It will only work once or twice as the pigs will learn.
Truer words never penned. They will learn, and fast, that the feeder is a death trap.
However, and depending on the proximity of the stands to the feeder, you may, I repeat may be able to shoot them with a rimfire 22 LR and not startle them too badly into running off into the woods never to return.
Before you condemn me, please let me explain.
Large(r) caliber rifle fire at close range (DRT range from the pigs perspective), will send them running for cover and much farther than that. They may go nocturnal and not been seen in daylight again for a long time. Nothing certain on that though. Not wanting to bank on them...
In my scenario:
1. stands placed within 25 yards of feeder,
2. accurate rimfire rifle,
3. steady rest,
4. 22LR minimum caliber
5. full frontal head shots ONLY
Shoot it in the middle of the imaginary "X" between the eyes and ears. IT WILL GO DOWN. Then when the rest of its buddies get over the "startle effect" they will settle down and continue eating corn right beside their now dead buddy. Shoot another one. Same way. Continue until they get wise and depart; you are out of bullets; or you kill all that are there at the time.
Perhaps even have your BIL shoot a rimfire a few times while he is spreading the feed. That'll condition them a bit.
Works for me.
The rimfire, for some, is just too small. In that case, a large caliber rifle is also a good way to go.
Good luck. Kill them ALL. There is no "End of Line" when it come to killing pigs.