I'm thinking about transitioning my G17.4 into the HD role tonight; the mag in the gun wears an OEM +2.
Taking Glocks advice, the mag has the 11 coil spring (33601) in conjunction with the OEM +2 (7151/7165).
The magazine only has a few cycles, but it has performed as expected with both FMJ and HP ammunition.
Seeing as how it is an OEM extension, using the recommended spring, and Glock is shipping the 19X with two mags in this configuration, I inherently "trust" the combination as it appears to be thoroughly vetted.
Generally speaking, how many rounds must you put through a magazine with an extension, OEM or aftermarket, before you trust it?
For those of you who don't trust ANY extension,. I can understand that too.