Duffy;
It sure sure sounds like to me that you are pushing the shoulder back slightly when you are resizing. I never full lenght resize - I either neck size only or partial-length resize. I think in a cartridge like this it is impertative that you do not touch the shoulder with the sizing die, it will push it back and cause case stretching problems. These cases are very thin and they can only stretch so much. Originally the hornet headspaces on the rim, but on the conversion you will want to make sure that you move the head spacing to the shoulder. Be VERY careful with the sizing die - the cases are very thin and you really cannot 'feel' the shoulder if you hit it. Set you die up by backing it out, smoke a case neck and screw the die down until it is just off the shoulder.
As far as velocities go - I can only go by the reloading data tables. I keep the loads just down from max because that is what my gun likes. This cartridge operates in the 35,000 cup range so I don't push it real hard. Serria has some good reloading data for this cartridge and so do the Contender reloading book.
If you have a ball micrometer and C-Mic you can measure your chamber and compare it to the K-Hornet drawings. It is not difficult to do, any smith should be able to help you with this if you are not entirely confident with your skills. Then you would know exactly where your Chamber parameters are.
My rifle has a bit of an oversized chamber and I have had no problems with it. The smith had to oversize it very silghtly to get the chamber rounded and trued, he did a good job and it works great.
Dave
