Wednesday, November 28, 2012

Clear Gel Terminal Testing Sellier & Bellot 32 Auto 73 Grain FMJ


I do my best to keep the blog free of politics so I won't go into the reasons why the outcome of the latest Presidential Election didn't surprise me.  Remembering what happened to ammunition supplies after the previous election, I decided to proactively track down a few extra boxes of carry ammo for any pistol that might end up in my pocket or on my hip in the next few years.  Prior to putting in my order, I decided to do a clear gel test on my favorite FMJ and JHP ammo for the P-32 that will end up in my pocket occasionally. 

Folks that carry pistols chambered for .32 AUTO or .32 ACP seem to fall into two camps.  The FMJ camp and the JHP camp.  I've done my homework, through previous terminal tests, so I know which .32 ACP JHPs will actually expand and those that won't.  What I didn't know was the penetration capability of FMJ bullets traveling at velocities attained when launched from a short barrel semi-auto.  Rather than guess, I decided it was time for a test with the new clear gel test medium I have been using.  I also hoped to get some additional insight into bullet tumbling that some folks mention as they expound on the virtues of .32 AUTO FMJ ammunition.

Pistol Specs:
Kel-Tec P-32 2.7" Barrel


Testing Protocol:
My testing process is pretty simple.  I take one shot at the end of a Clear Ballistics Gel block.  I take the shot from 8 feet away and impact velocity is measured 2 inches away from the block.  Clear Ballistics Gel is calibrated to 10% ballistics gel density.  I shoot the block at the range and then bring it home to analyze the block and recover the bullets.  Immediately prior to the terminal test, I shoot a five shot velocity test string from 8 feet over a Competition Electronics ProChrono Digital chronograph.


The video below documents my entire test from range testing to bullet recovery.
Direct Link to Video on YouTube


My Thoughts:
My initial thoughts were that I really NEED a professional high speed camera with HD resolution so I can actually see the bullet tumble as it travels through the gel block.  Reviewing my own amateur high speed footage, and trying to match that up with the artifacts left in the gel block, has been really interesting for the ballistics geek in me.  Allow me to put forth my theory.

In the picture below you can see the start of a typical wound channel and stretch cavity.  With a FMJ bullet, I didn't expect to see much more than a temporary stretch cavity of uniform height through the first several inches of travel until the bullet slowed.  What we got was a uniform stretch cavity for about 3 inches, then an expansion bubble, followed by a series of waves.  Finally the stretch cavity settles down again into a normal pattern.

My theory is the expansion bubble was caused by the bullet tumbling 180 degrees.  The temporarily larger bullet surface area, caused by tumbling, registered as a temporarily larger stretch cavity.  I believe the wave pattern immediately after the bubble was caused by the cupped base of the bullet as it progressed base-first down the wound channel.  Energy loss was so great at this point, the remainder of the wound channel actually appears to be normal. 
From previous tests HERE we know the Sellier & Bellot FMJ ammunition used in this test is the fastest and heaviest .32 ACP ammo available in a standard pressure loading.  There may be other more exotic (aka expensive) boutique ammo brands that have a heavier bullet or faster velocity, but they are tagged as .32 ACP +P.  Since there is no SAAMI specification for .32 ACP +P  ammo, it's buyer beware when using loads tagged as .32 ACP +P or .32 AUTO +P.  One thing I did learn was that my fear of gross over-penetration with .32 ACP FMJ ammunition was pretty much baseless.  Bare gel is an optimum test bed.  Real world exterior and interior barriers will all do their part to leech energy from the bullet as it travels.  If I was going to experience over-penetration with FMJ ammunition, this one should have over-penetrated.

The 2.5" to 3" of lateral travel that I mentioned in the recovery portion of the video was interesting, but I've seen similar things happen to high velocity JHP bullets that fully expand and still have velocity behind them.  My theory here is that once the bullet turned 180 degrees, it was weight forward and most probably turned a few degrees less than a perfect 180.  This caused the bullet to track in the direction that the bullet base was facing.

I stop short of making recommendations, but I will say that the FMJ camp sure does look a whole lot better to me after this test.


Disclaimer....This test should not be considered an endorsement or recommendation for the product(s) tested.  All tests represent actual performance in ballistics testing media.  Terminal performance in all other media will show different results.  It is up to each individual to make their own personal decision on which specific ammunition to use for their needs.  It's also critically important to test any ammo in YOUR SPECIFIC FIREARM before relying on it for any purpose.

Ammunition labeled as +P or +P+ should only be used in firearms that have been certified by the manufacturer as safe for the additional pressures generated by these ammunition types.

5 comments:

  1. As FYI, chronograph results of single, 5-shot strings of various .32 ACP FMJ ammos, all fired from my Beretta Model 3032 INOX with 2.4" barrel:

    R-P 71 FMJ 785 fps
    W-W 71 FMJ 847 fps
    Magtech 71 FMJ 806 fps
    Fiocchi 73 FMJ 845 fps
    RWS 73 FMJ 959 fps
    Sellier& Bellot 73 FMJ 938 fps
    Norma 73 FMJ 894 fps
    Geco WW2 steel cased 73 FMJ 907 fps
    Handload, Magtech 71 FMJ, 2.5 Bullseye 910 fps.

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    1. Thanks for the info.

      FYI for anyone that that reads the comment above. Please consult a published reloading manual for reloading recipes. Typos can and do happen so it's always best to verify any reloading recipes you pick up on the internet against a published reloading manual.

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  2. Do you have data on JHPs? I've had trouble with FTE and FTF using JHP in my P 32 which I attribute to the lighter bullet.

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    Replies
    1. I've done a few tests. You can find them on this page listing all my tests. http://mousegunaddict.blogspot.com/p/ammo-tests.html There is a page tab at the top of the blog called Ammo Tests, you can also click on that to get to the listing.

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  3. European .32 ACP, or 7.65mm Browning, as they call it, is loaded to quite a bit higher pressure than US commercial ammo. Pt Max. or maximum average chamber pressure listed by the CIP is 1600 bar, which equates to about 23,200psi.

    See http://www.cip-bobp.org/homologation/en/tdcc_public?page=1&cartridge_type_id=4

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