How the Mizuno ST230, JPX 923 and S23 clubs helped this handicap 1

The author plays a shot with a Mizuno JPX 923 Tour 8-iron.

Jack Hirsch/Golf

Welcome to the ClubTest Proving Ground at, where Managing Equipment Editor Jonathan Wall and Senior Equipment Editor Ryan Barath – along with a team of GOLF writers and editors – put the latest designs and ground-breaking technologies in the equipment space to the test on the range and class. For the 2023 ClubTest, we’ve paired our staff members with the latest equipment from the manufacturers to give you, the potential club buyer, a “real feel.”

Test: Jack Hirsch (Assistant Editor). 1 HCP

Goal: Discover more precision with the driver, consistency and playability with irons, and versatility with the pegs.

Bottom: Although I never fulfilled my childhood dream of getting a college golf scholarship and getting on the PGA Tour, I’d like to think I’m not laid back on the golf course. After all, I grew up around the game with a father in the golf industry, and in a family of three avid golfers.

Of course, working full time made a dent in that, and these days I’m about to handicap one, but there’s certainly potential for a return to sanctuary as well as a handicap if I can add a little consistency back into my game. My clubhead speed isn’t crazy fast—around 111 to 112 mph, but I’m used to being in the longer half of a quad. What comes at that speed is a bit of wildness and a very loud launch. It’s interesting to think about how when I was professionally fit for golf clubs the first time in high school, I was put into a high launch launch shaft, but the second time around, while in college, I was into extra stiff, low launch product and since .

With irons, I’ve never played anything but forged clubs with fairly fine lines. Once I grew out of American children’s golf clubs, my dad built me ​​a set of Ben Hogan Apex Pluses from the late ’90s and I’ve used a similar head ever since. Thin sole and narrow sole, but fairly full bore in the racquet. I definitely benefited from the use of new technology and materials in my previous set of irons that allowed for smaller profile features with greater perimeter weight.

The pegs are the most important to me as you can tell from my description above, I didn’t hit them very far until college, and because of that, I didn’t hit them right. But I can go up and down anywhere. My creativity around greens has always been my strength. This was despite not wanting to use any wedge makeup other than the 52 degrees and 58 degrees. I thought I could hit any shot I wanted with this setup.

With all that said, I also grew up as a wannabe gearhead. My dad always had a hobbyist club-making setup in our basement or garage where we do grabs, remodels, etc. I had one, and I know how to check and adjust the flat top and lies as needed.

My equipped equipment:

The author plays a screenshot with a Mizuno ST 230 Z driver.

Jack Hirsch/Golf

Driver: I was fit for Mizuno’s new ST-Z 230 driver. This is the bottom spin of their two models, is slightly open in heading (a common preference for a better player) and features a slightly more pear-shaped head and lacks the intake bias of the ST-X. Both drivers feature Mizuno’s signature hot-swap switch mechanism, which allows for 4˚ of loft adjustment. I had a 9.5 degree head, which I bumped up to 8.375 degrees, similar to my player who had a 9 degree head I used to play either 9 degrees or 8.25 degrees.

The crown jewel in the line is the new CORTECH chambering that Mizuno says is the “missing piece” to help elevate their woods from the shades of their irons. The chamber is a molded stainless-steel, TPU-coated weight (that stuff you don’t know if it’s rubber or plastic) that sits on the sole, just behind the face. Mizuno said it allows for greater flexibility of the sole, resulting in increased ball speed, along with sound, and improved feel.

What I found, though, was a “top-of-the-line” head-up, the new ST-Z was incredibly forgiving. My top ball speeds averaged across the test between the ST-Z and the Toy Drivers (which was the 2022 model I loved), but my average ball speeds were more than 1 mph faster with the ST-Z (164.2 vs. 163.0). Not only are the ball speed numbers more forgiving, but the dispersion is also more forgiving (as you can see from the shot chart below). I’d cast a narrow tie easier.

The author got distracted with a Mizuno ST-Z 230 (red) and game driver (blue).

Jack Hirsch

The driver’s forgiveness was also proven at the track when he somehow found a horrible swing midway (I have witnesses). Check out the impact website below.

Believe it or not, that ball, hitting the toe, found the center of the fairway.

Jack Hirsch/Golf

Fairway Timbers: I’m one of those guys whose slightly older Wood 3 makes them shiver in their shoes when they see it. It may not be a Tiger Woods eight-iron from 2000, but my 3-wood is the closest I’ve ever come to “knocking off” the club’s sweet spot. I want to have 3 high (13-14˚) strong woods that I can mash from the tee and get to the 5 tallest greens in 2 splits. My next club down, whether it’s another Fairway wood or a 2/3 hybrid, is something more versatile for playing outside the rough or stopping faster on hard greens.

The ST-Z 230 3 and 5 match woods fulfilled both of these needs for me. The clubs again feature new CORTECH room from the driver and some additional weight in the back of the head to promote a higher launch. The ST-Z (no ST-X option this year) doesn’t come in stronger than 15˚, but with 4˚+ loft adjustability this wasn’t a problem, as I was able to lower one setting to 13.375˚ and get a second driver which I love (At a wrecking ball’s speeds of 160 mph!). It also has a touch more of a spin, which gave me a nice boost of control and versatility.

