Measuring rifle kick

[rogerg12]

So, I've got a Serbu BFG-50. I want to measure a bunch of values (e.g., precision, noise, weight, bullet speed, etc.) with the gun in three scenarios: without a muzzle brake, with a muzzle brake, and with a 16" suppressor. No other reason than I'm just interested to see if my understanding and perceptions will hold up to real world testing.

For sure, I already know that I get a much bigger kick (just painful) when shooting with the suppressor versus the muzzle brake. I want to measure the differences in kickback between the three scenarios.

Anyone know of a device or contraption that would accurately measure the kick?

 

[6.5SH]

There was a tool to measure the force of recoil but it has been discontinued. You can get an idea of what it would take to build your own from their product page and user manual:

RSI - LoadForce Neck Tension Meter

System to Measure Neck Tension and Felt Recoil

www.shootingsoftware.com

While not exactly what you are trying to measure, an accelerometer would give you the ability to compare the 3-Axis G forces between your configurations.

Rifle Accelerometer Update

This DIY rifle accelerometer has been upgraded through open-source contributions, including a 6X speed boost and much more!

blog.ammolytics.com

 

[rogerg12]

There was a tool to measure the force of recoil but it has been discontinued. You can get an idea of what it would take to build your own from their product page and user manual:

RSI - LoadForce Neck Tension Meter

System to Measure Neck Tension and Felt Recoil

www.shootingsoftware.com

While not exactly what you are trying to measure, an accelerometer would give you the ability to compare the 3-Axis G forces between your configurations.

Rifle Accelerometer Update

This DIY rifle accelerometer has been upgraded through open-source contributions, including a 6X speed boost and much more!

blog.ammolytics.com

Thanks for the suggestions.

 

[msgriff]

Muzzle brake testing videos to illustrate one test sled design to measure compare one aspect of recoil. with the muzzle device being the only variable.
Muzzle Brake Tests
Edited for clarification

 

[rogerg12]

Muzzle brake testing videos to illustrate one test sled design to measure recoil.
Muzzle Brake Tests

Yep, that's definitely the type of thing I'm looking for. That's fairly expensive looking if someone sold one and looks like it would take a fairly long time to create one if built by hand. But definitely what I'm looking for.

 

[W54/XM-388]

So, I've got a Serbu BFG-50.

Do yourself a favour and get rid of it and get yourself something properly built and reliable.
Such as an Armalite AR-50A1 or something similar.

If anything goes wrong with your ammo on the Serbu you might be lucky to survive.

 

[FWoo45]

^^^^What he said^^^^
Just gonna leave this here.

50 Bmg Blow up....

Boy was I cringing the whole time watching this video.... He blames it on the "hot" slap round, but that particular 50 cal rifle(if one can even call it that) looks flimsy as hell for a 50 cal. Be careful out there...

www.snipershide.com

 

[smoothy8500]

I want to measure a bunch of values (e.g., precision, noise, weight, bullet speed, etc.)

I guess "my life" falls under etc.

 

[rogerg12]

This was not intended to be a Serbu 50 thread. But the single failure was due to the ammo being loaded with handgun gunpowder instead of rifle powder, so the chamber pressures ended up at over 450,000 lbs, well beyond the design limitations for any 50 cal, regardless of vendor. Serbu has for years been telling people to watch out for bad or suspect ammo. They go so far as to list the refutable ammo vendors to buy ammo from to prevent malicious re-loads.

 

[whatsupdoc]

This was not intended to be a Serbu 50 thread. But the single failure was due to the ammo being loaded with handgun gunpowder instead of rifle powder, so the chamber pressures ended up at over 450,000 lbs, well beyond the design limitations for any 50 cal, regardless of vendor. Serbu has for years been telling people to watch out for bad or suspect ammo. They go so far as to list the refutable ammo vendors to buy ammo from to prevent malicious re-loads.

Could you please post a link detailing where the said ammo was sent and tested?

 

[wadebrown]

Muzzle brake testing videos to illustrate one test sled design to measure recoil.
Muzzle Brake Tests

The physics involved here tells me this is a measure of recoil energy not necessarily force. I am not saying this is a poor way to evaluate muzzle breaks because the shooter is better off if he/she does not absorb the recoil energy that is redirected by the brake.

