.357 magnum load help (rifle)

[6MT]

Ok fellas, I'm going to ask. I want try try 5 different charge weights in my new Winchester 1873. The bullets are lighter. They are XTP's in 125gr. The powder is H110. The barrel is a 20" with 1:18.75" twist. I know... I could do with the 158's, but I came into a lot of the lighter weight XTP's.

The brass is virgin Starline and I'm using Federal small pistol magnum primers.

The Hodgdon reloading data pages show a minimum charge weight for H110 of 21gr and a max of 22gr (rifle) for the 125gr class of bullets. Lyman regurgitates the powder manufacturer's data verbatim.

Sierra shows the min at 17.5gr and max at 19.3gr. Hornady shows a min at 10.4gr and max at 19.4gr.

Here's my plan. I loaded 5 rounds each of 16.0, 16.5, 17.0, 17.5, and 18.0gr. I know that H110 is best suited as a high end (read max charge or close to) powder. Kind of all or nothing. The cases are no where close to being full with the bullet seated.

Am I asking for some dangerous pressure spikes with the cases not being full or close to (volume wise, not charge wise)? Am I asking for a squib with the lower charge weight? How will the light duty toggle action in the 1873 react?

I need some help folks. Some guidance. I had great success with my Henry BBS in .44mag with H110. In fact I went about the load development the same way.

Or am I just over thinking this?