Good SDs but horrible accuracy?

[Corse]

I have been trying to get some Nosler 70gr RDFs to shoot and I tried some 748 today with both the RDF and 69 TMK.
The RDF had some decent SDs (8.8) but absolutely horrible groups, I didn’t measure, but 5” would be generous. The TMK had a SD of 1 for two separate charge weights and the third was 0, but similar groups to the RDF.
I shot a control group with 52gr MK and it was typical of the gun @ 0.4”.

Has anyone experienced anything like this before?

[gaijin]

What were they shot from, barrel twist?

[Corse]

It was a stainless 18” proof research 1\8 twist.

[gaijin]

Assume no sign of yawing/destabilizing? The 1/8 should be just fine with heavier bullets you listed.

And no, I’ve never experienced that.

[Corse]

They were stabilized. I’ve never had SDs that good, but I have also never seen accuracy that bad.

[Nightvisionary]

Low Standard Deviation as a general rule is a good measure and goal but it is not the end all in reloading accurate ammunition. Over the years I have had mediocre accuracy from low SD loads and excellent accuracy with SD's in the 20's. There are enough variables in the process that a single factor may or may not contribute to overall consistency.

[Bimmer]

The TMK had a SD of 1 for two separate charge weights and the third was 0...

Really, SDs of 0-1? I'm impressed... almost incredulous.

Throwing stuff at the wall: Given that the rifle and the bullets aren't the issue, maybe your charge weight is too high/low? Or your seating depth is off?

[Corse]

Really, SDs of 0-1? I'm impressed... almost incredulous.

Throwing stuff at the wall: Given that the rifle and the bullets aren't the issue, maybe your charge weight is too high/low? Or your seating depth is off?

I could hardly believe the SDs either, that’s why I’m so disappointed in the accuracy, I was hoping for a great long range combo.

Not much room with the seating depth, set at max mag length. The charge weight could be adjusted, it is about .5gr under max.

[Bimmer]

The charge weight could be adjusted, it is about .5gr under max.

Sounds like there's your answer...

[Corse]

I would like to think that is it, but even if the groups ended up at half the size, which I doubt, they would still be worthless. This whole thing is perplexing.