Thursday, February 7, 2013

Speer Gold Dot 357 Magnum 158 Grain Clear Gel Test

If you have an evil streak in you, drop by a gun related forum of your choice and ask if 125 or 158 grain bullets are better for 357 Magnum personal defense loads.  Let that question hang out on the forum for a few days and come back and read what people post.  If you don't want to wait, you can always google "125 or 158 grain 357 magnum for personal defense" and click through the resultant links to various forums where this question has been previously discussed.  It appears to be quite a controversial topic with proponents in both the 125 and 158 camps.  I see the merits in the arguments coming from both sides of the discussion, but wanted to do my own test and see if one stood out as the better choice of the two.

Last Thursday I published the Speer Gold Dot 125 Grain 357 Magnum test results.  You can see a recap of the Bare Gel and Stress Test by clicking on the links.  This week we're taking a look at the 158 Grain version of Gold Dot 357 Magnum load that was tested on the same day and in the same gel block as the 125 grain load.

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:

Published velocity for this load is 1235 feet per second when fired in a 4inch test barrel.  Even though the load was tested in a 4 inch barrel, we did not meet the published velocity.  As we saw in the video, that might be a blessing with this load since penetration was excessive and may have been even deeper with another 50 feet per second on top of our tested velocity.

The average expansion of the recovered bullet was .515".  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 1.44.  This means the recovered bullet is 44% larger than the unexpanded bullet.  On the surface that expansion ratio doesn't appear to be very impressive, but if you look at the recovered round you will see that expansion was complete and the trademark Gold Dot is clearly visible at the bottom center of the hollow point cavity.

I took a closer look at the 125 grain and 158 grain Gold Dot bullets loaded in these 357 rounds.  Aside from the 158 being longer overall than the 125, the noses of the bullets have very different shapes.  I also think the jacket and lead hardness may different.  The 125 grain petals peeled back all the way to the crimping groove or canalure of the bullet, while the 158 grain petals stopped well short of the canalure.  This difference and the fact we see the "gold dots" on the top of each recovered bullet lead me to believe both the 125 and 158 grain bullets expanded exactly as they were designed to expand. 

Weight Retention:
The recovered bullet from this test weighed 157.9 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 99.9%.  Weight retention was excellent as we would expect from the Gold Dot bonded bullet.

I'm really glad I decided to add a half block behind the normal 16" block for this test.  As we saw in the recovery portion of the test video, penetration was an incredibly deep 23 inches.  Luckily we caught the bullet in the block and were able to get an exact measurement of the penetration depth.     

As we discussed in the 125 grain review, energy is a calculated value that offers a comparison point from one load to another.  I have noticed that the hollow point rounds carrying the most energy into the block tend to create the largest temporary stretch cavities.  How much permanent damage is caused the temporary stretch cavity is another highly debated topic on the gun forums.  I will say that the wound channel artifacts left in the block showed a smaller, but equally long wound channel as compared to the 125 grain load.

Wrap Up:
I found it very insightful to see what a difference 28 grains of bullet weight can make between the previously tested 125 grain and the 158 grain load featured in this test.  While both bullets share the Gold Dot name, I have to believe they are constructed differently and may even be intended for different purposes.  This load definitely sets the standard for rapid and controlled expansion with very, very deep penetration.    

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.

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