The VA has a disability evaluation process that is similar to, but not identical to that used by Social Security. Social Security judges are not required to honor a VA determination of disability but my experience has been that a veteran with a 100% disability rating usually stands a good chance at winning SSDI.
Unlike Social Security, however, veterans can recover less than 100% VA disability. A vet with, for example, a 20% disability usually will not see much benefit when he applies for Social Security disability.
This past March, SSA announced a new policy that will provide for expedited claims processing for disabled veterans who have been awarded 100% permanent and total disability from the VA. If you have such an award, you or your attorney needs to provide SSA with a copy of your 100% P&T compensation rating and your Notification letter.
SSA’s new policy does not mean that 100% P&T vets will automatically win SSD. It does mean that their cases get moved to the front of the line.