is it possible for my vanguard to be approaching max pressures when the load isn't?
Absolutely, yes.
Every rifle behaves a bit differently. Test barrels are generally tighter than production barrels and generally produce slightly higher presures - but not always.
Yours is a perfect example of why I HIGHLY recommend reloaders use chronographs, which are available for as little as $49.95 for a refurb Shooting Chrony (call the factory).
As a general rule, you should approach maximums cautiously and STOP when one of two things occurs - a) you reach the maximum listed powder charge or, b) you reach the maximum listed velocity. You should always STOP also if you see signs of high pressure, regardless of what the charge or velocity is. Also, be aware that ANY deviation from the load recipe can cause dramatic changes in pressure. If you have changed the manufacturer for the brass or primer from that specified by the recipe, be extra cautious. Changing the brand of bullet can also make a considerable difference, although I find this less of a problem in most cases. Different lots of powder and/or primer can - and often do - have a significant effect as well. Again, a chronograph is HIGHLY recommended.
Over the years I have found that some loads reach maximum listed velocity well before I reach maximum listed powder charges. Other times I have found I couldn't overcharge the case enough to reach maximum listed velocity (ar anything near it) even if I wanted to because I run out of powder room in the case first.
For what it is worth, my powder charge is 35.0g Varget for 50g V-MAX bullets, Federal brass, CCI 250 primer..