I believe the R&M formula [as shown in Kellogg]is :-
Radial force = 3.25 [D+3]^3
Shear forces at shell = 1.5 [D+3]^3
Moments = 60 [D+3]^3
D in inches and results in lb and in-lb

Now these values are usefull in SPECIFYING equipment allowables, but cannot be used with any certainty in assessing the loads on existing equipment where the allowable loads are unknown. There are many many different flavours of these formulas.
For instance Norsok requires
F = 7.5x(DN)1.2+0.1xPNx(DN)1.2[in N][for 16" 300# = 29840Nm {3042kg}]
M = 4x(DN-25)1.4+2x10-5xPNx(DN)2.7[in Nm] [for 16" 300# = 47880Nm {4880kg/m}]
PN in bar and DN in millimetres.
-Norsok at least makes an allowance for pressure, as typically a higher pressure system will have stiffer piping and thicker vessel walls, so can generate higher loads, but equipment also usually have the capacity to absorb them.

All these formulas [and there are many more] are useless in assessing loads on a vessel where the allowables are unknown. At best they are a guide. The only reasonably way to do it is to include the internal pressure, vessel wall thickness, diameter, material properties and other important factors into the assesment and that implies WRC 107/297, PD5500 App g etc etc.
Allowables loads are a two way street. They have to be specified and then they have to be designed to by the manufacturer, before they are of use.
It is easy to envisage a vessel, say 1000mm in diameter, with a design pressure of 10bar, that would only require ~4mm wall thickness for pressure retaining. Try applying a ten tonne axial force and 4.7tonne-m moments to that shell see what happens. [Hopefully any decent manufacturer would beef the wall thickness up and use re-pads around the nozzles to acheive reeasonable allowable loads.[