Novice here and I've decided to start reloading. I decided that my first reloads are going to be 357 ammunition for my S&W 627-5 PC with a 5 inch barrel. I purchased Hodgdon H110 pistol powder. I purchased Winchester WSPM primers. I purchased Hornady 125gr HP-XTP bullets. I read the Hornady 8th Edition Reloading Handbook. Page 922 of the Hornady Reloading Handbook lists the setup criteria for their load suggestions. Hornady states that they used a Colt Python handgun with a 8", 1-in-16" twist barrel. Page 923 of the Hornady Reloading Handbook states that for their 125 gr bullets that the starting load for H110 powder should be 17.4 gr and the max load is 19.9 gr. The last sentance on page 922 of the Hornady Reloading Handbook states "Do not deviate from the printed data"

I went on-line and found the Winchester/Hodgdon Reloading Data Center. I was shocked what was listed as the starting and maximum loads for the 125 Hdy XTP bullet using H110 powder. Hodgdon data was based on a 10", 1-in-18.75" twist barrel. Hodgdon lists the starting loads as 21.0 gr and the maximum load as 22.0 gr. All kinds of Bells went off, Hodgdon's 357 load recipe contradicts the Hornady Reloading Handbook for start and maximum loads. Which manufacture should I follow? Is the lower velocities listed in the Hornady Reloading Handbook safer?

On the Hodgdon WEB site, lists a few warnings. " H110 and Winchester 296 loads should not be reduced more than 3%." What is Hodgdon's point of reference? The start or maximum loads?
"Reduce H110 and Winchester 296 loads 3% and work up from there. H110 and Winchester 296 if reduced too much will cause inconsistent ignition. In some cases it will lodge a bullet in the barrel, causing a hazardous situation (Barrel Obstruction). This may cause severe personal injury or death to users or bystanders. DO NOT REDUCE H110 LOADS BY MORE THAN 3%. "
Please help me understand this warning. I understand the H110 is slow burning powder and needs time to build pressure. I just don't understand the 3% limit. The difference between 22 gr and 21 gr is 4.55%. That exceeds 3%, if the point of reference is 22 grains. 3% from 21.0 gr starting load is 20.37 gr. Is 20.37 gr the minimum reduction for H110 powder? Do I now just ignore the information that is printed in the Hornady Reloading Handbook?