Ten rounds.
Why did I stuff ten rounds into a empty case? Some people measure case capacity in Milliliters, I prefer to measure it in Longrifles. For comparison a .338 Laupa has a capacity of 3 LRs.
I admit it is not the most accurate method of gauging case capacity 
Here’s a follow-up thread from the father of the shooter
http://www.calguns.net/calgunforum/showthread.php?t=258508
0 
0About 40 years ago some friends of mine and I contemplated necking a .50BMG to take phonagraph needle…After many more beers, and a discussion about how many reduction dies, and cost, it was going to take, we decided to try the .22 route, but a few more beers later we decided that we could not get a receiver strong enough to withstand the pressure of a full .50BMG case of powder pushing a .22…So we had a few more beers!
Spiff
0 0Spiff, LOL
0 0How many can fit in a .50 BMG?????
0 0Lance, I did not have an empty .50 bmg case on hand
0 0You’re a lucky man Steve, CCI subsonics are my favorite but nobody around here reliably has them, hp or ball.
0 0Nice hollowpoints for .22LR. What are they?
0 0Dom, they are CCI subsonic HP.
0 0
About 40 years ago some friends of mine and I contemplated necking a .50BMG to take phonagraph needle…After many more beers, and a discussion about how many reduction dies, and cost, it was going to take, we decided to try the .22 route, but a few more beers later we decided that we could not get a receiver strong enough to withstand the pressure of a full .50BMG case of powder pushing a .22…So we had a few more beers!
Spiff
Spiff, LOL
Here’s a follow-up thread from the father of the shooter
http://www.calguns.net/calgunforum/showthread.php?t=258508
How many can fit in a .50 BMG?????
Lance, I did not have an empty .50 bmg case on hand
You’re a lucky man Steve, CCI subsonics are my favorite but nobody around here reliably has them, hp or ball.
Nice hollowpoints for .22LR. What are they?
Dom, they are CCI subsonic HP.