I was a bit skeptical playing with a fairly large head (177 cc) compared to a 5-wood (140 cc). However, the improved head weight and launch characteristics allowed me to get balls out of any lie I could with a smaller club and the flight hit the exact window and bore. Combined with the adjustability to make the 18˚ 5″ wood as strong as wood 4 or as soft as wood 7, this club can be whatever the course.

iron command: I fit a Pro Fli-Hi 3 iron to switch with a 5-wood. This club is a bit more fleshy than my previous driving iron, but the black color helps hide the bulk and I’m actually able to get a little more ball velocity thanks to the MAS1C’s steel face, the same material used on the Mizuno Fairway woods.

Mizuno JPX923 irons are forged and round.

Mizuno Golf

Medium/long irons: In the interest of complete transparency, I was so dizzy to draw Mizuno for the clubtest. The only two sets of irons for adults were Mizuno irons, and my dad’s basement is a treasure trove of classics including MP-30s, MP-60s, MP-52s, JPX-800 Pros, and more. For the rest of my irons, I went with a separate set from the new JPX 923 line. This year’s line features five models, which fit in very well with last year’s three Mizuno Pro models. The other three game-improving models (JPX 923 Hot Metal Pro, Hot Metal and Hot Metal HL) are released in the fall while the JPX 923 Forged and Tour are released at the beginning of the year to give each line time to shine.

For my 4 to 7 iron, I tried the JPX 923 Forged. These irons can fit between the Mizuno 225 and 223 irons as a forged rear bore that delivers the fast ball speeds of the hollow-body model (225), but fit in a smaller profile such as the muscle bore (223).

Mizuno’s new V-shaped construction has helped allow the topline of these irons to be thinner than ever, while retaining that classic Mizuno forged feel. The Forged also forms a micro-hole behind the face in the 4-7 iron that helps speed up the juice ball. This is a technology borrowed from the Hot Metal family. I’ve finally been able to look at an iron that gives you more tolerance and ball speed while maintaining the compact shape I love.

With these irons, I’ve noticed a 1-2 mph bump in ball speed, while I’ve also seen slightly higher and higher spin numbers. This finished off which meant that these irons flew a few yards farther out of my old hands while stopping faster. The overall distances were similar, but if I could get more of that number through the air, rather than rolling, while still being able to smash it, I’d take it.

short irons: From an 8 iron to PW, I have the new JPX 923 round. These are like daggers. Mizuno has created a cavity back iron with a muscular back-like feel thanks to its “Harmonic Impact Technology.” You’d be forgiven if you thought you were whacking a conventional blade when swinging the 923 Tour before realizing that the sweet spot is actually a reasonable size. As a pure irons player, these clubs allow me to run the ball in any direction I like and the slight groove gives me some wiggle room with errors. The microslot technology in the Forged and other JPX models is not present in this one, but that technology is not in the scoring iron in the JPFX 923 Forged either, which makes going from 7 to 8 iron the logical place to break out the set.

I shouldn’t need to break up the classic Mizuno feel here, but it just might be better than ever with a copper base layer, a first for a JPX iron. These irons allow you to get pinpoint accuracy in crafting your shots, but allow just enough wiggle room for the bad guys to be playable.

The author plays a shot with a Mizuno S23 sand wedge.

Jack Hirsch/Golf

wedges: Perhaps the biggest surprise to me were the new S23 wedges. I’ve never been one to venture outside of traditional forms. So when I saw a hollow back wedge similar to the 2015 Nike Engage, I thought it would be more targeted to mid-to-high hand users than I am. I was very wrong.

The hollowing allowed Mizuno to move the center of gravity toward the toe, where most shots are hit around the green. Not to mention, these wedges use the same shaping method as Mizuno irons, which makes for a very consistent feel to the iron.

The S23s are designed to flow smoothly from the JPX 923 forged irons I have at the top end of my range, but I see no reason why they wouldn’t do as well from the JPX 923 rounds I have.

For the first time for me, I swapped my 52˚, 58˚ gap (with a 62˚ thrown in there recently) to a 50˚, 55˚, 60˚ setting to help even my full swing gaps given the 62˚ wasn’t very useful outside of 30 yards.


While I didn’t make huge gains in distance, I still saw huge performance gains in terms of dispersion and consistency. This wasn’t the first time I’ve been fit professionally so seeing the improvements over my previous set will be tough, but it’s safe to say mission accomplished.

With the ST-230 line and the JPX 923 line, Mizuno has proven two things: 1. The JPX line has as much to offer better players as it does for beginners. 2. Mizuno drivers can step out from behind the shadows of the most popular iron offerings. I now have a driver I’m as confident in finding the fairway as I attack flags with irons.

Mizuno irons are again a great option for anyone looking to upgrade, but this year so is the driver.

Want to fix your bag for 2023? Find a suitable location near you at the GOLF affiliate True Golf spec.

Jack Hirsch editor

Jack Hirsch is an assistant editor at GOLF. Born in Pennsylvania, Jack is a 2020 graduate of Penn State University, with degrees in broadcast journalism and political science. He was captain of the golf team in high school and is still *trying* to remain competitive among the local amateurs. Prior to joining GOLF, Jack spent two years working for a television station in Bend, Oregon, primarily as a multimedia journalist/reporter, but also producing, anchoring, and even presenting the weather. He can be reached at

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