M&P Monday: Week Ten

29-Jun-08 – 00:30 by ToddG

20,971 rounds
2 stoppages, 0 malfunctions, 0 parts breakages

It was a very busy week in the M&P Torture Test. Before shooting began, an armorer performed the 20,000 round service interval. We also installed the new Performance Center sear, replacing the gunsmithed one. The result was a 6½ pound trigger pull which dropped down to 6¼ pounds after about 1,500 rounds.

So how is it shooting with the heavier trigger? Pretty well! Here on the left is a picture of the Dot Torture drill shot 50-for-50 at 8 yards, a new personal best for me. The high visibility tape on the front sight (mentioned last week) definitely made a difference in getting those hits.

The trigger, while heavier, has a smooth takeup and break. The Massachusetts-compliant trigger bar and trigger return spring increase the weight from the 4.5# nominal for the Performance Center sear, and also provide a much stronger, more positive reset for fast followup shots.

Sixty-four days after beginning the test we hit the twenty thousand round mark. This took 30 trips to the range adding up to a total of almost 110 hours!

This week we also experienced a true ammunition-induced malfunction. During routine practice, I experienced a stoppage which was not solved with a simple tap-rack-bang.

A look at the gun showed that the primer had blown out of the 115gr Blazer FMJ ammunition. As you can see in the picture to the right (taken by my SIGophile friend Four with his cell phone), the primer was blown completely out of the cartridge case. The case got stuck in the chamber which is what caused the malfunction. It took a knife for me to pry the case out.

Because the malfunction was absolutely and unquestionably caused by the ammunition, it will not be counted against the gun in the test.

This week I also put about 750 rounds through the gun using an Arredondo extended base bad with an ISMI extra-power magazine spring. The result is a 22-round magazine that worked with 100% reliability. There are two spring plates that come with the base pad. We definitely recommend the L-shaped locking plate … it will ensure that the base pad stays in place even when the magazine is dropped on the ground when loaded. {photo linked from the Arredondo website)

Finally, upon reaching the 20,000 round mark, we performed another accuracy test. The gun was not cleaned before the test this time, yet it turned in excellent scores. Obviously, the gun and barrel are still working as well as they were when brand new. Numbers are based on an average of five 5-shot groups fired at 25 yards.

  • Federal 124gr +p HST: 1.69″
    • week 1: 1.46″
    • week 6: 2.05″

If not for a flyer in one group, the average would have been 1.49″! Here’s one of the groups, measuring 1.13 inches:

See you next week …

Train hard & stay safe! ToddG

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  1. 5 Responses to “M&P Monday: Week Ten”

  2. i’m sure this is a dumb question but how does a primer blow out of a bullet?

    By David on Jun 30, 2008

  3. David,

    A primer blows out of a case (not the bullet) usually because the pressure level of the round is excessive for the “system” of ammo and weapon in combination. Primers are usually the first component of an overpressure round to fail and they may flatten and flow, pierce or blow, depending on the circumstances. Take the overpressure further and you see case head failures; further than that and you see barrels/chambers coming apart in catastrophic failures.

    By Wayne Dobbs on Jun 30, 2008

  4. Thanks WD!

    By ToddG on Jun 30, 2008

  5. thank you for the reply! i had something entirely different pictured so i actually learned something!

    By David on Jun 30, 2008

  6. I had a similar malfunction with factory ammo a while ago in a CZ pistol. When I checked the rest of the rounds from the batch I had brought with me there was almost no crimp, or neck tension. As the round fed the bullet was pushed back in the case driving the pressure up. I ended up taking the whole lot home and running them through a Factory Crimp die. I had to chuckle at the irony of running factory ammo through a factory crimp die. You can’t check every round though, so having some type of tool handy is always a good plan – that type of stoppage can be a pain to clear.

    By Ian on Jul 1, 2008

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