I think felt recoil is a function of both the force felt and the time this applied. Think about shooting a 338 Win Mag vs say a 375 H&H, the 338 tends to be known as a bruiser and the 375 not so much. What I have felt and others also is the 338 is a sharp crack vs the 375's gentle push, these are both without brakes. I regularly shoot one of my two Ruger 375's without worrying about injuring my thrice rebuilt right shoulder, I shoot right-handed, I would be more careful shooting a 338 Win Mag. I do not own a 338 Win Mag, my only 338 is an Edge and it sports a brake so I do not compare it to the unbraked 375's.

That is where a sensor system like RSI built is probably a better solution as it used to measure Force applied versus time, instead of just maximum force. The faster the force is applied the worse it is going to feel, it has to do with impulse, that is why you have to measure the force over time.

I hope this makes sense, I can't say that I would bet my life or multiple physics degrees on what I have said without more measurements but I am reasonably certain about the measurement of force applied versus time as a better measurement of the recoil "felt" by the shooter. I am open to differences of opinion as that is one way we all reach a better understanding.

 

[msgriff]

The physics involved here tells me this is a measure of recoil energy not necessarily force. I am not saying this is a poor way to evaluate muzzle breaks because the shooter is better off if he/she does not absorb the recoil energy that is redirected by the brake.

I think felt recoil is a function of both the force felt and the time this applied. Think about shooting a 338 Win Mag vs say a 375 H&H, the 338 tends to be known as a bruiser and the 375 not so much. What I have felt and others also is the 338 is a sharp crack vs the 375's gentle push, these are both without brakes. I regularly shoot one of my two Ruger 375's without worrying about injuring my thrice rebuilt right shoulder, I shoot right-handed, I would be more careful shooting a 338 Win Mag. I do not own a 338 Win Mag, my only 338 is an Edge and it sports a brake so I do not compare it to the unbraked 375's.

That is where a sensor system like RSI built is probably a better solution as it used to measure Force applied versus time, instead of just maximum force. The faster the force is applied the worse it is going to feel, it has to do with impulse, that is why you have to measure the force over time.

I hope this makes sense, I can't say that I would bet my life or multiple physics degrees on what I have said without more measurements but I am reasonably certain about the measurement of force applied versus time as a better measurement of the recoil "felt" by the shooter. I am open to differences of opinion as that is one way we all reach a better understanding.

Edited my post (#4) for clarification.

 

[Marine52]

JBM - Calculations - Recoil

www.jbmballistics.com

 

[Zak Smith]

We have an accelerometer that we can hook up the same the data-acquisition unit we normally do sound measurements with. The data is somewhat problematic to analyze, but it does allow us to differentiate peak force from overall impulse.

 

[rydah]

Depends on what data you’re after.

Accelerometer, force gauge and a sled/pendulum can all give you different data that’ll allow you to compare which is more effective at reducing the forces applied to the shooter but depending on which you use will get much different data.

In my experience a sled is probably the cheapest way to do it but once you start considering the forces from a 50 bmg things get very expensive very quickly.

 

[wadebrown]

We have an accelerometer that we can hook up the same the data-acquisition unit we normally do sound measurements with. The data is somewhat problematic to analyze, but it does allow us to differentiate peak force from overall impulse.

Overall impulse and peak force would be great, you might have to take the measurements on different shots but if load is the same they should correlate well.

 

[paulrem308]

Remember saw a formula couple years ago to calculate recoil. Apparently my Google Foo sucks and can't find it. Believe used bullet weight, velocity, gun weight, etc. Anyone know what I'm talking about.

 

[hlee]

Remember saw a formula couple years ago to calculate recoil. Apparently my Google Foo sucks and can't find it. Believe used bullet weight, velocity, gun weight, etc. Anyone know what I'm talking about.

F=MA; where F= force, M=mass, and A=acceleration.
Furthermore, KE= (1/2)MV^2; where V= velocity.
We can calculate the velocity of the rifle from the steady state equation below;

M(rifle)*V(rifle, initial) + M(projectile)*V(Projectile, initial) + M(powder)*V(Powder, initial) = M(rifle)*V(rifle, final) + M(projectile)*V(Projectile, final) + M(powder)*V(Powder, final)
Recognizing that the initial velocities of all components of the system are 0, we can reorganize the equation as below;

V(rifle, final) = -(M(projectile)*V(Projectile, final) + M(powder)*V(Powder, final)) / (M(rifle))
The (-) is a function of the bullet and other "ejecta" moving in one direction while the rifle is moving in the opposite direction.

