Ive got a Ruger No.1V in 22-250 that has as far as I can figure appox .006 NXS headspace.If I load with the bullet into the lands I have no problems but if not seated into the lands then I get primer setback and smokey cases. My question is why doesnt the case fireform into the proper shape when firing with the bullet seated to touch the lands? I only neck size so I know Im not setting the shoulder back. Thanks to all.
Multi Vis.

Hey Multi Viz, Your "Load" may not be strong enough to cause the case to expand and fill the chamber.

What Load are you actually using?

Do you have access to a set of 0.0001" capable Micrometers? (Not 0.001" capable Calipers, they aren't accurate enough.)

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Good hunting and clean 1-shot kills, Hot Core

Hot Core Im shooting 35gr.4064 - which is not a light load. And yes I can measure less than .001. Multi Vis

Multivis, I expect that the answer lies in the fact that a load with the bullet into the lands generates more pressure (in particular, a quicker rise on the pressure curve) than the same load with the bullet backed off a little.

What weight bullet are you shooting?

There is nothing wrong with continuing to load into the lands, if the accuracy is there.

Another option is to go to a faster powder, which will make the soot go away, too. 4895 comes to mind, or Benchmark. HTH, Dutch.

Im shooting 55gr.bullets,any lighter and they are not long enough to seat into the lands. Ive tried 748,Varget,H-380,RL-15,H-380,4320 and 4064 all with the same result.
Still seems to me that when fired with the bullet seated into the lands that the case would fireform to the true chamber size if there is nxs headspace. Multi Vis.

I agree, the case should fireform to the chamber.

I would check the adjustment on the neck sizing die. Actually, most of them will "kiss" the shoulder if adjusted all the way down. Therefore, you could be setting the shoulder back to "factory" when you neck size.

I only neck size half the neck when sizing so I dont think thats it. I was just out at the bench messing around since its to windy and cold to go to the range and measured some other 22-250 brass that Ive been shooting in a bolt gun and the datum line on its shoulder is .004 longer than the ones Ive shot in the No.1,so maybe Ive been dealing with bad brass all along. I assumed and we know what that means!!!!! Have loaded up some in the other brass and will see what happens when weather permits. Multi Vis