I thought I'd perform a real-world experiment today.
First up was a round containing 2.0 grains of Titegroup fired into a stack of pieces of 3/4" exterior-grade plywood. After that went well, I dropped the charge to 1.5 grains. Result? Squib about 1/4" into the rifling, meaning about half the length of the bullet entered the rifling. The bullet pushed out easily with a few taps on a brass rod inserted from the muzzle. Finally, back to 2 grains of TG and an almost identical result to the first. The length of penetration on the second round was a bit longer because the path was angled downward a bit more than the first.
The report of the first and third rounds was very subdued -- I would say not that much louder than a 22LR Aguila Colibri, but louder. With my muffs on, I could not hear the squib at all. After removing the case and seeing no bullet still in the case, a quick poke with a brass rod from the muzzle confirmed the squib and, again, a couple of gentle hits to the end of the brass rod with a hammer pushed the bullet out into the chamber.
Because pictures are worth, in my case, a thousand words, below is a photo that explains everything. Bullets 1 (on top) and 3 (below) penetrated completely through 3 pieces of 3/4" exterior plywood and almost all the way through the 4th. The 5th piece was penetrated by the tip of the first shot's bullet deeply enough that I had to pry it off the 4th piece, which did not take much effort. Had the 5th piece not been there, I believe the the first round may have gone all the way through the 4th piece, but maybe not. I believe that the second shot would not have penetrated all the way through the 4th piece under any circumstances.
Again, these results are using 2.0 grains of Titegroup; a Campro 55 grain FMJ bullet having a pretty sharp tip; a .223 Wylde-caliber BCL MRX Bronco Howitzer bolt-action rifle having a 9.5" barrel. (The chamber being part of the stated barrel length, I estimate the length of the rifled part of the barrel at
roughly 9.5" minus 2" equals 7.5".) Shooting distance was close. (BTW, below the black direction line, and just to the left of the stack, you can make out a brass rod I stuck into the first piece of plywood. It goes all the way through the succeeding pieces, touching the back end of the protruding bullet.)
What do you 22LR, 22WMR, 223 Rem.-experienced folks estimate the speed of those two shots was, roughly speaking, before they touched the first piece of 3/4" plywood and then penetrated almost 4 of them?
In closing, I must say that, so far, I really like Titegroup. Powerful stuff.
I see no need to experiment with charges below 2.0 grains, nor do I still feel the need for a chronograph. A bullet travelling fast enough to penetrate almost 3" of exterior-grade plywood is going to have no problem "penetrating" 40 yards of air to hit a paper target. I won't be disturbing anyone at the range, either.
