One more penetration test.

[Nomadic Pirate]

Thanks,

the .30 is at 90 FPE

[Nomadic Pirate]

Well, I have a lot of untouched left over material for more testing  LOL

[subscriber]

About MDF VS Plywood:

Penetration is not just blocked by strong materials, but by heavy ones that generate a "friction cone" once penetration starts.  Think about how effective sand is at stopping projectiles - and it has negligible bulk strength.  Only mass and friction.

The nature of MDF fiber is to form an expanding cone in front of a penetrating projectile.  The the deeper the projectile penetrates, the greater the mass of material the projectile has to push ahead of itself, in a much greater than linear progression.  Ditto for the total area that sees friction within the material.  Hence MDF is harder to penetrate than plywood, despite being weaker when "bend tested".

Mass can also aid penetration of strong materials:
Think of shooting at a 1" steel disc that is only .02" thick (like a thin steel coin, if you will), using an airgun projectile travelling at 800 FPS.  Those discs are so light that they are thrown out of the way, rather than penetrated, if you stick just one edge lightly into clay.  Now, back that same little "coin" fully with a pound of clay so it can't move easily, and see how easy it is to penetrate. 

[Rallyshark]

Well, I have a lot of untouched left over material for more testing  LOL

Do it with slugs in the .25 and .30!  I'm curious to see if they'll make it through.  I suspect they will, but I could be wrong? 

About MDF VS Plywood:

Penetration is not just blocked by strong materials, but by heavy ones that generate a "friction cone" once penetration starts.  Think about how effective sand is at stopping projectiles - and it has negligible bulk strength.  Only mass and friction.

The nature of MDF fiber is to form an expanding cone in front of a penetrating projectile.  The the deeper the projectile penetrates, the greater the mass of material the projectile has to push ahead of itself, in a much greater than linear progression.  Ditto for the total area that sees friction within the material.  Hence MDY is harder to penetrate than plywood, despite being weaker when "bend tested".

Mass can also aid penetration of strong materials:
Think of shooting at a 1" steel disc that is only .02" thick (like a thin steel coin, if you will), using an airgun projectile travelling at 800 FPS.  Those discs are so light that they are thrown out of the way, rather than penetrated, if you stick just one edge lightly into clay.  Now, back that same little "coin" fully with a pound of clay so it can't move easily, and see how easy it is to penetrate. 

Makes perfect sense!

[Nomadic Pirate]

OK, I'm gonna try shoot .30 and .25 slugs,......my bet, they aren't gonna get through

[subscriber]

OK, I'm gonna try shoot .30 and .25 slugs,......my bet, they aren't gonna get through

They might, if they are "solids"...

[Nomadic Pirate]

OK, I'm gonna try shoot .30 and .25 slugs,......my bet, they aren't gonna get through

They might, if they are "solids"...

Yes I have solids both in .25 and .30

But going by How little penetration 200gr and 190gr solid slug had I guess not

[Horatio]

Test seems quite scientifically structured to eliminate whatever variables you can.

But exactly how are you gonna measure penetration depth (or anything else) with that tape measure? Belongs in a museum!

You could just poke a section of rod or coat hanger into the hole. Mark what’s flush. Measure between Mark and tip.

[subscriber]

That tells you how deep the projectile base is; but not how deep the nose is...

Test seems quite scientifically structured to eliminate whatever variables you can.

But exactly how are you gonna measure penetration depth (or anything else) with that tape measure? Belongs in a museum!

You could just poke a section of rod or coat hanger into the hole. Mark what’s flush. Measure between Mark and tip.

[subscriber]

Yes I have solids both in .25 and .30

But going by How little penetration 200gr and 190gr solid slug had I guess not

Round nose, heavy for caliber .25 and .30 should do well.  Especially if made from lead with 3+% antimony.

[mrbulk]

Fascinating, at first I did not think you could differentiate penetration depths because of the density of MDF. But brittleness and being less resistive to flex proved otherwise.

[Horatio]

I've never shot MDF but I use scrap 3/4 plywood to stop pellets when I am getting velocity readings on my 25 caliber Avenger.  It blows through it with the regulator set to 1500 psi.  fpe is 33 to 39 depending on the pellet weight.  Velocity goes from a little over 700 fps to over 850 depending on pellet mass.  I have a second piece behind the first and it just gets dented typically.  I will turn up the regulator eventually but I am having fun with it at the low regulator setting.  It can be raised as high as 2900 psi on this rifle. 

