Just ran a penetration test on water-filled milk jugs, with caps screwed on, and the 6 jugs taped together with two wraps of duct tape. Range from muzzle to first jug was 10 feet. Temp was about 82 degrees. No attempt was made to tilt guns to seat powder against either primer or bullet.
#1: Colt Detective Special .38 SPL, 2" bbl, with 200g Mt. Baldy LSWC-K, meplat .280 (I think) seated deep and crimped over front shoulder, with 3.4g Win231. (This load and gun previously chrono'ed at 718 fps, thereby trying to ensure similarity to original factory ballistics of 770 fps from 6" bbl. It is modified from "Mikey's load" of 3.8g of the same powder.)
RESULTS: penetrated all 6 jugs and struck nose-first into a 2" x 12" placed behind the last jug, knocking a hole in the board up to the bullet shoulder, then falling out onto the ground while knocking down the 15" long board. Bullet path was arrow-straight, exiting through the tape on the back side of the sixth jug at same relative location as it struck the first jug. All caps remained intact. First two jugs failed at the circular "dimple" molded in the side; all others bulged the dimple outward without causing it to fail. After impact, the row of taped-together jugs toppled over and fell off the two 2"x4" boards I'd placed them upon.
#2: S&W Mod. 30-1, .32 S&W Long, 2" bbl., with 115-grain Hunter's Supply LFP .313 bullet, meplat .220 (I think), seated to crimp groove, with 2.8g Win 231. (This load is based on Ed Harris's loads recommended for strong, modern S&W heat-treated revolvers, keeping sample average at/below 850 fps from 4" bbl. From my 2" bbl., this load chrono's at 770 fps.)
RESULTS: penetrated all 6 jugs and struck nose-first into a 2" x 12" placed behind the last jug, knocking a shallow 1/8" dent in the board, then falling out onto the ground without knocking down the 15" long board. Bullet path was straight until it exited the 5th jug and entered the 6th, deviating about 2" by the time it exited the last jug. This may or may not have been a result of me failing to align my jugs & the shot as exactly as I did with the .38. After impact, the jugs remained atop the two 2"x4" boards they were placed upon. Perhaps that was due to lesser impact force, or perhaps it was because I had shimmed the rather unstable boards before this shot.
Using the "Ballisticians' Corner" formulas provided at Beartooth Bullets website, here is additional info about these loads:
1. Permanent Wound Channel (vel x meplat): .38 is .503"; .32 is .424"
2. Relative Penetration Index (wt. x meplat): .38 is 49.6; .32 is 33.94
3. Thornily Relative Stopping Power (wt. x diameter x vel.): .38 is 35; .32 is 20
4. Taylor Knock-out Power (wt. x vel. x diameter): .38 is 7; .32 is 4.
Also, I calculated the foot-pounds of energy as 229 ft-lbs. for this .38 load, and 151 ft-lbs. for this .32 load.
After we drink some more milk, I'll try the same tests with some other loads. Happy shooting!