I fired one done up by a Civie Gunsmith for the Navy on a M60E3 receiver. He used the short, light M60E3 Navy barrel, E3 front grip and light E3 stock but he added a E4 top cover with the 1913 rail. Whole thing was under 17 pounds unloaded and he ran an Aimpoint on the top cover with a 100 round CapCo plastic drum from the 1990's. Very light and easy to shoot and could be shouldered fast!
For giggles he put a Surefire 7.62MG suppressor on a longer, lightweight E3 barrel with the front sight moved back and it was actually very accurate and not bad from behind the gun - but it made a racket on either side. He popped another light long barrel with a semi custom AAC SCAR Heavy suppressor and although it was subjectively more quiet than the Surefire 7.62MG, it did blow back a bunch of gas from the ejection port. The Surefire did show signs of ALOT of gas migrating back through the rear mount - since the carbon caked all around the rear mount interface. Still nice to shoot some suppressed belt feds. I missed out on shooting the new SIG M240 suppressor on a M240N, but I did get behind a test AAC M240 suppressor and it functioned fine - with the same gas blow back as in all the models.
Sadly those M60's got sent back to Crane for disposal (?) and the barrels were slated for demil/disposal - thus the Knob Creek style shoot out with all the different suppressors. All the armorers got to shoot them and diagnose the issues or possible issues then one to another weps system - but I got to throw a couple 100 round belts down range without tracers - then we loaded 1000 rounds of all of the collected tracers through a M134D in a ring mount. That was the most fun of all, especially in the slow fire setting/motor drive.
Nice work on that SEAL M60! Those rubber boots are very hard to find.