So you think the pressure is 37% more...?
Maybe not 37%.
Maybe 30%, maybe 60% in THAT barrel.
Dave's correct, from the info provided by Remington, we know nothing of the internal ballistics. Different powders have different burning rates with significantly different pressure profiles. That's why there is so much work involved in assembling re-loading manuals: internal and external ballistics are evaluated.
Actually shot-shells are easier than metallics because there are just 6, or so, gauges/bores. So, the labs needs only a small collection of test shotgun barrels. With metallics there are all of those different bullets in many, many different cartridges/calibers. Right now, there's probably some lab tech rigging a barrel to evaluate another new metallic cartridge.