Excessive?

[JFrank]

Yuh
Actually I I'm seeing .007 neck clearance on a SAMMI chamber being common
The extra .004 is being created by the reloader sizing down for Bullet hold.
I'm I screwed up AGAIN?

 

[Uncle Ed]

In a off the shelf factory rifle you have no control over how how much the neck expands when fired.

And using a bushing die to reduce the neck diameter this much can induce neck runout.

And if Jack O'Connor was here he would tell the OP his .270 Winchester is the worlds best non-belted magnum.