Effects of fast vs. slow burning powder on recoil

[dgang]

Just a question: If you were to load a cartridge with a fast burning powder like Red Dot or N310 to achieve a bullet exiting the muzzle at 1000 FPS you might have a high pressure cartridge. Now, load the same bullet with a slow burning powder, IMR4427 or H Lill' Gun, at 1000 fps you might have a low pressure cartridge. Would the recoil, or felt recoil, be the same? Just wondering. Thanks in advance.

 

[fxvr5]

Gunpowders that use a greater charge weight for the same speed produce more recoil. This is consistent with the principle of conservation of mass. Gunpowder weight is part of the formula for calculating recoil force. Slow powders use more weight and therefore produce more recoil force.

Recoil - Wikipedia

en.wikipedia.org

It has a real effect and can be measured.

https://www.shootingtimes.com/editorial/measure-relative-handgun-recoil/99442

 

[dgang]

Then if it weren't for the weight of the ejecta, the recoil would be the same regardless of chamber or barrel pressure spike?

 

[mcb]

Then if it weren't for the weight of the ejecta, the recoil would be the same regardless of chamber or barrel pressure spike?

There would be differences but they are so fast that the human body cannot distinguish them. A accelerometer or pressure sensor at 100,000 sample/sec could measure the differences but the human body just sort of perceives the totality of the recoil impulse.

 

[dgang]

Ok. Thanks.

 

[PO2Hammer]

I don’t think it’s as simple as that.
Slower powders often feel softer, despite the calculations.

 

[mcb]

I don’t think it’s as simple as that.
Slower powders often feel softer, despite the calculations.

Not in my experience. One very distinct example from my reloading. I was working up a new load for my 44 magnum pushing a 240gr JHP. One load used 23.5 gr of H110 (a relatively slow pistol powder) and the other load uses 13.5 gr of IMR 800x (a much faster pistol/shotgun powder). Both loads produced basically the same velocity from my 6.5 inch M29, ~1350fps. The 800x was all around a much more pleasant to shoot cartridge despite being much faster and nearly identical resulting muzzle velocities. The recoil was noticeably lighter (the powder change was nearly 1/2 as heavy), there was no muzzle flash and greatly reduced muzzle blast compared to the H110. Combining those three factors made the 800x a much MUCH more pleasant load to shoot despite both loads having the same resultant velocity.

A much less dramatic change was when I switch from 5.4 gr and N340 to the slightly faster 4.5 gr of N320 in my USPSA Major 40 load. You couldn't feel the difference shot to shot but over the duration of a full USPSA match you did notice a reduction in fatigue using the slightly faster N320.

 

[AJC1]

Not in my experience. One very distinct example from my reloading. I was working up a new load for my 44 magnum pushing a 240gr JHP. One load used 23.5 gr of H110 (a relatively slow pistol powder) and the other load uses 13.5 gr of IMR 800x (a much faster pistol/shotgun powder). Both loads produced basically the same velocity from my 6.5 inch M29, ~1350fps. The 800x was all around a much more pleasant to shoot cartridge despite being much faster and nearly identical resulting muzzle velocities. The recoil was noticeably lighter (the powder change was nearly 1/2 as heavy), there was no muzzle flash and greatly reduced muzzle blast compared to the H110. Combining those three factors made the 800x a much MUCH more pleasant load to shoot despite both loads having the same resultant velocity.

A much less dramatic change was when I switch from 5.4 gr and N340 to the slightly faster 4.5 gr of N320 in my USPSA Major 40 load. You couldn't feel the difference shot to shot but over the duration of a full USPSA match you did notice a reduction in fatigue using the slightly faster N320.

I think other factors like muzzle blast are at play here.... same thing happens with my group size or if the guy next to me is shooting an sbr....

 

[mcb]

I think other factors like muzzle blast are at play here.... same thing happens with my group size or if the guy next to me is shooting an sbr....

No doubt but I have been shooting long enough to set those aspects aside. The 800x was noticeable less recoil and given that is used nearly half as much powder to get to the same velocity it was very noticeable for such otherwise similar loads. I not saying it was 38 special vs 44 mag difference but it was different enough you could have mixed the two loads in the cylinder, blindfolded me, put plugs and muff on me and I still would have been able to feel the difference in my hands shooting the two loads. The lack of muzzle flash and reduced muzzle blast was just icing on the cake.

Remember recoil is due to both the mass of bullet and the mass of the propellant being ejected out of the gun. Can't beat physics. If we get the same velocity with less mass of propellent we get less total recoil. The human body does not have the temporal resolution to feel the different in the pressure/acceleration curves of slow vs fast powder. A bullet is in the barrel of gun on the order of 1-3 millisecond depending on the gun and we just can't sense sub components of events happening that fast. We just perceive them in their totality.

Look up some of the recoil calculators they will tell you the same thing in number form.