#### Clark

##### Well-Known Member
I am amazed to see the great 1990s gun forum poster Louis Boyd show up alive in 2017.

My father made a parabolic taper hydraulic system for recoil in the 1950s on the M55 contract.
The equation shows up much later in a different gun

He was using this book
https://www.amazon.com/dp/B016FU7YBG/?tag=lrhmag19-20
Hayes Elements of Ordinance.
The math in that book is senior engineering or graduate level, but the center of the mass of the gas contribution to momentum is jr. high math. It is 4,000 fps.

#### TracySes23

##### Well-Known Member
I created this Excel file several years ago.

Input the weight of the rifle, bullet and powder charge, add the bullet velocity, stir well and it spits out the ft-lbs of recoil.

Thanks Len,

I'm a fan of your "Recoil Calculator". It was interesting to discover the recoil of my 17.5 pound Bench Rifle chambered for 22-250 has between 2.6 & 3.5 ft/lbs recoil depending on which bullet I choose.
It appears as though the next column to the right calculates 500 yard energy in ft/lbs. Would I be correct in my assumption?

#### Len Backus

Staff member
Thanks Len,

I'm a fan of your "Recoil Calculator". It was interesting to discover the recoil of my 17.5 pound Bench Rifle chambered for 22-250 has between 2.6 & 3.5 ft/lbs recoil depending on which bullet I choose.
It appears as though the next column to the right calculates 500 yard energy in ft/lbs. Would I be correct in my assumption?
It's been a long time but I think that is intended as to be at the rifle, so zero yards.

#### joep17

##### Well-Known Member
Great work Len
Whatever.
We all want info and data to help us get better.

#### joep17

##### Well-Known Member
I tried to quote something else and the result might not be read correctly.

I really like the info Len put forward. The quote I wanted was the other gentlemans complaints.

#### DMP25-06

##### Well-Known Member
I have just found this thread , and I say " Thank You , Mr. Backus ."
By just opening your chart , one can quickly find a comparable rifle weight , cartridge , bullet , and velocity combination that is near their preferred rifle , and , at a glance , get a close approximation of the foot-pounds of recoil energy that will be generated , and received into your shoulder after pulling the trigger .

thanks.

#### Michael O'Connor

##### Well-Known Member
Sorry, I don't know.
Depends on the weight of the powder. That is part of the equation.

#### JASmith

##### Well-Known Member
Powder gases can add 20-40 percent or more to the recoil, depending pn bullet weight, mass of powder and so forth. Spreadsheet estimators tend to include a contribution that includes the weight of the powder and a factor of about 1.5 times the bullet velocity to estimate the gas contribution.

That estimate is almost always close enough that the shoulder won't know the difference!

There is at least one estimator, however, that refines the gas contribution by allowing an adiabatic expansion of the charge to estimate the front velocity of the expanding gas column and then runs a linear distribution of the velocity to get the momentum contributed by the gas.

One can play with the estimator here: http://shootersnotes.com/calculator/velocity-estimator/.

Use one of the sample cartridges to start. The recoil button is on the input page and one can choose rifle weight to see how that contributes to ft-lb of recoil.

Last edited:

LRH Team Member
Thanks, Len!

#### IdahoHunter208

##### Well-Known Member
I created this Excel file several years ago.

Input the weight of the rifle, bullet and powder charge, add the bullet velocity, stir well and it spits out the ft-lbs of recoil.

Wow this is very helpful. Thanks a bunch!

#### Clark

##### Well-Known Member
One might try to calculate the threshold of recoil pain. I have found the skin nerves to feel pain at ~20 psi.
To get from rifle movement in foot pounds of rifle recoil, MV, or V to calculating psi on the skin takes some doing. One needs to know:
1) the area of the recoil pad
2) the bulk modulus of the recoil pad
3) how well the shape of the shoulder fits the shape of the recoil pad.
4) bulk modulus of the shoulder [easier on fat guys]

I have been through this, but you don't need a calculator to know your win 94 30-30 narrow hard butt makes more pain than your 338WM with the large Limbsaver grind to fit, with no grinding done.

#### JASmith

##### Well-Known Member
Clark,

Excellent insight -- indeed, one can truly say "Why didn't I think of that?"!

If I understand your point correctly, the pressure comes from the contact area between the shoulder and what's hitting it combined with the recoil energy and how bar the rifle digs into the recoil pad, clothing and shoulder muscle/fat. That means that a thick, soft pad works better than a thin, stiff pad and a lot better than no pad.

Carry that to an extreme, however, and the scope meets the forehead with a lot less padding and almost no area. The result is the infamous Weatherby eye!

The fact that the work and energy are equivalent explains why recoil energy is the most common metric when comparing cartridges and rifle weight.

Momentum. on the other hand helps define muzzle rise while important, is not the source of most peoples' recoil challenge.

#### IdahoHunter208

##### Well-Known Member
I created this Excel file several years ago.

Input the weight of the rifle, bullet and powder charge, add the bullet velocity, stir well and it spits out the ft-lbs of recoil.