My main hobby is woodworking.  I don't like MDF because the dust it makes is terribly nasty.  It is not stronger than plywood, it is weaker.  It is also easily damaged by water.  The Brits talk about water resistant MDF but I've never seen it.  For shelving purposes we look at the modulus of elasticity.  Hardwood is strongest, has the highest modulus, softwood is next, then plywood, then particle board, then MDF.  I don't know however, if that translates to penetration but I tend to think it does.  If I had any laying around I would shoot it and find out.  I agree, however, that MDF will be more consistent than wood or even plywood.  Shooting it may be a good thing to do with MDF.

That’s what I was thinking. Go ahead and shoot it. Sounds like an awesome penetration test.

But as far as a building material? Is Hawaii humid? Wherever MDF was used. Check back in a few years and see where it’s bubbling and coming apart.

Both the wood dust and the binding agent seem to absorb up water.

[Horatio]

That tells you how deep the projectile base is; but not how deep the nose is...

Test seems quite scientifically structured to eliminate whatever variables you can.

But exactly how are you gonna measure penetration depth (or anything else) with that tape measure? Belongs in a museum!

You could just poke a section of rod or coat hanger into the hole. Mark what’s flush. Measure between Mark and tip.

True. But we know the projectile won’t be any longer than new. So you have a good enough measurement.

[subscriber]

True. But we know the projectile won’t be any longer than new. So you have a good enough measurement.

Don't lose sight of the point of this exercise:  If we want to be sure that a projectile has passed through an animal's skull, we want to know where the projectile's nose stopped, not its base.

All moot, if the projectile base makes it all the way through.

It is all a matter of how "good enough" is defined.  To me, good enough means the projectile impacts the far-side of the skull, after blowing through the nearside.  So, measuring partial penetration of a wood substitute, used as a bone substitute is a little dicey.

[Horatio]

I've never shot MDF but I use scrap 3/4 plywood to stop pellets when I am getting velocity readings on my 25 caliber Avenger.  It blows through it with the regulator set to 1500 psi.  fpe is 33 to 39 depending on the pellet weight.  Velocity goes from a little over 700 fps to over 850 depending on pellet mass.  I have a second piece behind the first and it just gets dented typically.  I will turn up the regulator eventually but I am having fun with it at the low regulator setting.  It can be raised as high as 2900 psi on this rifle. 

My main hobby is woodworking.  I don't like MDF because the dust it makes is terribly nasty.  It is not stronger than plywood, it is weaker.  It is also easily damaged by water.  The Brits talk about water resistant MDF but I've never seen it.  For shelving purposes we look at the modulus of elasticity.  Hardwood is strongest, has the highest modulus, softwood is next, then plywood, then particle board, then MDF.  I don't know however, if that translates to penetration but I tend to think it does.  If I had any laying around I would shoot it and find out.  I agree, however, that MDF will be more consistent than wood or even plywood.  Shooting it may be a good thing to do with MDF. 

Well data says the opposite

My .25 and .30 Blow through quality 3/4" Birch Plywood and keep going for some time into other mediums, both didn't even make it out of the MDF

That would make sense. It’s dense. And it isn’t connected through the grain like real wood.

[Nomadic Pirate]

One more point I like to make :

I'm quite confident if the MDF board was standing alone all projectiles would have made it through, but having those layers pressed behind the board is an all different cup of tea since they offer a lot of resistance so it's much harder to blow to the other side.

[Horatio]

It’s a cool test.

I think all projectiles would penetrate a skull, depending on angle of impact more or less.

If I ever get to pop the skull of the animal I PMd you about, I’ll let you know.

[Nomadic Pirate]

It’s a cool test.

I think all projectiles would penetrate a skull, depending on angle of impact more or less.

If I ever get to pop the skull of the animal I PMd you about, I’ll let you know.

Of course they will ALL penetrate the skull of a big game animal that has been confirmed and re-confirmed many a time,
 but that was not the goal of the exercise, the goal was to see the difference between the .357 ammo,...the .30 and .25 where just thrown in for kicks

Unfortunately the MDF board proved to strong and there was no real separation,.....I will probably repeat the same test without the MDF

[smythsg]

Very interesting results Manny! Now I have to get me some 3/4 MDF to test with my Condor and my Escape. I can crank up the fpe with those two and see if I can penetrate. I don't remember seeing it, but I assume you were shooting at 20 yards?

[Nomadic Pirate]

Correct.

Today I will take some shots with the .25 at the board standing alone and I'll predict easy blow out da back

The compressing of layers at the back of the board makes a world of difference.