Tired of paying $12 for 100 .25 ACP jacketed bullets for reloading, if you can even find them? Try this cheap, plinking alternative:

Resize a case and ensure it does not exceed the maximum length of .610 inch. If it does, carefully use a very fine file to reduce its length. Few case trimmers can accommodate the tiny .25 ACP. Though Lee makes .25 ACP reloading dies, it does not make a case trimmer pilot for this Lilliputian case.

Bell the .25 ACP case mouth to avoid shaving the lead ball when it's seated. If your dies do not bell, insert a .223 case into the .25 ACP case mouth and tap the .223 case lightly with a hammer a few times. The shoulder of the .223 case will easily bell the mouth of the .25 ACP case.

Prime a resized case with a standard small pistol primer. There is no need to use a magnum primer.

Add powder (detailed instructions below).

Seat a Buckshot No. 3 lead ball up to its midpoint into the case. The typical No. 3 buckshot ball weighs about 23 grains and is .250 inch in diameter. This is a good fit in the .25 Auto bore, which is nominally .251 inch.

Firmly crimp the case around the seated ball.

Turn the loaded cartridge over and dip the ball, up to the case mouth, in Lee Liquid Alox. A screw-top bottle cap works well as a lubricant container for dipping the loaded balls. If the lubricant begins to stiffen, add a drop of Mineral Spirits and mix well with a toothpick to thin it.

The seated lead ball lubricated, stand the cartridge on its base in the open air and allow the lubricant to dry overnight.

This load is mild, functions most pistols, shoots to about the same point of aim as the 50-grain factory load and is accurate. Not much power to it, but it’s no toy. It will penetrate both sides of a can at 20 feet.

For the powder charge, start with 1.0 (one) grain of Bullseye and increase the charge 0.1 (one-tenth of a grain). Stop when reliable functioning is attained.
Most guns will operate well with 1.3 grains of Bullseye.
Be very careful when charging the .25 Auto with powder, as only small powder charges are used and a double-charge can be easily overlooked. Look down into each charged case with a strong penlight to spot a double charge.
A double charge of Bullseye would likely damage the pistol, and may injure the shooter.

I have not tried other powders but similarly fast pistol powders should work. Or not. You’re on your own when it comes to experimentation.
Using other powders, start the No. 3 buckshot load with a reloading manual’s suggested starting load for the 50 gr. jacketed bullet. This will ensure a mild starting load from which you can work up, if necessary. Remember, you’re seeking reliable functioning with this load, not velocity. If your first load is reliable and accurate, why go on?

The light lubricant on the ball is important. Without it, leading will occur quickly. If your bore does lead, run a dry, bronze brush through it a few times.

This is a surprisingly accurate load.
At seven yards, from a benchrest, I've placed six of these lead balls into groups of 1.5 to 2 inches. This was with a pre-war Sauer & Sohn Model 1928 of outstanding quality but very small in my hands. Inexpensive, average or poor quality pistols may not be as accurate. Most .25 ACP pistols have rudimentary sights, so consistent accuracy can be difficult.
I wish Ruger would chamber their Mark II for .25 ACP, with bull barrel and adjustable sights. I think people would be amazed at this cartridge's accuracy.

This No. 3 buckshot load is fun. It would be handy for farmers and ranchers who encounter rats in their barn but don't want big holes in structures. It is strictly for plinking and practice and should never be carried for self defense.

There are about 300 lead balls to a pound. Buckshot is usually sold in 5-pound containers, so you can buy about 1,500 No. 3 buckshot balls for about $20.
Quite a savings over the jacketed bullet price, eh?