If one wants to simulate bone for bullet testing, I would recommend a thoroughly water soaked phone book which is about 1 inch thick with water jugs behind it. Live bone is 75% water and cellulose (paper) cell structure is similar to bone cell structure except for the calcium content. I have used 4"x4", 4 foot Douglas fir studs for .338 and .375 Ouch & Ouch bullet testing. I used them both crossway and length wise with Nosler Partitions. I shot a bunch of calibers from .270 Winc to .375 H&H, including .300 H&H and .338 WM. IMHO, wood is not the ideal medium because of density variation between dry and non-cured wood and splitting which tells you nothing. If dry, it almost always splits, even lengthwise with these two calibers which gives you variable data in a too variable medium. BTW, the .338 250 gr Partiton and 270 gr, .375 Partition were the only bullets to go 4 feet through fir studs in my test, all of the other calibers failed! Add in the inconsistancies of the Berger 215 bullet for penetration and for me, it is impossible to infer any conclusion from this test except that Bergers are not the best elk bullets.
The National Rifleman had a test years ago (late 1960's?) in an article where they used hardwood boards (3/4 inch thick) with 16 inch ballistic gel blocks behind the slats. They also splash covered the boards with Alaskan river mud to simulate a wet muddy brown bear (tough test!). They tested everything from a .308, 180 grain to the .375 H&H 300 grain, all factory loads, including .44 Magnum revolver and 12 gauge shotgun with 1 ounce slugs. This test should be repeated now with premium bullets because the results would be much different than they were with 1960's CoreLokt performance. However I think that the test was a fair one despite all of the lighter caliber bullets failing to penetrate the gel block. Only the .338 WM, 250 gr and .375 H&H, 270 gr went through the test meduim, end to end.
I think that uncured oak, ash or rock maple boards with 16 inch ballistic gel would be a super test medium to simulate elk ribs and chest cavity material. However, I would use Nosler, Woodleigh, Swift A-Frame, Trophy Bonded Bear Claw and Barnes TSX etc, bullets for this test. Even a 1' wet phone book and water jugs would be better than 4x4's as a test medium, FWIW.
The issue that I had in my tests, with fir studs, was that high velocity, small caliber bullets did not penetrate fully through the wood. These smaller caliber bullets did not have high enough inertia numbers and were too high velocity. In the NRA test, the .300 Win Mag failed the penetration test worse than the .308 did. This however probably has more to do with poor bullet design of the 1960's.