What you need to know about gapping your iron set

One of the best ways to make sure your golf clubs are optimized to shoot your lowest scores is to gap your iron set properly.

What does that mean? Well it can be great if you hit your 5-iron 215 yards in the air. But if you don’t hit your 6-iron at least 195 yards in the air, what are you going to do when you need to hit a shot that carries 195 yards?

Proper gapping can help you avoid having an awkward yardage where you’re in between clubs and either have to swing too hard with a shorter club, or try to take a lot off a longer club, thus reducing your stopping power.

With that in mind, I’ve been getting a few new sets of irons, so I figured I’d put a set through their paces by going through a gapping session and seeing what we can learn.

The tools (and the issue)

Last year, my gamers were a set of Mizuno Pro 241s, 243s and 245s. With the release of the new Mizuno Pro S-3, I’m now removing the 241 (the PW and 9-iron) altogether and using the S-3 to replace most of the 243s.

Why am I doing this? I hit the ball high with not a lot of spin, but plenty of speed. The S-3 is a more compact player’s cavity iron than the 243, which Mizuno dubs a speed cavity, a good name for a players distance iron that isn’t hollow (i.e. Titleist T150, Srixon ZXi5).

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The S-3 also has weaker lofts which will help me add a touch of spin and get my landing angles all above 50 degrees, which will help my stopping power on the greens.

That said, the S-3 is smaller and less forgiving than the 243 and in the longer irons, I know I’ll be more comfortable with the 243 or 245 (the hollow-bodied players distance iron) both from a confident look and ball speed retention.

So the question is, where do I need to make a break?

What are we looking for?

When you’re gapping your iron set, there are four metrics to pay attention to (three more closely): Ball speed, apex height, landing angle and ultimately, carry distance.

Your goals are to have roughly 5 mph ball speed gaps throughout the whole set, apex heights that are all about the same for each iron and a landing angle that is above 50 degrees.

If you can check all three of those boxes, that should leave you with clubs that give you optimal 10-15 yard gaps in carry distance that you’re able to stop on a green.

Why are we not worried about total yardage? Because total yardage depends on the ground conditions which are constantly changing, whereas carry distance only depends on the air density and wind, something you can more easily adjust for.

I’m also not looking at horizontal dispersion as I know I regularly can hit my target on the course with these irons, that’s not what I’m worried about. I suffer greatly from parallax distortion on an indoor simulator. That means I just can’t get as comfortable in an indoor box off fake turf as I do on a real golf course, which can lead to more bad swings than normal, what I like to call “simulator shots.”

Lastly, you should also look at ball speed consistency because it’s no good if you get to an average of 130 mph by having one at 130, two at 125 and two at 135.

The results

Conducted on Trackman with four shots with each club.

9-iron: (Mizuno Pro S-3) 42 degrees of loft, 61.5˚ lie (-1.5˚) ,36.25″(+.25″), Project X 6.5

Ball Speed: 116.5 MPHConsistency: ±1.5 MPHApex Height: 122Landing Angle: 56.2˚Carry: 150 yds

8-iron: (Mizuno Pro S-3) 38 degrees of loft, 61.0˚ lie (-1.5˚), 36.75″(+.25″), Project X 6.5

Ball Speed: 121.9 MPHConsistency: ±0.5 MPHApex Height: 126Landing Angle: 55.5˚Carry: 161.9 yds

7-iron: (Mizuno Pro S-3) 34 degrees of loft, 60.5˚ lie (-1.5˚), 37.25″(+.25″), Project X 6.5

Ball Speed: 127.5 MPHConsistency: ±2.0 MPHApex Height: 130Landing Angle: 55.2˚Carry: 173 yds

6-iron: (Mizuno Pro S-3) 30 degrees of loft, 60.0˚ lie (-1.5˚), 37.75″(+.25″), Project X 6.5

Ball Speed: 131.9 MPHConsistency: ±1.4 MPHApex Height: 128Landing Angle: 53.2˚Carry: 188 yds

5-iron: (Mizuno Pro S-3) 27 degrees of loft, 59.5˚ lie (-1.5˚), 38.25″(+.25″), Project X 6.5*

Ball Speed: 136.4 MPHConsistency: ±2.6 MPHApex Height: 127Landing Angle: 51.4˚Carry: 201.4 yds

5-iron: (Mizuno Pro 243) 25 degrees of loft, 59.5˚ lie (-1.0˚), 38.25″(+.25″), Project X 6.5*

Ball Speed: 140.2 MPHConsistency: ±1.1 MPHApex Height: 117Landing Angle: 48.2˚Carry: 213.5 yds

4-iron: (Mizuno Pro 245) 21.5 degrees of loft, 59.0˚ lie (-1.0˚), 38.75″(+.25″), Project X 6.5*

Ball Speed: 143.3 MPHConsistency: ±1.0 MPHApex Height: 117Landing Angle: 47.7˚Carry: 219.7 yds

The Findings

As you can see, everything is right on the money with 12-15 yard gap in carry yardage and peak heights in the 120-130-foot range with my set until we get to the 5-iron. While the carry number is OK, the ball speed isn’t there with the Pro S-3 5-iron and the consistency is well… inconsistent.

For this test, I also brought my old Pro 243 5-iron, which went a bit too far and didn’t quite fly high enough.

When it comes to the S-3 5-iron, it just simply is too small to the point where I can strike it well when I make good swings, but it’s not going to help me very much on my bad swings. This is where we come to a point of diminishing returns.

The 243 goes too far, but I hit it way more consistently as it’s slightly bigger. The kicker here is that the 243 5-iron is 2 degrees stronger than the S-3 5-iron, so the natural solution is to weaken the 243 from 25 to 26 or 27 degrees, whichever allows me to consistently hit a 205-yard carry and reach a 120-plus-foot apex height.

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I may also weaken the 4-iron half a degree to 22 degrees just to get the launch up a tad and keep the carry under 220 yards. Anything past that, and that’s where my 3-iron (still tinkering with this one), 3-hybrid or 5-wood come into play which give me 235-240 carry.

Weakening the 4-iron to 22 and the 5-iron to 26 also gives me constant 4-degree loft gaps through the entire set, which isn’t necessarily the goal, but the thought is, consistent gapping will come from consistent lofts too, which appears to hold up based on my data.

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Takeaways

I am lucky enough to have access to both a Trackman and a loft/lie machine, so I can make all of these adjustments myself. But if you don’t, a gapping session is something that will be well worth the investment in your game.