Some steps to get suppression values for each HMG:
1. Calculate how many "in-game" bullets that HMG is shooting at desired range - per second with reload, per second without reload, per burst (whatever you're interested in). You can use formulas from the
CoH2 Stats spreadsheet to help you understand how it's done.
2. Multiply the number of bullets by the suppression value of the HMG (for example, Ostheer MG42 generates 0.012 suppression per bullet)
3. Now you can easily calculate how much time or how many bursts it'll take for the HMG to suppress or pin a squad. For most squads (if not all, haven't checked) suppression threshold is 0.2 and pin threshold is 0.6. You just need to divide the threshold value by what you got in number 2 to get the time or number of bursts (depending on what you're calculating).
Keep in mind that after the squad gets suppressed, most of HMGs (again, haven't checked all of them) apply only half of their suppression values to the squad - unless I remember that stats wrong.
Another thing to keep in mind is that some HMGs have better AoE suppression than others (like MG42 has it better than Maxim).
On my site
www.coh2-stats.com you have "per burst" graphs for HMG suppression, just under the DPS graph (
for example this), as well as some basic suppression raw stats (under Raw Stats -> Suppression section).