James,
Looks like my eye's missed the 3, earlier. Here's a
link to the SAAMI drawing with both inches and millimeters given. The CIP drawings can be
seen here (got to scroll way down) and their millimeter length matches SAAMI's. Lee must have typo'd.
That said, 0.02 mm conversion error doesn't mean beans in this context. My actual concern was you'd not got the bullet seated deeply enough for the case to have a good grip on it and to help develop adequate start pressure. Keep in mind that a .38 wadcutter is seated flush with the case mouth, telling you there's no real lower limit to seating depth as long as you have enough space under the bullet for the powder to behave and you work the load up that way.
I'd measure the bullet bearing surface length and seat that portion flush with the case mouth. If this were a fast powder burning well, I'd say you need to work the load back up to test it. But as you are below Vihtavuori's starting load recommendation of 5.9 grains of N350 for the 125 grain plated Ranier flat point bullet seated to 36.5 mm COL, I don't think you're in any danger. You're just running at pressures too low for the powder and maybe with bullet grip that is too light to let it start burning well.
Again, because of the short barrel I'd look at something faster. Vihtavuori doesn't list N310 in their loads with that Ranier bullet, but they do list N320, which I've found to be a good powder in .45 Auto. They recommend 4.5 grains as the starting load for the Ranier with that same COL, so you'll get more loads per pound with it, as well. I think you'll be much happier with it.