Does Weight Sorting SK Standard Plus Improve Consistency? A Data-Driven Test

Introduction

Weight sorting .22LR ammunition is a common practice among precision rimfire shooters aiming to improve shot-to-shot consistency. The theory suggests that by grouping rounds of similar weight, variations in velocity and vertical dispersion can be minimized. But does weight sorting actually yield meaningful improvements?

To answer this question, I conducted a test with 100 rounds of SK Standard Plus ammunition, weight-sorted in 0.1-grain increments. Using my CZ 457 LRP and a Garmin Xero C1 Pro chronograph, I measured velocity data, standard deviation (SD), extreme spread (ES), and group vertical spread at 50 meters.

The Weight Distribution

After sorting 100 rounds by weight, the following distribution was observed:

• 51.1gr: 3 rounds

• 51.2gr: 5 rounds

• 51.3gr: 0 rounds

• 51.4gr: 13 rounds

• 51.5gr: 39 rounds

• 51.6gr: 20 rounds

• 51.7gr: 13 rounds

• 51.8gr: 7 rounds

The spread ranged from 51.1gr to 51.8gr, a difference of 0.7 grains across the batch.

Velocity Consistency by Weight Group

The following table summarizes velocity performance by weight category:

Weight (gr)	Avg Speed (fps)	SD (fps)	ES (fps)
Unsorted	1081.6	5.1	13.9
51.1	1083.7	10.1	23.5
51.2	1086.1	3.6	10.4
51.4	1082.9	5.2	13.7
51.5	1085.7	4.6	13.2
51.6	1083.9	4.3	9.8
51.7	1086.2	6.7	19.7
51.8	1089.8	5.6	12.9

Observations:

• The unsorted rounds had an SD of 5.1fps, which is decent but not the best in the batch.

• The lowest SD (3.6fps) was observed in the 51.2gr group, accompanied by a low ES (10.4fps).

• The 51.6gr group also showed good consistency, with an SD of 4.3fps and the lowest ES of 9.8fps.

• The 51.1gr group, with the fewest rounds, displayed the worst performance: SD of 10.1fps and ES of 23.5fps.

• Overall, the heaviest rounds (51.8gr) had the highest velocity (1089.8fps), while the lightest (51.1gr) were among the slowest.

  
  

Vertical Dispersion and Accuracy

At 50m, the vertical spread of each weight group was measured:

Weight (gr)	Vertical Spread (mm)
Unsorted	11.1
51.1	20
51.2	12
51.4	13.3
51.5	14
51.6	9
51.7	7.4
51.8	13

Observations:

• The best vertical spread (7.4mm) was recorded by the 51.7gr group, despite its slightly higher SD.

• The worst vertical spread (20mm) was noted in the 51.1gr group, which also had the highest SD.

• The unsorted group had a vertical spread of 11.1mm, which some sorted groups managed to outperform.

• The 51.6gr group, with one of the lowest SD values (4.3fps), achieved a very tight 9mm vertical spread.

  
  

Environmental Considerations

It’s important to note that the test conditions included a 6mph crosswind, a temperature of 22°C, and a pressure of 29.52 inHg. While these factors were fairly consistent during testing, environmental conditions can play a significant role in the performance of .22LR ammunition. Wind, temperature, and atmospheric pressure affect bullet trajectory and velocity, meaning that even with careful weight sorting, external conditions might mask or amplify the perceived benefits.

Conclusions: Does Weight Sorting Matter?

From this data, weight sorting does appear to have an impact on velocity consistency and vertical dispersion, but the benefits are nuanced:

1. Lower SD generally correlates with better vertical spread, though the relationship isn’t perfectly linear. For instance, the 51.7gr group had a slightly higher SD than expected yet still produced the best vertical spread.

2. The lightest rounds (51.1gr) performed the worst in both velocity consistency and accuracy, suggesting rounds on the extreme low end should be discarded.

3. The heaviest rounds (51.8gr) had the highest velocity but did not necessarily provide the best accuracy, indicating that simply selecting the fastest rounds isn’t the optimal strategy.

4. Certain middle-weight groups (like 51.6gr and 51.7gr) demonstrated significantly better accuracy, implying that targeting a middle range might yield the best overall performance.

However, I do not believe that weight sorting makes a real-world difference for NRL or PRS shooters. The benefit is too small to conclusively attribute it to weight sorting, particularly given the small sample size and the inherent variability of environmental factors.

Practical Takeaways:

• Weight sorting can improve consistency by eliminating outliers, but the overall gains are subtle.

• Optimal weight range selection within a given lot may yield better results than strictly sorting by weight.

• Environmental factors are influential: Even well-sorted ammo can be affected by wind, temperature, and pressure variations.

• For most NRL or PRS shooters, the gains from weight sorting may be too marginal to make a significant impact in competitive settings.

• Future testing will continue to explore whether weight sorting is the key to improved accuracy or if other factors play a larger role.

While weight sorting isn’t a magic solution, it provides an interesting data point in the quest for consistency. For competitive shooters where every detail counts, it might be worth exploring further—but always with the understanding that the practical benefits are small compared to the many variables at play.