Why recoil “contraptions” don’t, or can’t, tell the truth.

Why recoil “contraptions” don’t, or can’t, tell the truth.

 

We get asked a lot, “What percentage reduction does your brake provide?”, but it’s not an easy question to answer in percentages. The reason is that “felt” recoil is a very subjective quantity, and measuring “feel” is like measuring “taste”, because it’s not the same for everyone.

Now. There are numerous methods of “testing” recoil and reduction thereof, but translating those measurements into “felt” recoil reduction is not a very easy task. I’m going to run down the list of a few different methods people use to measure recoil and recoil reduction, explaining the failings of each. This is not to discredit anyone for their effort(except maybe one, whom I’ve attempted to explain to him where he went wrong so that he could re-evaluate his results instead of committing journalistic malpractice) , It’s merely to point out why it doesn’t tell the whole story.

 

  1. Free Recoil method (no sled) measuring distance traveled. Believe it or not, this is probably the most accurate comparison to “felt” recoil, and obviously the most low-tech. It still isn’t perfect because it is only measuring the distance traveled with no resistance. Resistance is an important part of the equation because your shoulder will provide resistance even without being noticeable or uncomfortable, whereas free recoil provides little or none. This goes back to some things learned in the barrel length article, such as recoil velocity is more important than recoil distance only when you reach a certain amount of travel. i.e. A rifle that’s recoiling 10fps at 4” and stops by 6” with brake (a), will have more “felt” recoil than the same rifle that’s recoiling 10fps at 2”, 5fps at 5”, and is still moving 2fps at 8” with brake (b), even though brake (b) traveled farther. (for perspective a 7lb 223 running 55s at 3000fps = 6.2fps recoil speed)
  2. Free Recoil (with sled) measuring distance traveled. This method actually skews the results even farther because you are adding mass, and probably friction, to the equation. Not useful for comparing brakes or assigning percentages, but is a good illustrator of brake vs no brake.
  3. Load sensors with a “mostly” zero, or zero travel setup. I guess the best place to start on this one is by drawing attention to an article that many have read, and a lot taken as gospel, even though his own data shows that he basically measured everything BUT how well the brakes worked (if you have doubts about this run QL or look into how many milliseconds it takes for a bullet to exit the barrel, and compare it to his graph. At .006ms he’s comparing peaks when the bullet isn’t even halfway down the barrel, brakes aren’t doing anything at that point). In fact his video on his test setup shows that what I was telling him was fact( I explained to him that he was measuring the loading of the sensor and frame to the first plateau, and the second plateau showing peak thrust with all preload removed. The rifle then proceeds to launch forward 4”+ as the frame/buttpad/stirrup unload). In the prior article ( https://kahntrol.com/the-effect-of-barrel-length-on-recoil/ ) I explained how a muzzle brake can do exactly NOTHING until the bullet exits the muzzle, and peak recoil occurs while the bullet is accelerating inside the barrel, so using a static load sensor and a no travel set-up, you are only actually going to measure the recoil that a brake can’t stop. (on a side note about the tests performed by the other author, Had he used a bungee, strap, or other method, and actually preloaded the sensor, his readings would have been virtually identical between the different brakes. When you’re dealing with forces that are generated in less than a quarter of an inch, with tremendous acceleration rates, a difference in .010” of preload travel will show huge differences in readings. Also the load sensor in question requires a precision ground(within .0005”TIR) mounting surface and an absolute linear load-path to even think about being accurate. )

 

Before I go any further, I want to state for the record that I have no ill will towards the author mentioned above (I hear he’s a good guy), and I had no dog in the fight for his testing, but I did attempt to explain to him, how and why, his data was flawed before he published the last 6 articles of his testing, but he carried on nonetheless. I honestly felt bad for him after all the time and effort he spent, but passing off flawed data as scientific results should NOT be excused just because you expended time, effort, and money.

 

Is there a scientifically accurate way to measure felt recoil, or the reduction thereof ? Yes. Here’s what would be required:

  1. A chassis type rifle with a collapsible AR style buttstock with the locking pin removed and a load sensor and spacers “properly” installed within the stock between the butt plate and buffer tube, ensuring proper LOP for the shooter.
  2. A break-wire or similar system at the muzzle to log the precise bullet exit moment.
  3. An objective but experienced shooter to pull the trigger, is consistent with shoulder preload, and not run away from the recoil (skewing results).

Using this method would allow you to isolate the recoil forces that occur only after the bullet has exited the barrel, giving you an accurate dataset to compare brakes and also non-braked rifles. In addition you should be able to calculate the resistance and range of travel offered by the shooter in order to devise a mechanical resistance apparatus to simulate the rifle being shouldered without risk of human error to cloud results.

 

So. When people ask “How much reduction can I expect?”, you may not get an answer in percentages, but I can tell you pretty darn accurately what the recoil’s going to be comparable to. And, in 6+ years, no ones accused me of being wrong in my predicting their results.