2 5/8 chamber and hunting

[Drew Hause]

Jeff: period documents confirm that many makers (Parker, Fox, Ithaca) cut chambers about 1/8 inch shorter than the paper case roll crimped shells for which they were intended.

There is no data suggesting an increase pressure using modern 12g 2 3/4" plastic hulls (many of which are slightly shorter than 2 3/4") in 2 5/8" chambers.
Using 2 3/4" shells in shorter than 2 1/2" 20g chambers is of concern however.

The other issue is that only after your Twist barrels have been evaluated by a gunsmith with the interest, expertise, and equipment (wall thickness gauge and bore scope) to properly do so could load advice be given.