1. Early TC Contender frames have the trigger guard hinge pin (not the barrel hinge pin) located at the very front of the frame. This was so that a dumbell-shaped roller on the locking bolt could ride up some sloped steel rails to compress the locking bolt. There wasn't much leverage to this setup but, they were running pistol and 22 LR cartridges and the locking bolt spring didn't need to be very strong. At some point the locking bolt was split in two halves to make it easier to open.
2. Later frames had the trigger guard hinge pin almost directly above the trigger. This gave more leverage so that a stronger locking bolt spring could be used... Which made it possible to run more powerful cartridges like 30-30.
3. TC offered an upgrade to the old frames through their Custom Shop. This upgrade is no longer available.
4. Fortunately, older barrels could be upgraded by just installing a stronger spring in the locking bolts.
5 UN-fortunately older barrels with strong spring locking bolts have difficulty in older frames that weren't upgraded.
a. Older frames do not have leverage to handle the stronger locking bolt spring.
b. Solid Locking bolt does not break open as easily as split locking bolt.
c. The newest locking bolts have solid buttons in place of the original dumbell roller... Too much friction for older frames.
Possible Solution - Find a latest version Contender frame but not a G2 version. This will run best with old and new barrels.