. Both result in increased dispersion.

Performance of most heavy 6mm bullets around 3000 FPS is pretty good. Accuracy at higher velocities is possible, but pressures skyrocket unless you use really slow powders. The jury is out on the latter - one LR prone shooter has had good results using Reloder 17, but another equally accomplished shooter,shoots both prone and LR benchrest) has threatened to use his supply of RE-17,same lot) for fertilizer because it won't deliver acceptable accuracy.

Seriously, if you seek greater velocity, it is probably cheaper, easier, and safer to use a case with more capacity. The .243 Winchester or 6mm Remington come to mind.