Why do some powders have more recoil?

[stubert]

Same bullet, same velocity, same caliber, why does changing powders change how recoil feels? This is hypothetical, I have had alot of people tell me this.

[JeffinNZ]

The weight of the powder charge is part of the recoil factor as much as the projectile is. If one charge has 20gr and another has 40gr the heavier charge for the same bullet weight will produce more recoil. I suspect the speed of the burn also contributes but I will need some input on that from more knowledgable folk.

[rosewood]

There are a lot of factors that affect real measurable recoil and perceived recoil. A larger powder charge with the same speed will have more real recoil than a lighter powder. The equation for recoil is calculated using the gun weight, boolit weight, powder weight and boolit velocity. However, slower burning powders that recoil more also have a longer recoil impulse as they are pushing on the boolit longer to attain the higher velocity so the gun is pushing back on you with the same total force over a longer time period, so may be more of a shove instead of a jab. Faster powders have less recoil, but have a shorter recoil impulse and may feel more snappy or quicker jab on your shoulder. That being said, it is really hard to determine how it will be felt until you actually shoot one. Basically, it all looks good paper but the real world application requires you to shoot one.

As for perceived recoil, a louder explosion makes you think it recoiled more. You are getting sensor overload with a quick jab on the shoulder and loud report occurs at the same time. A more recoiling load may seem less recoil if it isn't as loud. I have a prime example, using H322 in my 10" 7tcu sounds like a cannon going off and seems to be recoiling a lot. Using 2400 with the same boolit and less powder is much quieter, but it actually has more calculated recoil because the boolit is a good bit faster, however my perceived recoil in the H322 is more.

Confused yet?

Rosewood

[Wayne Smith]

I'm betting most of it is in the amount of explosive gasses ejected from the muzzle at the time of firing. Speed of burning affects this greatly, the faster burning the less ejected hot enough to burn when it hits O2.

[rosewood]

Yes. Those gasses is the mass of the burnt powder that is used in the equation. However gun powder has its on oxygen in the mix and doesnt need oxy from the air. It just doesnt burn before it leaves the bbl when it is a slow burn powder. That causes more report and more muzzle flash.

[jaysouth]

When I used to shoot skeet and trap, it was accepted as gospil that Red Dot had more recoil than Green dot and that 700X had the worst recoil of all. I never figured out how to validate or debunk this, but there are shooters who still repeat this. It all seemed very subjective to me.

[runfiverun]

think about accelerating in your muscle car.
half throttle = eh but you'll get to 60.
hammer down on that pedal and it pushes you back into the seat like crazy and you get to 60 much sooner.

pushing a 230gr boolit to 850 fps produces recoil quite similar in force [rearward motion] no matter how you get there.
you feel the slam differently than you feel the gentle acceleration.
bullseye= slam.
unique= acceleration.
both= equal 60 mph.

[smokeywolf]

Naturally, in addition to the expanding gases propelling the boolit forward, they are of course propelling the firearm rearward. Part of the equation also is the amount gas still expanding from powder that is still burning when the boolit clears the muzzle of the firearm. Once the boolit has left the barrel the gases exhaust out the muzzle unrestricted and act like the exhaust nozzle on a jet airplane. This phenomenon would also explain why a larger amount of powder with a more sustained burn might produce a greater amount of gas resulting in a continued jet propulsion effect at the muzzle after the boolit has departed the firearm and is making its way to the target.

smokeywolf

[TXGunNut]

I think it has something to do with pressure. Load "A" may require a higher pressure to reach the same velocity as load "B". Going back to the shotgun anecdote some skeet shooters prefer lower pressure loads to lessen perceived recoil. That somewhat jibes with what rosewood was saying but sometimes it's just a matter of perception. Some shotgun (and rifle and handgun) designs handle recoil differently from others and of course technique can make a difference as well. I'm not recoil sensitive (to a point) so it's not a big deal to me anyway.

[Slow Elk 45/70]

I have always just been a simple man, yes there are a lot of factors as has been pointed out. boolit weight, powder burn rate.....same boolit, faster powder, more felt recoil as it burns fast. Slow burning powder to same velocity feels less recoil as the powder burns slower, so you feel more like a push than a slap....not rocket science for simple folks like me...Kiss method... good luck and good loading

[sdcitizen]

In most centerfire rifles with factory loaded ammunition, a large chunk of recoil is the jet effect as has been explained. Relatively slower burning powders have a higher residual pressure when the bullet exits the muzzle. Think about the difference between 8000 psi and 12000 psi, this is the range on say a 30-06. In a lighweight rifle this difference in pressure could be between 60% and 80% of felt recoil.
On a side note, if the powder has reached proper pressure to burn properly, it is all consumed within inches of the chamber, no matter how 'slow' the powder is. The muzzle flash is caused by hot carbon monoxide igniting when it hits open air.

