I've got a .22 blank revolver, but a box of 50 blanks is pretty costly. I also have an old 12 ga single shot, but poppers are for the rich and famous. I bought a bunch of misc gun stuff out of an estate. In this pile was a bunch of old .223/5.6 blanks. Some of them looked gnarly, so I stuck them in my bolt .223 rifle, and pop they went. The sound was pretty good.
Here's my thought. Find a cheap/inexpensive break open single shot like a H&R in .223. Should costs +/- $150. If it is too unwieldy, cut the barrel down to a shorter but legal length. Then go buy a bucket of .223 blanks. 500-1000 should cost about $10. Heck, some guys would give them away to not have to carry them back to one more gun show.
If a guy is doing lots of training w/ poppers or blanks the pay off would occur the first year. Back when I was training full time it was nothing to go through 20 boxes of blanks and 5 or more boxes of poppers a year.
Anyways, just thought on saving a buck or two,