"Fast" AR

[rob_s]

How would one go about measuring recoil and the recoil-reduction in a scientific, data-driven way? I have a Battlecomp and a mid length gas system on my rifle, and shooting it back to back with my dad's rifle with an A2 birdcage and carbine gas, it seems to me that my gun has less felt recoil than his. What's the next step if one wanted to take the "felt" part out of that, and is it feasible for most shooters? Pressure sensor on the butt of the rifle? High speed video and a vertical scale to measure muzzle rise?

The way I see it there are two aspects to this. The first is a purely physical, which is sort of irrelevant but still good information to have) on it's own. Pressure sensors, accelerometers, and other measuring devices, etc.

The second would be to measure your own performance. Shoot several drills that have to do purely with the mechanics of driving the gun, or quickly shooting multiple rounds onto a single target, and measure your time and group size. The relies a little more on an experienced shooter as shooters on the lower end of the spectrum and extreme high end will get the most out of widgets. Low end because they are inexperienced and the gizmos will mask their flaws, high end because they can truly take advantage of the benefits.

By doing either you would put yourself into the one percent of gun owners that even bothers to try.

[Magic_Salad0892]

The last part is not directed at you.

You're right. I shouldn't have posted based on theory, and I apologize if you think I threw stupid bullshit into your thread for no reason. That wasn't my intention.

But I still think that a lightweight, short gun is the answer. From my experience running short barrelled guns.

[Arctic1]

The way I see it there are two aspects to this. The first is a purely physical, which is sort of irrelevant but still good information to have) on it's own. Pressure sensors, accelerometers, and other measuring devices, etc.

The second would be to measure your own performance. Shoot several drills that have to do purely with the mechanics of driving the gun, or quickly shooting multiple rounds onto a single target, and measure your time and group size. The relies a little more on an experienced shooter as shooters on the lower end of the spectrum and extreme high end will get the most out of widgets. Low end because they are inexperienced and the gizmos will mask their flaws, high end because they can truly take advantage of the benefits.

By doing either you would put yourself into the one percent of gun owners that even bothers to try.

I don't really think that it is possible to get good objective data on this.

Primary recoil (momentum of gun-bullet system) and free recoil (recoil energy of firearm not supported from behind) is relatively simple to calculate. Secondary recoil is much more complicated. Felt recoil is futile to calculate, as the human factor plays too big a role. Body mass, body type, grip, stance, experience, firearm adjustment, external stressors etc all play a role in how free recoil is dealt with and how a shooter is able to compensate for or overcome the effects of secondary recoil.

No doubt that experienced shooters like yourself, F2S, Surf etc could see drops in split times, transition times etc. But it would still be subjective data defined by your experience etc. As in one shooter can say that a muzzle break, for example, gives an average of .05 seconds faster split times, but you cannot get data saying that a certain device or setup will shave off .05 seconds on split times for everyone.

[MistWolf]

It would be possible to collect objective data, both for the rifle alone and the rifle/shooter. Just mount accelerameters to shooter and rifle and chart the recoil and the recovery. This will produce data of the attack, peak and fade of the recoil and recovery and will graph how each modification of equipment and stance affects recoil and recovery. The data can be compared to split times etc. to determine what recoil and recovery profiles allow the best speed and what modifications to stance and equipment produces that profile

[Arctic1]

For one weapon and one shooter, yes.

If one weapon configuration reduces the effects of recoil by say 30%, compared to a stock weapon, it is not given that every shooter can take full advantage of that in terms of splits between shots, splits between targets and group size.

Body mass, body type, experience/training level, external stressors, stance, grip etc will have too much influence on results during live fire.

Maybe we can say that it is possible to measure recoil reduction potential?

[MistWolf]

There is a difference between free recoil and felt recoil. Free recoil can only be reduced by increasing weapon mass, reducing ejecta mass, reducing ejecta velocity, or a combination thereof. It's attack, peak and fade changed by other means to change how it affects the rifle/shooter combination but the amount of free recoil remains the same. What we are talking about in tuning felt recoil isn't recoil reduction, it's recoil control. (Muzzle brakes simply redirect recoil energy and so affect felt recoil but do not reduce free recoil.)

While the data collected for one rifle/shooter may not be the same for others, trends will appear. Trends have already appeared in stance and usable equipment. For example, as a kid, I found myself reaching out on the forearms of my rifles when tracking running jackrabbits & bunnies. I noticed other folks, in particular my father who was real good at rolling running jacks, did the same. To us, it was just another tool in our bag of shooting tricks. But an informal analysis shows this is a trend which gives us a good starting point for most shooters.

I do agree with Rob that without a formal analysis of data collected in a scientific manner, we do not know what we do not know. What we think is working may in actuality, be masking a problem we haven't discovered yet

[Arctic1]

My understanding of recoil is this:

Primary recoil is the momentum of the gun-bullet/gas system. It is not the main recoil felt when shooting, but still noticeable.

This can only be changed by changing the mass and velocity of the projectile/gas, or the mass of the weapon. Newtons 3rd Law.

Dividing the forward momentum of the bullet/gas with the mass of the weapon, and you will get the rearward recoil velocity of the weapon.

When the weapon is being held by a shooter, the actual weight of the weapon changes drastically, so the amount of primary recoil will be much lower.

Secondary recoil is the main recoil felt, and is a result of hot, expanding gases shooting out of the muzzle, causing the muzzle to recoil like a rocket. This is what causes muzzle flip/rise.

This recoil can, on a free floating weapon, be mitigated by muzzle devices that counter muzzle rise, by diverting gases to the sides and up. Don't know how to calculate this, as it is quite difficult.

Free recoil states the recoil energy of the weapon if unsupported from behind. Using this calculator, you can work out some interesting free recoil numbers, by inputting bullet weight, bullet velocity, powder charge and weapon weight:

http://handloads.com/calc/recoil.asp

It also works out the correct weapon velocity during primary recoil, as it includes the mass of the expanding gases.

On how recoil is perceived, a few things will affect this.
If shooting a weapon with two bullets of different mass, but equal recoil force, then the recoil will be softer when shooting the heavier bullet, as acceleration will be slower due the increased mass because the product of the mass times acceleration must be constant.

Also, reciprocating mass will affect how recoil is perceived, although these do not affect the overall momentum of the system. Buffers and springs will for example affect how slow the recoil energy is delivered.

I agree that by doing a comparison test like you suggested, that you could identify trends that do decrease split times and transition split times, but the human factor will still be a very important factor in how effective these modifications will be.

Surf posted a couple of videos earlier in the thread, doing some trigger comparison drills in one of them. I do not think that I would manage the same splits as him if given the same gun, as he just has a different body mass, different body type, probably physically stronger and more training/experience than me. Maybe one or two hundreths of a second faster. In time though, with training, I could reach the max potential that the system is capable of providing. My splits are usually in the .17-.20 frame while maintaining acceptable accuracy at 5 meters.

[Bluedreaux]

There's also a lot to be said for shooting different combinations and using the one that made you say, "Hot dang, that there don't kick as much."

I'm sure there are better ways, but just going out and using what works is never a bad way to roll.