[303Guy]

I became aware of the jet effect with my suppressors in the form of muzzle lift which is quite slow and gentle but can't be stopped even though the rifle recoil itself is slight as in hardly noticeable. I reason that the slower powders have a better brake effect but more jet effect exiting the can. Even the humble 22 hornet has more muzzle lift with a can than without (and of course, more recoil without a can - if one can call it recoil!) when using a compressed load of Lil'Gun. So one can imagine the jet effect at the muzzle.

I've noticed that when using two different bullet weights in the Brit with the same powder and loaded to the same pressure that the heavier bullet load has more of a push than a kick compared to the lighter bullet load which has a sharper kick, even though the recoil momentum of the heavier bullet load is greater.

[Elkins45]

Slower powders spread the recoil impulse out into a push over a longer time. With fast burners you get all of it in one short jolt.

[rosewood]

Chamber pressure has nothing to do with recoil. Recoil is calculated by boolit weight, powder weight, velocity, and weight of the firearm. A .223 can have 4 times the pressure of a 45-70 yet recoil is significantly less. Although chamber press is a function of boolit weight, burn rate and velocity. This jet effect is caused by mass leaving the barrel in the form of a gas Instead of a solid, I.e. the boolit. Still the total mass leaving Is ehat determines the recoil. Force=mass x acceleration. The eq for recoil does dumb It down a bit and makes some assumptions. As In any thermo dynamic reaction, there are so many different variables It Is Impossible to be calculated exactlly. But u can measure It. I guess the suppressor is spreading the recoil across a longer period of time giving a more continuous push instead of a jolt.

[BAGTIC]

It is not pressure alone. It is force times area. The .223 may have twice the pressure but the 46-70 has 5.5 X the area. Also involved is the inertia of the projectile/powder vs the mass of the gun. Mass going forward vs mass going backward. The weight of guns is seldom proportional to ejecta weight or bore area. The typical 55-60 grain and 25-27 grains of powder in a .223 is not proportional to the 405-500 grain bullet plus powder of a 45-70.

[rosewood]

That was an extreme example. My point was more pressure doesnt mean more recoil. Pressure isnt in the equation.

Velocity is a function of the pressure on the boolit over time. Slow powder may be lower press but it pushes longer. Faster powder may be higher pressure but for a shorter period of time. Pressure is not indicative of recoil.

[uncle joe]

runfiverun and Elikns45 have it. Think of it like the old physics teacher would tell you to. Getting the bullet to a certain speed requires work. Work is a factor of time and thus the faster you do the same about of work the more energy is needed but it gets done faster. The only things that have much to do with recoil are the weight of the gun and bullet which is what's going to go through the distance, and the force required to make it happen in a certain amount of time.

[Larry Gibson]

Slower powders spread the recoil impulse out into a push over a longer time. With fast burners you get all of it in one short jolt.

Given the same muzzle velocity this is correct. The typical formula for computing recoil only computes the end product. That formula does not compute the velocity of the rifle to the rear which, in essence, is where felt recoil comes from.

Larry Gibson

[NavyVet1959]

Recoil is the momentum and according to the Conservation of Momentum law, the momentum of the bullet + gases + ejecta is going to equal the momentum of the gun when fired. That's all fine and dandy from a theoretical standpoint, but from a practical standpoint, felt recoil is going to have to also take into account the length of time over which that momentum is applied.

Considering how a particular powder can have different burn characteristics depending upon how it fills the cartridge, I don't see a way to create a single number that could be assigned to a powder that would allow for any sort of mathematical method for calculating the felt recoil. Mechanically measuring it would not be all that difficult though. You would just need a fixed barrel with a strain / force sensor behind the breech of the "firearm" that could log the force applied to it in in real-time with a sufficient number of measurements logged for the entire time that the bullet was in the barrel plus a bit extra to take into account the time that the gases + ejecta are also affecting the perceived recoil. If you were to graph this, I suspect that the area under the curve would relate to the calculated recoil (momentum) whereas the height of the line and duration would relate to whether it was a "kick" or a "push".

[rosewood]

Well said NavyVet! And thanks for your service.