+ 1 on that 'lock up check' without the forstock first, then,
Do you have a dial indicator?, If not, how about a set of feeler gauges?
What you should do is:
Open it
Cock it
While holding the hammer pull the trigger and let the hammer down to give its full firing pin protrusion (as it would be firing)
Measure the protrusion from the face of the standing breech (you can 'eyeball' this with the feeler gauge's in good light, stacking some if need be)
Tell us what you get
Next:
If the chamber is a bit deep you do not want to full length resize, only enough to get them to chamber up flush; back off the die and just kiss the shoulder established on the fired cases, then 1/4th turn more
This will keep those cases filling the chamber and may make your original frame work.