Interesting concept, I've loaded sabots for a .30-30 lever action. Never could get very good accuracy, like 2" - 3" at 75 yds. Have also loaded sabots for a friends 7.62x54R Nagant bolt action. Only loaded 10 rds, we got groups around 2.5", but didn't really pursue the idea.
Some things to consider:
1) don't use sabots in any gun with a flash hidder or muzzle brake. The sabot can get stuck in the hidder/brake and cause an unsafe condition that could lead to a burst barrel.
2) It's hard to get good neck tension with a sabot. You can crimp the heck out of them but they still won't be very tight. In a semi-auto as the cartridge is stripped off the magazine and fed into the chamber the bullet can be pushed back into the case. This can cause a dangerous pressure increase. If the bullet is pushed to deep it might actually fall into the case. This could cause a squib load, and the sabot/bullet might get stuck in the barrel, the next bullet down the barrel could cause a buldged barrel or burst barrel. So, as you work up loads shoot the rifle and let the rifle strip a cartridge off the mag. Then manually eject the unfired cartridge from the chamber and check the OAL. Do this 10 - 15 times. If the length doesn't change then it should be okay to proceed.
3) If you use reloading software or data from wildcat cartridges remember you're shooting a .30 caliber rifle, not a .22-08. It doesn't become a .22 until the sabot leaves the barrel. Also, the sabot itself has weight (like 10 - 15 grs), be sure to include the weight of the sabot in your calculations.
4) If you chronograph you loads - watchout. The sabot will probably hit and damage your chrony. It can also cause the chrony to give false readings: 3500fps, 900fps, 3525fps, 910fps...... The first number is the bullet, the second number is the sabot.
5) Regular .308 powders will be way-way to slow. Faster powders like 4198, Reloader 7, and A2015 are more appropriate. Ask the sabot mfgr for starting loads.
6) Your FAL might turn into a single shot, though it has the advantage of a gas system that can be regulated. You'll probably have to open the gas valve up almost all the way to get it to cycle.
Go slow, be safe, have fun... sounds like an interesting project. -- Kernel