That’s a good question, and it’s smart to think about wall thickness before touching the cones. For most quality fluid steel 16 or 20 gauge barrels, many folks like to see a minimum wall thickness around .025"–.030" in the forcing cone area, with a bit more giving extra peace of mind. That said, every barrel is different—age, maker, and condition all matter. A proper measurement with a wall thickness gauge and, when in doubt, input from a competent smith is always worth it.