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.

[Stan Hillis]

Originally Posted by Drew Hause

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.

The way the measurement is taken is after the shell is fired. I have picked up empty modern 12 g hulls and compared them and found significant variations in overall fired length. However, and this is important, while I have found many that were shorter than 2 3/4", some significantly, I've never found one that measured over 2 3/4".

Spend some time looking for and measuring fired hulls and segregate the shorter ones. Then, spend some time looking for stats on the loads, particularly looking for chamber pressures (which are hard to get your hands on). Then, choose a shorter load with a lower pressure and with lower payload and velocity and you'll be fine, provided your gun is sound.

Here's an example of a "before firing measurement". Note how much less than 2 3/4" the shell is. Then, notice that this is a vintage era 3" magnum load and only measures 2 1/2" loaded.