FO sights are bright, and a typical install has a chosen color for the rear two dots and a second color for the front sight. At first this seems really helpful for alignment in decent light.
In truth, iron sights are not easier to align because of bright colors or large size. Proper, consistent presentation based on stance and grip (eventually just grip) aligns sights consistently. A wide black rear notch with a narrow front black blade has been known for speed and accuracy for many, many decades. They are bomb proof, never failing. Just the ticket for a SD gun.
Even three dots are unnecessary and a bit of a handicap when one considers the dots are all the same size so the front appears smaller being farther away. Concentrating on dots rather than the blade in the notch is an aid to beginner shooters, but it is not any faster or more precise than straight black irons properly aligned.
As to porting to supposedly reduce muzzle flip for faster follow up shots, it is more of a liability than an aid. Hot gases and bullet shavings being expelled from a 3.1”, or even 4” barrel, have a minor positive effect in 9mm, but shooting from closely held retention often puts those gases up into the shooter’s face.
In SD the gun may need to be held in odd positions because of the close range fight. The juice ain’t worth the squeeze given that proper grip for 9mm can provide the same benefit for recoil flip control, especially with a 4” vs. a 3.1” barrel. Porting is an extra expense that increases cleaning time and complexity, and depending on ammo can be really distracting shooting in the dark.
I’m not aware of any gunfights where porting was the major contributor in the win. I have a .44 magnum with a ported 6 3/8” barrel, and that porting definitely makes the gun easier to shoot. It goes paper shooting and plinking at extended arms position and I like it (black iron sights) and it shoots well at full extension. Porting has a place, but not in small, closely held self defense guns. Such holes allow fouling to get into the barrel also while carried.
If the goal is a series of faster aimed shots with a 9mm, improve grip and presentation consistency and you will achieve it with less expense and danger.
This consistent presentation/alignment is what makes red dots work so well. Properly aligned iron sights in the lower part of the RDS screen will produce the dot in the window. The dot anywhere in the window applied to the target, ignoring any slight misalignment of the irons, gets a hit. There is more room for accuracy, faster and easier. That’s self defense shooting.
The irons should disappear (be ignored) when using an RDS. They are harder to ignore when there is an array of four (colored) dots floating in the screen. Plain black irons are better.
So, IMO a Shield 4” 9mm, no thumb safety, typical three dot sights blacked out or replaced, no porting, cut for the Shield RMSc footprint red dot, sets up a useful, rugged, simple self defense gun with improved ballistics, better balance, longer sight radius (compared to 3.1”) especially if it is a Plus.
S&W doesn’t offer it. But you can make one of theirs into yours by investing some money and time for proper sights, RDS cut and optic. This is what S&W should offer. Porting, FO sights and cheap RDS make their offerings into less useful range toys. Too bad they don’t understand that the Shield line is primarily a self defense gun, not a range toy.
