Improvements over the previous generation appear to be fairly minimal, but if you’re irons are a few years old then the JPX921 range should be high up on your list as a potential replacement because there is a model for every type of player that looks the part and has the performance to match.
A comprehensive range catering for all player types
Excellent feel and looks
Progressive levels of forgiveness
Ability to blend models within a set
Relatively small gains over the prior generation
Not much difference between Hot Metal and Hot Metal Pro models
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Mizuno JPX921 Irons Review
Watch Joel Tadman test all four Mizuno JPX921 irons on the golf course
You can read about the advances in technology and design here over the JPX919 irons but in the JPX921 irons, Mizuno has essentially created a range that caters for every ability of golfer. It claims the JPX921 Forged model will provide the most significant gains over the previous JPX919 model. We were lucky enough to be one of the first to give them a thorough test at Burghley Park Golf Club.
Changes in the design of each of the irons means Mizuno has made adjustments to the lofts. The Forged, Hot Metal and Hot Metal Pro are all one degree stronger in the 4-8 irons while the Tour model remains unchanged at 34° in the 7-iron. We tested all four irons on the Flightscope X3 launch monitor in the same Dynamic Gold 120 x100 shafts we tested the JPX919 models in.
Looks wise, there isn’t a huge departure from the prior generation. There’s more black paint fill on the back, which we think adds to the shelf appeal and the overall aesthetics are consistent across all four irons. The Tour model has a lighter finish than the old version and the Forged iron has been made more compact with a thinner topline than the JPX919 version, making it look more like the Tour than the Hot Metal Pro. As such it made it into our guide on the best compact mid-handicap irons (opens in new tab).
In all honesty, from the address view it was difficult to tell which was the Hot Metal and the Hot Metal Pro. We expected the Hot Metal Pro to be noticeably more compact, especially given the more refined look of the Forged iron. Performance wise, the launch monitor threw up a few surprises. The first being that the Hot Metal Pro gave us the fastest ball speeds and highest flight while the new Forged model actually spun the least.
We didn’t see as big a jump in ball speed and distance either from the old Forged model to the JPX921 Forged version. That said, the new model did launch higher despite being one-degree stronger in loft and provided 500 rpm less spin, which is no bad thing given these irons generally are quite high-spinning considering the lofts. We saw a nice progression in performance moving from the JPX900 Hot Metal through the JPX919 and then a bigger jump into the JPX921 version, although the lofts are getting stronger by one degree each time.
To further validate what the launch monitor was telling us, we took all four irons plus the old JPX919 Forged iron to a par three and hit two shots with each from the deck to assess feel, sound, flight and distance in a more realistic environment with Titleist Pro V1x golf balls (opens in new tab). To a flag 172 yards away and into a slight wind, the Tour model unsurprisingly came up short but the distances were consistent and dispersion accurate. The JPX921 Forged seemed to fly on a stronger flight than the old version, resulting in longer carries by 3-4 yards.
Once again, the Hot Metal and Hot Metal Pro produced similar distances although it looked like the Hot Metal sent the ball a fraction higher than its more slimline namesake. It’s interesting that just like the previous range, Mizuno (opens in new tab) hasn’t tried to achieve distance through low spin. The relatively high spin across all four models should help keep the ball in the air and stop it more quickly when it lands. Into the wind, the flight did look like it wanted to climb at times, but a switch in shaft via a fitting would go some way to negate this if it is something you experience.
Feel wise, there was a nice steady progression from buttery soft yet solid in the Tour model to more explosive in the Hot Metal with the Forged somewhere in between but closer to what the Tour offers. That short, thud sound from the Tour model was especially pleasing on the senses but it did lack off-centre forgiveness at times, making the Forged model a potentially more appealing prospect for the single-figure golfer, although the strong lofts may cause gapping issues at the wedge end of the bag.
The Hot Metal options produced excellent distance but more importantly were very easy to hit. Slight heel and toe strikes didn’t seem to effect the flight too much and there is more than enough launch assistance for slower swingers looking for extra carry.
All in all we were very impressed with the performance throughout the JPX921 range to the point they featured heavily in our best golf irons (opens in new tab) guide until they were replaced with the JPX923's. Additionally if you want more iron buying advice, be sure to check out our guides on the most forgiving irons (opens in new tab), and best distance irons. (opens in new tab)
Joel has worked in the golf industry for over 12 years covering both instruction and more recently equipment. He now oversees all product content here at Golf Monthly, managing a team of talented and passionate writers and presenters in delivering the most thorough and accurate reviews, buying advice, comparisons and deals to help the reader find exactly what they are looking for. So whether it's the latest driver, irons, putter or laser rangefinder, Joel has his finger on the pulse keeping up to date with the latest releases in golf. He is also responsible for all content on irons and golf tech, including distance measuring devices and launch monitors.
One of his career highlights came when covering the 2012 Masters he got to play the sacred Augusta National course on the Monday after the tournament concluded, shooting a respectable 87 with just one par and four birdies. To date, his best ever round of golf is a 5-under 67 back in 2011. He currently plays his golf at Burghley Park Golf Club in Stamford, Lincs, with a handicap index of 3.3.
Joel's current What's In The Bag?
Driver: Titleist TSR3, 9°
Fairway wood: Titleist TSR3, 15°
Hybrid: Titleist TSi2, 18°
Irons: TaylorMade P770, 4-7 iron, TaylorMade P7MC 8-PW
Putter: Evnroll ER2V