Mizuno Mp63 Play Short?

Not so for the JPX line. The 800 Pro's line up pretty well with everything else I've hit and the regular JPX [non-Pro] are said to be about 10-15 yds longer than the 800 Pro's. Just my n=1 experience, though.

Maybe the internal butter reservoirs weren't properly topped up during production? It happens.

I've hit the 800 Pros against the 53s and didn't see much difference in yardage between those. Will try the 53s against the 63s next time I'm at that range.

The JPX 800 is also a degree stronger than the JPX Pro, too. Did you notice a difference in feel/playability for the two? My dad is using MP33's, but considering stepping down to the new JPX line.

I haven't hit the jpx line but they market that the jpx 800 iron has a hotter face by making the face thinner for more trampoline effect. They ouldnt forge the iron because of the thin face

The 800 is VERY hot! I hit them, as well as the Pro's and 57's. I hit the 800's 20+ yards further than the 57's and about 10 yards further than the Pro's. I also didn't produce much backspin with the 800's and there was more shot dispersion on them. The 57's had the tightest dispersion and the Pro's the best combination of distance and dispersion of the Mizuno's.

yea I saw Luke Donald hitting them on the trackman compared to his mp irons and his ball speed was way faster and it was like 10 yards farther. Hes a pro though so his results are going to be more accurate than what someone ont he sandtrap might claim. He was like and why dont I have these in my bag, lol. Honestly though, I highly doubt hes gonna bag the 800's over their mp line. I wouldnt mind have a set of the 800's though if I had unlimited amounts of money to throw out on equipment

I would say the clubface has more to do with it than the loft difference. It being cast vs. the forged of the Pro is part of the difference between them. The thing that bugged me though was I could see part of the cavity at address, of course picking up some extra distance gives you less club in your hand. That is assuming that you keep them in play...

I went to a pro shop today and I hit some Mizuno irons, and to me the MP-58 was way shorter than the MP-62. The 62 had a longer shaft (with lines indicating the std length, which I tried to use), but even considering that the 58 were too short. I was hitting the 58 150 yds on a "good" shot, while the 62 was giving me 160 on a bad contact, almost 190 in a good one. I play MP-57, and I play the 6 iron for 170~175 yds.
The only explanation I can imagine is that for some reason I can't hit the 58s in the sweet spot, while with the 62s it was easier for me (isn't it supposed to be the other way? )

Both irons had PX 6.5s, with my current set being flighted. With a 6 iron in hand, I'd imagine the flighted set may fly a bit higher than the non-flighted club, however neither should produce a ballooning ball flight. Spin rates were pretty high with both (~9500 rpms).