S&W M&P Shield 2.0 45ACP upgrades! MCARBO spring kit, polishing, drifting sight… is it fixed?

Published on April 29, 2026
Duration: 5:07

This guide details the process of upgrading the Smith & Wesson M&P Shield 2.0 in 45 ACP by installing an MCARBO spring kit and performing polishing on key internal components. The objective is to significantly reduce trigger pull weight and improve overall firearm accuracy. The process also includes adjusting the rear sight to correct leftward shooting tendencies.

Quick Summary

The S&W M&P Shield 2.0 45 ACP's trigger pull was significantly improved using an MCARBO spring kit and polishing internal components, reducing the average pull weight from over 8 lbs to approximately 3.5 lbs. The rear sight was also adjusted to correct leftward shooting.

Chapters

  1. 00:00Introduction & Accuracy Issues
  2. 00:34Observed Shooting Performance
  3. 00:58Decision to Upgrade
  4. 01:14Initial Trigger Pull Measurement
  5. 02:06MCARBO Spring Kit Components
  6. 02:39Polishing Kit Details
  7. 03:18Post-Modification Trigger Pull Measurement
  8. 04:03Trigger Pull Weight Reduction
  9. 04:23Carry Considerations & Sight Adjustment
  10. 04:57Expected Accuracy Improvement

Frequently Asked Questions

What were the main accuracy issues with the S&W M&P Shield 2.0 45 ACP before modifications?

Before modifications, the firearm consistently shot low and slightly left at both 12 and 25 yards. This was attributed to a stiff, gritty trigger pull and potentially misaligned sights.

How much did the MCARBO spring kit reduce the trigger pull weight on the Shield 2.0 45 ACP?

The MCARBO spring kit, combined with polishing, reduced the average trigger pull weight from 8 pounds 13.2 ounces down to 3 pounds 6.6 ounces, a reduction of over 5 pounds.

What components are included in the MCARBO spring kit for the S&W M&P Shield 2.0?

The MCARBO spring kit typically includes springs for the striker block, striker, trigger return, and sear, along with a centering pin and sandpaper for DIY polishing and tuning.

How was the rear sight adjusted to improve accuracy?

The rear sight was drifted from the left side of the frame over to the right side. This adjustment is intended to correct for a tendency of the firearm to shoot left.

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