What has been your experience when fireforming cases to .22 K Hornet ?
Have found that during fireforming my standard Hornet load has gone from about 1 inch groups to about 2 1/4 .No good for anything but practise .
Still waiting for dies so haven't tried any formed cases but it needs to get a whole lot better or this one's going down the road .

nothing to it - just stick your hornet round in the chamber and fire it. Very little case loss, & the bullet will probably actually hit pretty close to what you're aiming at.

I have virtually as good accuracy with fireforming loads as with formed loads in my K-hornet.

I don't quite understand your premise, however. It sounds as if you've rechambered, but have not tried any actual K-hornet loads due to lack of dies. If this is the case, and your accuracy has deteriorated only due to the rechamber, then it indeed does not bode well for the ultimate outcome. However, it may be that your headspace is rather loose when using only the rim, and fireformed cases headspacing on the shoulder may tighten things up considerably. BE SURE TO NECK SIZE ONLY IN ORDER NOT TO SET THE FORMED CASE SHOULDER BACK. Let us know when your K-Hornet dies come in and you've had a chance to try some formed cases.