Wadcutter brass is not as strong
Some time ago I did quick check comparing the 38 Spcl wadcutter double cannelure brass walls to a 38 Spcl (+P)'s brass walls.
Using a .350" pin gage (the biggest that would pass by the inside ridges caused by the double cannelures), it would extend ~.725" into the sized wadcutter double cannelure case but only ~.460" into the (+P) case, a difference of ~.260".
That shows the wadcutter's straighter walls & the (+P)s thicker more tapered lower walls.
The wadcutter's walls only start getting thick just below it's lower cannelure while the (+P)'s starts getting thicker higher, where the upper cannelure would be on it, if it had one.
They're that way so that the hollow base of the fully seated soft lead wadcutter doesn't get deformed by the reduced inside diameter.
A typical 148gr swaged lead cutter has a bullet length of ~.616" long.
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