From Spuhr AB's facebook:
We often espouse the benefits of attaching accessories to our scope mounts rather than to the handguard/forend of a firearm.
Attaching an accessory - especially if it's a laser range finder (LRF) or an IR/PEQ - to our scope mounts will align the accessory with the optics rather than with the handguard, and will also get it up and out of the grass (if shooting prone). Another benefit of using the scope mount as the platform for accessories is that the firearm's center of balance is moved closer to the user.
A recently published study by Jemma L. Coleman, Frank Morelli, Jodie McClelland & Kane J. Middleton, titled, "Can target effects or discomfort ratings discriminate between small-arms weapon configurations?" show that front mounted accessories will increase fatigue, which in turn will decrease accuracy while increasing the time it takes to engage targets.
The abstract reads: "Defence acquisitions use accuracy measures as a discriminating factor in weapon purchases, but assessments are generally completed in static, supported postures at static targets with few differences being seen between configurations. The aim of this study was to investigate whether an assessment requiring repositioning between shots could reveal differences. Participants shot at a static target under four conditions: an unweighted rifle and the addition of a mass fixed at three different positions. Accuracy and timing as well as discomfort measures were captured and compared. Hit percentage, consistency and timing varied over time, and timing increased with the addition of mass in two out of the three conditions. There was an increase in discomfort with the addition of mass further from the participant. The results showed that relying on accuracy and consistency measures alone to make acquisition decisions could have the consequence of purchasing equipment not fit for the human."
The practitioner summary follows with, "This research shows that relying on accuracy and consistency measures alone to make weapon-system acquisition decisions could have the consequence of purchasing equipment not fit for the user. Further research should focus on ‘upstream’ issues such as muscle fatigue and aim point stability in order to better understand human-weapon-system interactions."
The study can be downloaded here:
https://www.tandfonline.com/doi/abs/10.1080/00140139.2020.1834625