Quick observation: speeding kills more people per year than rifles do.
Because this is the internet, sourcing is important:
https://ucr.fbi.gov/crime-in-the-u....016/tables/expanded-homicide-data-table-4.xls - in 2016, 374 people were killed with rifles. (As an aside, more people were murder by knives/cutting, blunt objects, and fists/feet/hands than rifles.)
https://www.nhtsa.gov/risky-driving/speeding - in 2017, 9,717 people were killed because of speeding. That's about 30x a bigger problem than rifles.
You shouldn't be so unwilling to be suspicious about statistics. Virtually everyone is speeding pretty much all the time (review the 85th percentile for almost any stretch of road relative to its limit), thus speed is almost always cited as a contributing factor. Might as well cite breathing as a contributing factor to accidents.
What are the standards for speed to be considered a contriubing factor? 5 over, 10 over?