A lighter slide has less felt recoil to start with.
And I believe being the G34 is a 'target' pistol this is why the slide is slotted.

Gaz

 

It was always my understanding that the cutout was so the slide weight would be the same as a G17 slide. True or false, I don't really know, but it sounds good to me.

 

Although I couldn't confirm this after going to the Glock site ... this appears to be the reason. With the same mass as the G17 slide the RSA springs could be interchanged. I don't have either, but if there's someone on the forum that has access to the part numbers it could be confirmed.

 

"Save for the optics cut, the Glock 34 MOS is virtually identical to the Glock 34 Gen 4. The barrel is 5.31 inches long. The slide has one large port, to keep the upper assembly mass closer to the Glock 17's, as to not require as much fiddling with recoil springs for timing. The factory 17 pound recoil springs are interchangeable between the Gen 4 Glock 17 and Glock 34. The recoil spring assembly has a captive polymer guide rod wrapped with dual-springs, a feature of Gen 3 subcompact and all Gen 4 Glocks."

I'm quoting from the following blog: Glock 34 MOS 9mm Trijicon RMR Review - The Very Traumatic YouTube Blog?

 

I don't have a 34 but I have 17L. On my trusty harbor freight digital scale the 17L slide weighs 13.2 oz.,the 17 slide weighs 12.6 oz. The 17L and the 34 are similar with the large hole in the top of the slide. Hope this helps.

 

Balance also plays a part. That small amount of extra weight out on the end of the longer slide would be very noticeable.

The G40 doesn't have the material removed from the slide. After handling it and comparing with the G20 I decided to not buy (waiting to see if they release an MOS G20).

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