Saturday, February 2, 2013

Speer Gold Dot .357 Magnum 125 Grain Stress Test

This is the first completed stress test using my new stress test barrier in front of the gel block.  The history and complete disclosure of what materials go into the stress test barrier can be found HERE so I won't go into it again in this article.  It was important to me that this load should be the first one tested in the barrier so it could serve as a performance benchmark for all subsequent tests.

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.  

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.

Stress tests include an additional barrier of 5/6 ounce tooling leather and 2 layers of medium weight denim in front of the gel block.

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 stress test terminal performance, let's recap the facts from the test instead of me sharing my thoughts as I usually do.

The test shot registered very low velocity.  I'm going to discard the measurement because I think the barrier panel may have interfered with the chronograph stop sensor.  I've always tried to get chronograph as close to the test block as possible, but I think I need to include some additional space for future tests.  Based on all previous shots, impact velocity should have been 1400+ feet per second.

The average expansion of the recovered bullet was .513".  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 1.43.  This means the recovered bullet is 43% larger than the unexpanded bullet. 

Weight Retention:
The recovered bullet from this test weighed 124.5 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 99.6%. 

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 18.3125 inches into the gel.

Wrap Up:
Looking back on the bare gel test results HERE and the stress test results above, I'm really starting to see why the 125 grain .357 Magnum running at 1400+ fps has developed such an enviable track record for terminal performance.  It's obvious that the barrier had an impact on bullet expansion, but it did expand.  Weight retention was outstanding with the Gold Dot bonded bullet.  Some may express concern about the 18+ inches of penetration, observed in this test, for fear of over penetration.  I discount those concerns because internal barriers were not accounted for in our test protocol.   
This test has set the performance bar at a very high level.  It will be interesting to see how other calibers and bullets perform in the stress 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.


  1. What a difference a barrier makes! Now I really want to see how the Hornady Critical Defense or FTX .357 rounds perform on this test.

    My prediction, 1400 fps, .55 avg exp and 13 in penetration for the CD and 1250 fps, .58 avg exp and 14.5 in penetration for the FTX.

    Thanks for another good article.

  2. Thanks for a great post. I'm with Tim- I'd love to see how the Hornady Critical Defense stacks up.