Thursday, January 31, 2013

Speer Gold Dot .357 Magnum 125 Grain Clear Gel Test

 
I initially planned to conduct this test and publish it right after January 1st, but for many reasons I'm running about a month behind the 2013 blog publication schedule I had planned out in my head.  If you follow the blog, then you know I've run quite a few ammunition tests in the last 12 months.  As I was putting together the Ammo Tests Index Page, I was really surprised by how many tests were published in 2012.  It was during this organization process that I suddenly realized that I had never established a terminal performance benchmark against which we could compare all other tested ammunition.  As my statistician friend Steve used to tell me, you can only say results are good if you let your listener know what you are comparing against. 

The 125 grain .357 Magnum cartridge fired from a 4" revolver has long been the high water mark for effective defensive pistol ammunition.  The 125 grain load must be a "full power" 357 Magnum loaded to levels achieving 1400+ feet per second velocity from a 4" barrel.  Regardless of whose terminal ballistics testing doctrine you subscribe to, there appears to be a loose consensus that for pistol ammunition, the 125 grain .357 Magnum is the most effective fight stopper.  I have no expertise in wound ballistics or human anatomy so I will go along with the opinions of the experts in this area.

I was lucky enough to find a box of Speer Gold Dot 125 Grain .357 Magnum during this latest rush on ammunition.  The specific load tested came in the consumer retail packaging of 20 rounds with a published muzzle velocity of 1450 ft. per second as tested in a 4" test barrel.  I wasn't able to locate a box of Remington Express R357M1 125 grain semi-jacketed hollow point that is generally revered by the experts, but I feel the bonded bullet of the Gold Dot is a worthy substitute and may prove to be a better comparison with the current class of commercial ammunition choices available to consumers. 

Test Pistol Specs:
Smith & Wesson 686 +  4" Barrel

Testing Protocol:
My testing process is pretty simple.  I take one shot at the end of a Clear Ballistics Gel block that measures approximately 6" x 6" x 16" and weighs approximately 16 lbs.  I take the test shot from 8 feet away and impact velocity is measured less than 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 bullet.  Immediately prior to shooting the block, I take a 5 shot velocity test over a ProChrono Digital chronograph.

Test Results:
The test results are summarized in the data sheet below along with a close up shot of the recovered bullet.


Video documentation of the entire test from range through bullet recovery is available below.  The high definition video is best viewed on YouTube, but you can also view it here.


My Thoughts on This Load:
Since we are considering this test our benchmark for terminal performance, let's recap the facts from the test instead of me sharing my thoughts as I usually do.

Velocity:
Published velocity for this load is 1450 feet per second.  We observed 1456 fps average velocity in our 5 shot sample and the tested shot registered 1407 fps.  There appears to be quite a spread in velocity in the 6 tested shots with a low of 1403 and a high of 1496.  This may be the fault of the test revolver as the cylinder to forcing cone gap may vary by chamber.  This may also be due to variation in powder charges between cartridges.  Just to satisfy my own curiosity, I weighed the 13 remaining rounds in the box with the following results.
Cart # Wt. in Grains
5 221.9
13 222.7
2 222.8
6 223.1
3 223.3
12 223.3
8 223.5
11 223.5
9 223.8
4 223.9
7 223.9
10 224.2
1 224.7
Total 2904.6
Avg. 223.4

In the table above the cartridge number is simply the designation for the sequence the cartridge went on the scale.  For each cartridge the weight in grains was recorded from the scale.  I then sorted the list by weight from low to high and the randomness of the cartridge number indicates no scale bias.  I was shocked to see nearly 3 grains of variation between the loads.  I understand that a single cartridge is a system of many components that can all vary in weight by small amounts, but this seems excessive and may well explain the velocity variation between the tested rounds if the weight difference is in the propellant components of the cartridge (primer and powder).

We've seen variation like this in past tests where the terminal tested shot will be either significantly slower or faster than the 5 shot average.  This makes me wonder if I should weigh cartridges before testing and test with cartridges that are close in weight, or just continue to select them from the box at random.  In my opinion, random selection is closer to actual reality so I'm leaning toward accepting the variance and simply calling out loads that have excessive spreads.

