Your guess is as good or better than mine. If it would work, i think the results would be less erratic than what i experienced today. What about putting them practice plastic bullet into a sabot?

Here is a copy of what Speer write about their plastic priactice bullet.



Product Information

Do you want to get a little handgun practice at times you can't get to the range? Don't have a heavy-duty backstop in the garage? SPEER Plastic Training Components are the prescription you need for short-range practice. This isn't loaded ammo. We make the bullets and cases--you supply the power. A standard large pistol primer provides all the power needed to propel the reusable bullets at velocities between 300 and 400 ft/sec. Cases are reusable, too. You don't even need reloading equipment to assemble Speer practice ammo. The case/bullet system is available for 38/357 and 44 caliber revolvers. For the 45 Auto, use our bullet and a standard 45 Auto brass case with a drilled-out flash hole. A backstop for these bullets can be quickly built from a cardboard box and carpet scraps. Bullets and cases are sold separately so you can replace lost or damaged bullets. SAFETY FIRST: Never use propellant when loading Plastic Training components. Treat the resulting ammunition with the same respect given conventional ammunition; velocity is high enough to injure the skin. Use only in well-ventilated areas. Brush the bore every 12-18 shots to prevent accumulation of primer residue.