Anyone shoot Double Tap 41 magnum ammo in Your N frames? 170 and 210 grain controlled expansion JHP.

I bought a Model 57 a while back and got some ammo with it. There were a few boxes of DT. I think they were 310 grain. When we tried it out we thought there was a malfunction. Seems like there are two projectiles in each round.
Only shot a couple of cylinders though.