Push / pull method with an AR?

[JohnKSa]

Some issues:

"Recoil force acts slightly below the bore axis, generating torque that causes the muzzle to rise." This is incorrect. Recoil force acts directly along the bore axis.

"The forward push from the firing hand resists the rifle's backward motion, while the backward pull from the support hand anchors the rifle to your body. Together, they counter the rotational effect." Forward and backward pushes can do nothing to counter "rotational effect". There would need to be some force opposite the force vector that is causing the rotational effect. That force is upwards and so the force would have to be downward, not backward or forward.

It looks to me like it is parroting something it "read" on the internet rather than doing any sort of analysis.

[tangolima]

It is indeed how it works. It searches the Internet and summarizes the result with some analysis. It is like having an intern, who knows little or nothing about the subject matter, to do research for you. It is up to you to accept the results. If the result is off, you question it and it will adjust the analysis.

For instance, you can enter "Explain exactly how the opposing forces can cancel the rotating torque", and it will elaborate. If its logic is wrong, eventually it will be cornered. Then it actually will apologize and start over. It happened when I was grilling it for Rice distribution.

-TL

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[tangolima]

Originally Posted by JohnKSa

Some issues:



"Recoil force acts slightly below the bore axis, generating torque that causes the muzzle to rise." This is incorrect. Recoil force acts directly along the bore axis.

There were exchanges prior to the exert posted. If the context is considered, he is actually correct. The recoil here is the force on shooter's shoulder, which is below bore axis.

He is also correct that the 2 opposing forces create a torque rotating muzzle down.

-TL


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[JohnKSa]

The RESISTANCE to the recoil force is, indeed, the shooter's shoulder which in most designs is somewhat below the bore axis--although much less so in an AR type design.

The recoil force, however, is directly along the bore axis.

He is also correct that the 2 opposing forces create a torque rotating muzzle down.

"He?" Ouch. The algorithm, you mean.

One could argue that the pull force by the rear hand is below the fulcrum of the shoulder which would tend to pull the muzzle downwards. But pushing forward on the forearm (in line with the bore, more or less and either aligned or slightly above the fulcrum of the shoulder) actually counteracts some of that downward torque, it doesn't help it.

Can you draw out the diagram you are thinking of where both the push force and pull force work to pull the muzzle downwards?

[tangolima]

I regard the algorithm as my intern who is male, and hence a he .

I started the chat on felt recoil on the shooter's shoulder, so the "recoil force" is just that. The rifle is conventional stock configuration, such as a pump shotgun, where the wrist is inline with the butt stock, and the bore axis is above the butt stock.

The butt stock contacts the shooter's shoulder. It is the pivot. The pull force on the stock wrist is inline to the pivot, so it has zero torque. The push force is on the forearm and above pivot, so the torque pushes the muzzle down.

AR config is slightly different, but the result is the same. The pull force is on the pistol grip and below the pivot. The torque rotates the muzzle down. The push force is on the forearm and inline with pivot. The torque is zero.

-TL

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[davidsog]

JohnKSa has tried to explain to you that a torque is a moment ABOUT an axis not ALONG an axis.

ChatGP does not understand this concept and your reliance upon it hints to the fact you do not either. That is not a dig at you, just a fact. We all are learning here. Torque effects would be separate conversation and are actually considered minor forces when it comes measuring recoil effects. Most of the time, it is inconsequential and for a conversation of forces felt ALONG the recoil axis it is non-existent.

Once more, the OP question is about forces ALONG the recoil axis:

I mean if the push/pull method lowers the recoil on a shotgun, wouldn't be the same (or even better) on an AR? Can you explain why or why not?

[davidsog]

As the bullet accelerates forward, the gun HAS to accelerate rearward. No free lunch here, guys. Since these forces are equal, the equations can look something like this: F=ma(gun) = F=ma(bullet) Since the forces are equal, taking the difference of these will always give you zero. This explains the reason that if the new hand load you worked up has your bullets going faster or your rifle goes on a diet, this translates into a healthy dose of increased rifle recoil because the rifles acceleration will increase.

Small changes in acceleration have a large effect on the forces you feel in our F =ma.

You say "Big deal, you increased the acceleration of the rifle by 1.34%". You are correct, but look at it from the perspective of increasing the rearward acceleration of the rifle by 43.8%!

https://www.thealaskalife.com/blogs/...ng-the-physics

[Pumpkin]

If an 8lb 308 is fired in a rest, by itself would it recoil and jump more than the same rifle mechanically affixed to a 200lb shooter?

Would this not effectively change the weight of the rifle to a much greater amount thereby reducing Felt recoil?

Now, both examples are no where near being 100% realistic but to a varying degree my shade tree reasoning says they are.
Maybe mathematically the solution would be different but real world, real shoulders might contradict the calculated answer.

[davidsog]

If an 8lb 308 is fired in a rest, by itself would it recoil and jump more than the same rifle mechanically affixed to a 200lb shooter?

Both rifles will have same exact recoil energy.

They may or may not have the same felt recoil depending on specifics of the mechanical affixation and the specifics of the rest.

The math will very much back up real world observation. Now, this is not actually calculating the specific forces, it just illustrates the mathematical relationship found in the real world.

You can see that in the effect of weight on acceleration.

Recoil Force of 150 grain .308 Win = 15.6lbs

a = F/M

Mass = 8lb / 32.2fps = .248 slugs(lb*s^2/ft)

Our 8lb Rifle acceleration is

a = 15.6lb/.248lb*s^2/ft = 62.9fps^2

Our 20lb Rifles Acceleration is

20lb rifle = .621 slugs (lb*s^2/ft)

a = 15.6lbs/.621lb*s^2/ft = 25.12 fps^2

Our 20 lb rifle moves almost a third of the distance in the same amount of time for the same amount of force. We experience that as a reduction in felt recoil even though it is the same amount of force.