The EM Force Field is a small shield that the user can set up. The deployer and their teammates can shoot through the shield on the concave side; however, when opponents shoot at or through it, the shield will simply absorb the damage. The shield keeps absorbing damage until it has run out of HP at which point, it disappears.
Upgrading the shield will increase its HP.
Guardian X-78 bullets and Stinger Launcher bullets can't go through the shield even if you should be able to according to the things listed above