Mizuno JPX 921 Hot Metal Irons Review – Chromoly To The Third Power

Through 10 years of JPX innovation, Mizuno has broken major ground when it comes to their golf irons. One of the most important milestones is the use of Chromoly material. With the JPX 921 Hot Metal and Hot Metal Pro irons, Chromoly enters its third generation and Mizuno has unlocked its full potential. Chromoly to the third power means faster ball speed, incredibly straight flight, and controllable landing angles to hold more greens. See how it all works in TGW’s exclusive video and review.

Mizuno JPX 921 Hot Metal Irons Review by TGW

Technology

Mizuno JPX 921 Hot Metal irons start with 4140M Chromoly material. This is the third generation of irons from Mizuno to use Chromoly and now they have taken it to the limits. The club face is a seamless cup design that is thinner overall at just 2.2mm. They have also re-engineered the variable thickness CORTECH face so it is 0.2mm thinner at the center point. That promotes a faster, hotter impact to help boost speed and distance.

Mizuno included the Stability Frame structure in the new Hot Metal models as well. This design adds perimeter weighting with toe bias. That added weighting increases stability and forgiveness, especially on shots that you don’t hit directly in the center of the club face.

JPX 921 Hot Metal irons feature a new variable thickness sole as well. This allows the leading edge of the iron to act as a hinge, increasing face flex and increasing ball speed and energy transfer at impact. 

Finally, Mizuno added 3 additional sound ribs in the frame of each club head. Mizuno’s research into predicting vibration patterns led them to add more sound ribs in their Harmonic Impact design to produce a more solid feel when you hit the golf ball.

Performance

To test the performance of the Mizuno JPX 921 Hot Metal irons, we enlisted the help of Rick Hatfield. Rick is the head golf pro at Flint Hills National Golf Club and TGW’s resident product expert. While swinging a 7-iron at 83 mph, we saw the highest ball speeds out of any of the JPX 921 irons with the Hot Metals at an average of 115 mph. That translated to an average carry distance of 166 yards. The spin rate was around 5,500 rpm with a peak height of 80 feet that will land softly and hold the green from a 7-iron distance.

Who It’s For

Mizuno’s JPX 921 Hot Metal irons are the game improvement entry into the JPX 921 lineup. They feature all of the distance and forgiveness technology to provide faster speed, greater distance, straighter shots, and high launch. Golfers who like the look of Mizuno irons with that type of help will love these golf clubs. For players who prefer a more compact iron with less offset, they also have the Hot Metal Pro irons. The technology and features are all the same, just packed into a smaller club head with reduced offset for a little bit better golfer.

Appearance

Mizuno JPX 921 Hot Metal irons are game improvement irons. They feature a more prominent cavity back design with added perimeter weighting that looks forgiving and inspires confidence at address. The Hot Metal Pro design is a bit more compact and has less offset for the player who prefers that type of look down by the ball. Each set is then finished off with Mizuno’s signature pearl brush finish that reduces glare to minimize distractions.

Feel & Sound

The Mizuno JPX 921 Hot Metal irons have a solid, satisfying feel and sound at impact. Unlike the rest of the JPX 921 iron family, the Hot Metal and Hot Metal Pro golf clubs are not fully forged so the feel is a bit different. Thanks to the Harmonic Impact design and additional sound ribs, Mizuno has fine-tuned the vibration and feedback for pleasing feel and sound in a game improvement iron.

Mizuno JPX 921 Hot Metal Pro Irons