[Willard]

A lighter slide would have difficulties, unless you used a stronger recoil spring, or a weaker magazine spring.
A quick look at the .22 conversion units will bear this out, as the slides are aluminum, and the magazine spring relatively weak. This is because the .22 doesn't generate as much force, so a stronger recoil spring wouldn't be needed.
Conversely, if you went from a 9mm to say a .357 Sig, which generates more force, you would need to use a stronger recoil spring, and depending on how much stronger the recoil spring would need to be, could also determine if a stronger magazine spring may be necessary.

If you are familiar with Wolff Gunsprings website, they don't recommend their 10% extra power magazine springs, unless you are using a stronger than factory rated recoil spring.

Your question about military use... when you go back to early "submachine guns" of "simple blowback design", either the bolts were so heavy, it made it difficult to hold steady sighting because of the reciprocating mass, or they required extra strong springs.
That's why you only see "blowback operated" firearms of low pressure ammunition, such as .22 S,L,LR, and .25 ACP through .380 ACP.

 

[HazeGrayJeep]

I see IPSC style guns with the cuts. In a game where miliseconds count, I can see it. But in a duty gun? Pass. And in a warzone, heck no!

 

[GCBHM]

They have absolutely no use to me. As a duty gun the only thing I can say the advantage would be is to make it lighter. Outside that, it also allows for dirt, gunk and grime to find its way around your barrel easier, which could cause stoppage. I'm sure advocates for the cuts will say that they also act as a drainage port, but at the end of the day, other than looking cool and making the gun lighter, they serve no useful purpose, especially on smaller guns like a Glock 19. On larger guns, like the long slide Glocks, sure, making that gun lighter is of some benefit, but honestly, it isn't at all necessary by my estimation. I've steered clear of the Glock 34, 35, etc. b/c of the ports. Just don't like them.

 

[bearone2]

visual only & i'd never buy a sig that had been modified.

 

[Trave1ingEast]

Anyone ever hear of a fellow named P.T. Barnum?

Yea, it's like that.

 

[chinch]

How beneficial if all are are slide lightening cuts (if at all) - (pick included). A lot of them seem like decoration, but I figured that their must be some benefit. Only things I can think of are (1) reducing overall weight (however slight), (2) reducing muzzle flip due to having less reciprocating mass over than hand.

- Are any of ^these^ true?

Yes. While not for me, but if i were shooting 5" (long) slides on plastic frames competitively or at the range i'd want the cuts for reason #2. Likewise for carry i could see someone wanting less weight (not a pocket pistol). No crime in that.

 

[boris95]

Slide cuts are used mostly for competition. Of course weight saving, but more importantly, lock up time. These pros are all about hundredths of a second. As far as muzzle rise, more weight up front is preferred or compensated.

 

[Papa Sig]

My glock 34 has the cutout on top of the slide. I believe it's to make the weight the same as a glock 17 slide because I believe they both use the same weight recoil springs. That's at least on my glocks. Others might have them done for weight or looks I guess.