Lots of confusion here.
First, details, details. The Hodgdon limit of 5.3 grains is premised on a flat nose 230 grain bullet seated to 1.200" COL. Current Hornady data for the 230 grain XTP seats it to 1.230" COL. I don't know how the lengths of the two bullets compare, but suspect the XTP may actually be shorter as Hornady's maximum listed charge is 5.7 grains. This is using a Winchester LP primer which, as most folks know, is for both magnum and standard primers. Nonetheless, never start near a maximum. Always start at the bottom and work up. It usually proves unecessary, but just for those few occasions when going down that far turns out to be important, you still want to do it.
Different bullet makers also have different hardnesses of bullets. This changes pressure even when the weights are the same.
This Allan Jones article describes why. The Norma manual mentions test that got 30% pressure differences with different bullet types of the same weight all fired in the same gun with the same powder charge. So what was a limit with Hodgdon's bullet may not apply to the XTP.
Neither sets of loads are +P, so your gun should have some error margin, still.
Second, magnum primers are about gas quantity. A magnum case is generally larger than a standard case, and it takes more gas to pressurize the bigger space to adequate start pressure when using powders with heavy deterrent coatings, this is critical. But even with those that light more easily, if the case has extra empty space in it, a magnum primer can give you better start pressure consistency. But in a short case like the 45 Auto, it can also play tricks like unseating the bullet, thereby actually reducing pressure and velocity. Surf YouTube testers and you will find examples. Because of the ways in which different brands achieve magnum gas quantities in their primers, one brand can raise pressure while another lowers it. I won't get into the whys and wherefores here, but do be aware it can go either way. A good rule of thumb is to knock your load down 5% when moving to a magnum primer, then bringing the charge back up until you velocity matches the original velocity.
In 1989, CCI reformulated their magnum primers to better ignite slower spherical propellant process powders, which have very heavy deterrents. They make hotter sparks. Other makers followed suit over time. But there were magnum primers for pressurizing large capacity cases well before then.
231/HP38 is considered spherical because of the process used to make it, even though a lot of the spheres get flattened. All powders made by the St. Marks, Florida plant are in this category, regardless of actual grain shape. Take a look at some H380 if you want to see literally spherical grains, but the others made by this general process type are mostly what I would call granular in appearance. Whether you get grains of spheres has to do with drying rates. The Norma manual describes it if you are interested in the details.
