Thread: The Maths of Recoil

I've been contemplating lightweight rifles. The downside being increased felt recoil. So the question is do efficient cartridges that achieve good velocity with smaller powder charges have less measured recoil than a cartridge burning more powder to achieve the same velocity ?
Newtons third law does not consider the rocket effect of burning gases or the weight of the gasses (propellant) that are also accelerated.
https://www.google.co.nz/url?sa=t&rc...FdNwGLZlwyk2Wx

my brain (& shoulder) associate more felt recoil with light weight rifle + heavier projectiles + pushing said projectile fast. Not sure that necessarily translates to more or less powder ? Different cartridges within similar case capacity for same calibre can produce quite different felt recoil from my expereince. eg 280 vs 284

Originally Posted by Mauser308

Stock design and angles equate just as much if not more than the physics as well. A crap stock that doesn't fit you will punish you. Comparatively a well-fitted stock tames even the worst recoil forces, some african big game rifles with big pills that are renowned for their recoil yet get a well fitted one is nice to shoot.

Supressors do a fair bit to slow the generation of felt recoil as well, instead of a punch you get a heavy push which is much nicer to work with.

Don't disagree with what you have written, but a cartridge that produces less recoil to start with for a given performance is going to end up better with the same good stock.
A suppressor or a break divert gas and reduce the rocket effect of the burning / accelerating gas which we feel as recoil. So it is not just Newtons 'equal and opposite forces' at play

Originally Posted by Moa Hunter

I've been contemplating lightweight rifles. The downside being increased felt recoil. So the question is do efficient cartridges that achieve good velocity with smaller powder charges have less measured recoil than a cartridge burning more powder to achieve the same velocity ?
Newtons third law does not consider the rocket effect of burning gases or the weight of the gasses (propellant) that are also accelerated.
https://www.google.co.nz/url?sa=t&rc...FdNwGLZlwyk2Wx

Greetings Moa Hunter,
I've read in the past that the recoil generated by the powder gasses can be calculated by using the powder charge and a velocity of either 4,000 or 6,000 feet per second. I will try to find the reference. The rocket effect is included in this.
Grandpamac.

Originally Posted by grandpamac

Greetings Moa Hunter,
I've read in the past that the recoil generated by the powder gasses can be calculated by using the powder charge and a velocity of either 4,000 or 6,000 feet per second. I will try to find the reference. The rocket effect is included in this.
Grandpamac.

Greetings Again,
I had a quick look through the formula you attached but to answer your main question Yes cartridges that produce the same velocity with less powder do produce less recoil. They do this, not due to some magic efficiency but due to less case volume. They also generate higher pressure. The rocket effect of the burning gasses is due to the mass of the powder charge and its velocity and nothing else. I see that the formula gives an approximation for powder gas velocity as 1.75 times projectile velocity. The formula should give you a raw figure for comparison assuming all else is equal which as we know seldom is.
I would ignore the section on metric units as it is outdated. Unfortunately Americans are profoundly ignorant on metrics and it often shows.
Regards Grandpamac.

I've wondered, now you can't have semi centrefires, would a straight skeleton stock arrangement built around a bicycle saddle spring stem give more pleasant recoil experience? Might even feel semi.

I found this link one day i was looking into it. It seems pretty similar for same bullet weight and speed to weight of the rifle. Its not a perfect table but it gives an indication.

https://www.chuckhawks.com/recoil_table.htm

From caliber to caliber i forgot to mention.

Originally Posted by grandpamac

Greetings Again,
I had a quick look through the formula you attached but to answer your main question Yes cartridges that produce the same velocity with less powder do produce less recoil. They do this, not due to some magic efficiency but due to less case volume. They also generate higher pressure. The rocket effect of the burning gasses is due to the mass of the powder charge and its velocity and nothing else. I see that the formula gives an approximation for powder gas velocity as 1.75 times projectile velocity. The formula should give you a raw figure for comparison assuming all else is equal which as we know seldom is.
I would ignore the section on metric units as it is outdated. Unfortunately Americans are profoundly ignorant on metrics and it often shows.
Regards Grandpamac.

Yes I had firstly reached the same conclusion, the weight of the propellant being added to the projectile as what we are accelerating.
The second conclusion being that if I am going to build a light carry rifle for the future it should be on a Kimber or small ring CZ action and chambered in 6.5 x 47 with a short barrel
It is interesting to consider the propellant and recoil impulse when comparing rifles. Some calibres just feel easier to shoot than others in the same weight of rifles with the same weight projectiles doing the same speed

Originally Posted by Cordite

I've wondered, now you can't have semi centrefires, would a straight skeleton stock arrangement built around a bicycle saddle spring stem give more pleasant recoil experience? Might even feel semi.

Attachment 147388

NO Sorry @Cordite it wont work! Why you ask? Because she and hers will bring in a law where by you will have to wear lycra to shoot it...and I aint doing that...leave the fish cakes out on the road ah.....(why fishcakes? cause thats what they look like after you hit one)

For one or two shots while out hunting i would not stress about how much you get beat up, can always use a slip on recoil pad when sighting in, Bit different if you decide to use it on a culling mission way more important aspects in a build

so a for example..150grn projectie going at 2500fps
we have many options to do it...
given same weight of rifle theoretically recoil SHOULD be the same.

the rocket gas effect.......now add in barrel length to equation a 30'' barrel which poked that 150grn projectile at 2500fps will have less blast than a 14'' barrel doing the same.....reguardless of amount of powder used BECAUSE it will be completely burnt before projectile exits.

Ive heard this same argument countless times with shotguns.....folks saying a 20ga recoils less than 12ga or vice versa...if both have 1 1/4oz payload and both weight 7lb..... if velocity is same so will be the recoil.
the ONLY other factor is amount of squeeze payload has when entering barrel.

biggest difference with top example is the noise will be further from ears so will seem less violent. longer barrels are definitely quieter, perceived recoil will be less even if measured felt recoil isnt.

Originally Posted by Micky Duck

so a for example..150grn projectie going at 2500fps
we have many options to do it...
given same weight of rifle theoretically recoil SHOULD be the same.

the rocket gas effect.......now add in barrel length to equation a 30'' barrel which poked that 150grn projectile at 2500fps will have less blast than a 14'' barrel doing the same.....reguardless of amount of powder used BECAUSE it will be completely burnt before projectile exits.

Ive heard this same argument countless times with shotguns.....folks saying a 20ga recoils less than 12ga or vice versa...if both have 1 1/4oz payload and both weight 7lb..... if velocity is same so will be the recoil.
the ONLY other factor is amount of squeeze payload has when entering barrel.

biggest difference with top example is the noise will be further from ears so will seem less violent. longer barrels are definitely quieter, perceived recoil will be less even if measured felt recoil isnt.

The powder turns into gas which has the same mass so still produces recoil based on its mass and velocity. A rifle with an extra long barrel is nicer to shoot as the blast is less due to slower powder gas velocity but the projectile velocity will be higher giving more recoil. The rifle will also be heavier reducing the felt recoil. Also stock shape and fit has a massive effect on how we feel recoil. Along with the laws on conservation of energy there is one saying that matter can not be created or destroyed. It is merely changed to a different state. Enough theory for one day. 6th Form Physics never seemed so far back.
Regards Grandpamac.

I specifically kept velocity and projectile weight the same..... definately agree longer barrels are MUCH nicer to shoot.

You people make it hard - more bang juice= bigger bang = more recoil. Equation solved, now off to go find a life.......