Expansion:
The average expansion of the recovered bullet was .601".  We can turn this into an expansion ratio by dividing the expanded average diameter by the unexpanded bullet diameter of .357".  The result of the math is an expansion ratio of 1.68.  This means the recovered bullet is 68% larger than the unexpanded bullet.  I've read that an expansion ratio of 1.5 or more is a desirable trait in a hollow point bullet so this load exceeds the expansion goal.  I will be adding the expansion ratio to the data sheet on all future tests.

Weight Retention:
Weight retention is a measure that we have to take on faith when we test.  Since we can't weigh the bullet before testing, we have to assume that the bullet weight is close to the grain weight shown on the box.  In reality, we can buy a box of bullets for use as reloading components and measure them one at a time on a scale and see some weight variance from bullet to bullet.  When I was reloading and using also using saboted pistol bullets in my muzzle loading rifle it was common to see small weight variances.

The recovered bullet from this test weighed 124.4 grains.  We can convert this to a weight retention percentage by dividing the recovered weight by the bullet weight published on the box.  In this case the weight retention percentage was 99.5%.  I will be adding the weight retention percentage to the data sheet on all future tests.

Penetration:
The benchmark minimum desired penetration depth, in bare gel, has generally been set at 12 inches.  From various readings on the subject of desired penetration depth for defensive ammunition, any penetration depth between 12 and 16 inches appears to be acceptable.  In our test, the recovered bullet came to rest 14.25 inches into the gel.  From the artifacts left in the gel we saw that the bullet actually penetrated a bit deeper, but was pushed back up with wound channel as the gel block compressed back to its normal state.  We see this "rebound effect" in all tests so we will continue to record the final resting location as the measure of penetration depth.  As observed in this test, this load falls right in the middle of desired penetration depth range of 12 to 16 inches.

Energy:   
Kinetic energy is a calculated value that is derived by taking half the resultant value of the bullet weight (mass) multiplied by the bullet speed (velocity) squared.  Let's skip the physics lesson and review what we saw in the test.  The calculated energy value for this test was 549 ft./lbs. of energy.  While this test may not have broken any records for penetration or expansion, it certainly dumped more energy into the gel block than any previous test.  I consider the energy measure to be a "nice to know" value, but I think it's more important to understand what that energy did to the gel block.

As I reviewed the wound channel in the video, I hope you picked up on my mention of the overall height of the wound channel.  It was more than an inch tall with much of that damage being caused by the gel stretching as it expanded to absorb the energy of the expanding bullet.  The wound channel was also quite long and ran for a full 9 inches before starting to taper off.

Wrap Up:
If you are still reading this, then you must be a kindred spirit with a shared curiosity for all things dealing with terminal ballistics.  I know I got a little "wordy" with this recap, but I thought it was important that we take a small step back and explain a bit more about the variables captured during the tests and why they are significant.  I appreciate your patience as I got through all that.

In the future you may find yourself reading a terminal ballistics test done on some new whiz bang ammunition that delivers great expansion and penetration.  You may want to reference back to this test and see if expansion and penetration were really better than the gold standard 125 grain .357 Magnum.  Remember, if someone tells you that terminal performance was good or even great, be sure to ask them "compared to what?"  If you do, you will make my statistician friend Steve very happy.





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. Final photo not appearing here or on 1911forum.

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    Replies
    1. Thanks for the heads up. Must have been a photo server problem. It looks fine now.

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  2. Thanks for doing your good work. It sure helps us sort out options and make good considered decisions.

    Mike I

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  3. Lesson: 125 gr .357 Mag is mean as hell, especially out of a decent barrel length.

    Not meant flippantly: that's a good lesson. It is good to test the conventional wisdom to see whether it is just hype or, as here, resoundingly confirmed.

    Your tests convince me to go with the 3.08" barrel version when I pick up a Ruger SP101 soon. (It will replace one that I idiotically sold a while back.) Three inch is still pretty easy to conceal, and that + 0.8" of barrel over the more common SP could make a difference.

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