I recently made the following post regarding indoor/backyard loads using round balls in another thread, but it seems to fit here, too, so here you go.
"... I found my old note book from the early 70's in which I recorded my experiments using a 20" barrel [Rem 600] and found the following data for round ball basement loads in 308. Shooting into phone books,
1g of BE penetrated 500 pages and was very quiet
1.5g BE penetrated 900 pages and was still quiet
I then held the rifle up to position the powder against the primer and
1.5g BE penetrated 3/4" plywood plus 970 pages of phone book.
2.0g BE penetrated 3/4" plywood plus 1000 pages of phone book, the ball being deformed.
At the range, 25 yards,
1g BE not accurate
1.4g BE went into 1.5"
1.7g BE went into 1.5"
2.0g BE went into 1.375"
I then later chronographed not the above loads, but rather
1.5g 700X which clocked 675fps.
None of this is to be taken as gospel as the total shots fired were few, but it is an indication of what can be expected. A
longer barrel would call for slightly higher charges I guess.
In any case, a 30 cal 43g rb at 675fps whizzng across your basement is not to be sneezed at. Do not underestimate the potential for damage or injury here. In fact, I strongly recommend you not try any of this [indoors].
Having said that, I also worked up (down) basement loads in my .222 using pulled [or possibly snipped] .22 long rifle bullets, and then later wad cutters from a home made mold. [1/4 to 3/8" aluminum plate drilled straight through, pivoting bottom plate.] .3g of PB (yes, 0.3) was the ticket there. Later I tried 22cal pellets with some success. But again, none of this is really practical. Lots of fun maybe, but not practical. Like Christmas trees, all of these guns and calibers are a lot bigger indoors than they seem outdoors."