Slide velocity...

The 115gr Blazer Brass I was shooting was the typical low-powered budget fodder. In the Glock 34 MOS, spent brass would often pop six inches straight up out of the ejection port and land at my feet. It was no great challenge to keep the dot in the window and on the target all the way through the recoil cycle.

And yet the same ammunition from the same lot cycled the slide on the diminutive P290 vigorously enough that spent cases were landing six or eight feet behind my right shoulder.

Slide velocity in these micro nines can be an issue if you're running hot +P ammo, because sometimes the magazine spring can't get the next round lifted into place in time.

Anyway, Wednesday I fired another fifty rounds through the gun with no malfunctions. This makes 200 rounds fired with no malfunctions. 1800 rounds to go.
.