What test medium to verify no yaw or deflection from straight penetration?

[Naphtali]

What are better-to-best test media to shoot very long cast bullets (in this case .54-caliber 525-grain pointed flat nose in 1:48 twist) to verify the bullet does not yaw or deflect during penetration? I have been using dry New Yorker magazines 12 inches thick and duct-taped together. This extremely penetration resistant medium shows no deflection from straight.

FYI: Dry magazines are much more penetration resistant than wet ones. Dunno why. No bullet I've tested - jacketed SP, Barnes Triple Shock; heat treated WW+2 or air cooled, etc. - not one has penetrated more than 7.5 inches at 15 yards.

[wv109323]

No one has answered this so I will take a shot(pun). All bullets yaw to some small degree. The bullet while passing through the air and rotating causes some air pressure differential around the bullets diameter. This is caused by the friction of the bullet with the air. The best test for yaw would be to fire into a supported piece of white cardboard and examine the bullet hole for roundness. Many types of competition use a scoring template that has a circle of known diameter (.30 cal., .224 dia., .452 Dia.) and is over laid the bullet hole. This test is for a double hit. This assumes no two bullets would pass exactly through the same hole but you could also look for yaw using the template. You may find one in .54 caliber. Yaw should be looked for at the longest distance that you expect to use the bullet. As the bullet slows down in speed and rotation the bullet will become unstable at some point.
The straight line inertia of the bullet going forward will not change until forces act upon it to push it from a straight path. Some of those forces could be uneven expansion of the bullet nose thus upsetting the balance causing the bullet to tumble and striking a bone or harder/softer tissue( a body organ or through the stomach) again changing the forces acting on the bullet. The myth that the M-16 bullet could strike you in the leg and come out your head was brewed up by the NVA that was issued the M-16 before US soldiers used the rifle.
I don't think there is a better media to use to measure bullet penetration. The media just has to be consistent for all the testing. Ballistic gel is used because it closely resembles the density of the human body. The US Army in the past fired into dead pigs to test bullet penetration. There was also a test procedure where a structure held a 1" thick pine board, a 1" air space. a 1" thick pine board, a 1" air space and on and on. The results were how many pine boards the the bullet penetrated.
The wet magazines become softer. A wet sheet of paper is easier to poke your finger through than a dry one.
The bullet with the best penetration will be one that has no deformation, the sharpest point, and strikes the media the fastest. The best would be a steel core FMJ bullet. In the Marine Corp, the fox hole earthen walls was suppose to be 36" thick. That was suppose to be thick enough to stop any small arms fire.

[quilbilly]

I find soaked and compressed phone books to do very well. I even have put an 1/8" thick piece of plywood veneer one inch in to simulate a clipped rib. You need at least 20 inches of phone books. The good news in my neighborhood is that twice a year, huge stacks of phone books are left at our local post office where they welcome my taking a couple dozen at a time. I test at 40 yards. They compress nicely if you stack them horizontally and tie them together while, in my neighborhood, the rain soakes ands swells them after good storm or two. Use strong string as their expansion has a lot of power.

[fouronesix]

I find soaked and compressed phone books to do very well. I even have put an 1/8" thick piece of plywood veneer one inch in to simulate a clipped rib. You need at least 20 inches of phone books. The good news in my neighborhood is that twice a year, huge stacks of phone books are left at our local post office where they welcome my taking a couple dozen at a time. I test at 40 yards. They compress nicely if you stack them horizontally and tie them together while, in my neighborhood, the rain soakes ands swells them after good storm or two. Use strong string as their expansion has a lot of power.

That's the system I've found to be the most consistent, so the conditions can be duplicated for comparing various bullets. I second the recommendation for using nylon string to bundle- expansion will break weak string. I soak the bundles in tub of water overnight. For straight line penetration through bone I also use various thicknesses of OSB.

Acute (shallow) attack angles through heavy bone is where most deflection will be noted. Use some hard, material like "concrete" siding material to simulate heavy bone. Most bullets, no matter the shape or type, will not deflect much with a perpendicular (+/- 90') angle of attack. Usually the only time you'll see odd behavior is with small bullets at high vel impacts or if the bullet tears, deforms or fragments into long or irregular shards. Set the hard "bone" material in between the wet paper bundles a few inches behind the entry face and at an acute (shallow)angle. That will tell the story about straight penetration- after all it's the severe angles of penetration that cause the deflection problems... not the perpendicular ones.

Most common bullets (high power controlled expanding J bullets and cast bullets) will penetrate between about 10" and 18" of saturated, bundled phone books. Big, slow cast bullets, even a 69 cal Minié of pure lead traveling only 900 fps will penetrate up to 19". The deepest penetration I've gotten from 30 cal premium bullets with an impact vel of about 2200 fps has been 16-18". The deepest penetration I've gotten from a 416 cal copper cup nose solid @ about 1900-2000 fps impact vel has been 25" but that includes a bone simulation of 1/4" fibered concrete plate plus 7/16" OSB inserted 6" into the saturated phone book paper media. All bets are off when testing big copper monometal dangerous game bullets at +/- 2200 fps, spire point AP type rounds, etc..... so plan for at least 3-4 ft of test media if testing those specialized types.

[JimP.]

i use wet newspaper for testing, i had a 500 gr hardcast 45/70 round penetrate 36 inches of wet newspaper and i had to add another foot of wet newspaper and a cement brick to stop it. JimP.