Note that; given an equivalent bullet weight, bullet velocity, powder charge, and rifle weight, the recoil velocity of the rifle will be the same regardless of the cartridge used. Further, the recoil energy of the rifle will be equivalent- regardless of the cartridge used. But, what we cannot easily calculate- with high school physics- is the acceleration of the rifle to that final velocity. We do know, however, that the acceleration of the rifle will take exactly the same amount of time as it takes for the ejecta to traverse and exit the barrel. After measuring that number, we can divide the final rifle velocity by the total "acceleration time" to empirically derive the rate of acceleration.

The difference between the 338 weatherby mag and the 375 H&H (if there be an actual difference in recoil metrics) is the acceleration of the rifle. The acceleration of the rifle is the missing variable in the Force equation.

Beyond that, "felt recoil" is very much a function of rifle fit/form, and the body composition of the shooter. My 400 lb uncle will have a very different felt recoil experience, as compared to my 160 lb frame- all else being equal.

And, adding a muzzle device that slows/redirects the expanding gasses as they exit the bore render the above equations invalid- or at least not easily applicable.

 

[SJ77]

Can't help you on recoil 'force' but have seen a system recently that looked at the muzzle 'rise' (vertical and / or horizontal movement of the muzzle or deviation from plane).. it was a highspeed camera looking at a graduated target board and a laser was used to measure the deviation from plane. Provided some good data on the effectiveness of a sample of prototype brakes against each other.

 

[acudaowner]

or you could build one of these


though the calculator posted above might be a lot easier .

 

[fdkay]

 

[Oldloser]

There are accelerometer apps for your phone. Take it from there.

 

[308pirate]

There are accelerometer apps for your phone. Take it from there.

Put the phone between your shoulder and the rifle's buttplate.

 

[ToddM]

If you really want to get fancy they make some various 3 axis accelerometers they use in crash testing that record 500,000+ measurements a second, we used to use them for pressure wave characterization for more fun things. You could also use something like the MantisX. It's mostly marketed for handgun training, but it has a feature than when clamped to a gun, it uses a 3D accelerometer to basically track muzzle position before, during, and after the shot. I've always thought it would be interesting to use the MantisX for rifle training as you could experiment with your position and really get a hopefully repeatable measurement of how well you are managing recoil. In theory you could also get realtime feedback on how positional changes improve stability if you were experimenting with your position, rifle balance etc. I know pro level archers that use them to adjust bow poundage, bow balance etc. because they get an instant, measurable, and consistent feedback on if they have increased their stability, during the aiming process, and during the shot/follow through. What used to take them months to fine tune they can now do in weeks.

That said I feel there's a lot more to recoil than just force, the recoil impulse matters a lot. Case in point, I'll shoot a 71oz .500 S&W magnum all day long, but twelve max .44 mag rounds through 25oz S&W 329PD and that's enough. It's not the raw "push", it's how sharp the recoil is. I'd imagine the same is true for recoil management in a rifle. A slower recoil impulse is probably easier to manage than a sharp fast one. I'd imagine the same is true for muzzle brakes, in theory being able to put a accelerometer on the gun that tracks how it moves under recoil would not just measure recoil reduction, but how the muzzle brake impacts the tracking under recoil during the shot. It could help tune some of the adjustable variable port muzzle devices. In theory I suppose you could combine that with a high speed camera, so you could only look at the data until the bullet left the barrel, since it doesn't matter what the gun does after that.

 

[rogerg12]

The physics involved here tells me this is a measure of recoil energy not necessarily force. I am not saying this is a poor way to evaluate muzzle breaks because the shooter is better off if he/she does not absorb the recoil energy that is redirected by the brake.

I think felt recoil is a function of both the force felt and the time this applied. Think about shooting a 338 Win Mag vs say a 375 H&H, the 338 tends to be known as a bruiser and the 375 not so much. What I have felt and others also is the 338 is a sharp crack vs the 375's gentle push, these are both without brakes. I regularly shoot one of my two Ruger 375's without worrying about injuring my thrice rebuilt right shoulder, I shoot right-handed, I would be more careful shooting a 338 Win Mag. I do not own a 338 Win Mag, my only 338 is an Edge and it sports a brake so I do not compare it to the unbraked 375's.

That is where a sensor system like RSI built is probably a better solution as it used to measure Force applied versus time, instead of just maximum force. The faster the force is applied the worse it is going to feel, it has to do with impulse, that is why you have to measure the force over time.

I hope this makes sense, I can't say that I would bet my life or multiple physics degrees on what I have said without more measurements but I am reasonably certain about the measurement of force applied versus time as a better measurement of the recoil "felt" by the shooter. I am open to differences of opinion as that is one way we all reach a better understanding.

Thanks Wade and everyone for your suggestions and comments.