NOSLER 6.5mm Custom Comp Problem

[Barklee77]

I have been having problems with my savage 12 f class 6.5x284n. I have only used nosler cases and bullets and h4350 and h4831sc. I shot 50 rounds of each powder and noticed some shots seemed to be key-holing. I spoke to a gunsmith and he said that other people shooting the same rifle have been having problems with the same bullet. Nosler 6.5mm 140gr CC. He asked me to bring some bullets from the same box and I also brought some lapua senar 139gr and smk 142gr. He took the micro meter and measured right above the boat tail and all the noslers measured .263850 or less. The lapua and smk measured .26405 no less.

I was shocked, he said that this can cause the instability of the bullets if they are smaller than the barrel by a few thousands.

Is this true? Are there any one who have seen this problem?

Next week I will shoot some Corbon lapua factory cartridges
and see if it is the bullets causing the key-holing.

On a side note the same gunsmith told me that in the last few months he has seen factory rifles that do not have the rifling all the way to the end of the barrel.

 

[Joe S]

Don`t buy that.
I have used the 140 gr Nosler CC in my 6.5x55 and a 260 Rem had no problems with stability I could tell. The Swede has a Hart 1/8 twist and velocity ~2650 fps, the 260 is a bone stock Kimber M84, 1/9 twist @ 2700 fps.

 

[Octopus]

If your velocity is low the bullet RPM will be low. This can make it less stable.

What is your barrel twist?

What is your bullet muzzle velocity.

Also, sometimes a bad crown on the muzzle can add to the wobble on a boat tail bullet when it exits the muzzle. Easy to check. If it bad you may be able to see it the edge with the bore scope or a mag glass.

 

[TedH]

I haven't measured any of those bullets but if they are undersized then it could cause some issues if your bore is oversized. SAMMI specs are a plus or minus deal. So your bore could be bigger than the bore on another gun but still be in spec. But that difference will only be about .0025 or less.
I measure bullets all the time and some bullets are fat and others are thin. They are generally thin when the die is new and fat when the die gets older. The amount of lube used when the bullet is swaged can affect the diameter as well.
I also measure bores and some are loose and some are tight.
But their are other things that can cause similar issues. Velocity could be one thing.
Just shoot some match kings or another brand and see if you get the same issue.
If the gun shoots fine with another bullet then just avoid those.
Ted