Powder choice/burn rate and recoil. How are they related, How do you predict or measure effect?

[dellet]

After a few years of ignoring them, I started shooting my single shot rifles again. Two things have happened in that time. I've gained some knowledge about loading, and I have gained some years. It did not take too many shots to remember why casual competitive shooting was too many rounds in a day.

The rifle in use is a model 1885, 45-70 that weighs in around 8 pounds. Adding to the felt recoil is a very attractive old school crescent shaped rifle butt plate.

Recoil calculators include the basics, bullet weight, velocity, charge weight and rifle weight. It seems like things such as peak pressure and muzzle pressure would also play a role at least in felt recoil, if not measurable.

Is it really as simple as all things being equal, velocity, bullet and rifle weight, less powder is less measurable recoil?

Are there characteristics in burn rates, that you could see in a graph, that would predict less pain and suffering while shooting and the amount of ice needed both on the shoulder and in the adult beverage after the fact?

The load/rifle combination is a 325 grain bullet, 2000 fps, #8 rifle and charge weights in the 48-55 grain range. Recoil is basically in the 30-40 ft lbs.

 

[Heman]

Some of my observations.

My 308 Palma laod is 44.5gr Varget with a 185 Berger the 280 Remington is 61.5gr H1000 with a 175gr SMK or 180 Hybrid. Both have recoil however the Palma rifle is a quicker smack where as the 280 is a slower nudge although not as slow as say my 45-110 or my Trapdoors or the rifled muskets. The powder used seems to have some affect on what you feel as far as the impulse, quicker powder means quicker impulse. The 308 feels like a quick punch where as the 280 is a long shove.

A lighter load does mean less recoil from a Physics standpoint if the bullet goes forward the gun goes backwards. If there is less powder to push the bullet forward you are going to have less push going backwards. Heavier rifles are going to have less recoil due to having more inertia and resisting that change in motion more. Why my prone rifles are around 13-14 lbs. Also lighter bullets have less recoil why for example in across the course shooting people will run lighter bullets at 200 for rapid sitting to get less recoil. Also why my 243 with a 105gr bullet going at 3280 has less recoil than the 280 with a 175 going at 2910ish. There is more kinetic energy at the muzzle with the 243 but way less recoil.

The other thing is rifle geometry my 308 AR10 course rifle feels like it has less recoil than the M14 when shooting the same loads. Think this is because the action is lower on the AR10 than the M14.

 

[dellet]

That introduces way too many variables for what I am trying to get an understanding of.

If you have same
Rifle
Bullet
Velocity

Two different powders/quantities

In general terms the faster powder will have a higher peak, faster drop and less muzzle pressure. In the calculators this shows less pounds on the shoulder for less time.

That would seem to indicate that peak pressure has less to do with force exerted than muzzle pressure. But the pressure curve could be an indicator of felt recoil.

This may all be part of the equation to calculate recoil force and since I just plug in numbers, can't see all the factors being accounted for.

Or maybe I need a better understanding of what causes recoil induced pain?

 

[Heman]

In a given cartridge you won't be able to have powders with different enough burn rates to test this and achieve the same velocities. If you want less recoil a.) drop your charge or b.) choose a lighter bullet. For example I can't put enough H1000 into a .308 case to get the bullet to the same speed I can with the load of Varget.

Generally pain form recoil is because you don't have the gun up against your shoulder enough to cause your body to move with the gun, i.e. your body is one with the gun. If the gun is far away the gun moves into your body and this causes a collision.

 

[dellet]

Actually I can achieve the same 2000 fps/325 grain load with as much as as a 15+ grain spread using different powders.

That would indicate possibly as much as 10% change in the calculated numbers of recoil.

That's enough to notice and enjoy the benefit from, even with perfect form and tough guy image to uphold.

 

[Heman]

Ok well there is your answer. I was just referring to the cartridges I shoot. Only way you wil know if it feels like less is to give it a try.

 

[dellet]

Knowing it happens and being able to create the effect, is not really understanding why it happens.

If I can understand how/why it happens, then it's possible to manipulate the results to an advantage.

That's the basis of the original question.

Seating depth fine tunes combustion/burn rate, so recoil can be tuned within a certain window even using the same powder/charge. That's part of the equation in searching for the best load.

In a gas gun, these same concepts can be used to manipulate port pressure and bolt speed within a certain window.

What actually causes the drop in recoil?

The pressure curve?
Muzzle pressure?
Gas volume?

 

[Laurie]

Recoil is affected by charge weight alongside any given combination of MV and bullet weight. That is because recoil matches the total energy going out the front end which is the conventional definition of muzzle energy (bullet mass and velocity) but also powder charge mass allied to velocity. Just because the charge is consumed, it is still there and exiting from the firearm but now as gas with a few solids. As energy is affected more by velocity than mass and the gases are travelling at high speed, each additional grain weight of powder increases the energy total more than an equivalent weight increase for the bullet.

All recoil calculators ask for bullet weight, MV, and charge weight, but not powder details. No doubt they do have an effect, but I believe it is marginal. Sierra Bullet's Infinity suite has a such a simple calculator. Taking your figures and with a top charge weight of 55gn as quoted but low end of 40gn (15gn range for similar performance depending on powder choice), it says:

40gn charge:

14.1 fps free recoil velocity
3.5 lb-mass / fps
24.7 ft/lb recoil energy


55gn charge / everything else the same

15.0 fps free recoil velocity
3.7 lb-mass / fps
28.1 ft/lb recoil energy

So, not huge increases, but with an English shotgun style straight buttstock and a deeply concave buttplate, any small increase in recoil speed and energy will likely be felt acutely. The shape and amount of drop in the stock can have as much effect on perceived recoil and in actual bruising inflicted as the raw physics. I have two Chilean Mauser 7X57mm service rifles, an M1895 and M1912, both 29-inch barrel long rifles. The latter with its more substantial 1898 type action will be a bit heavier overall but not vastly. The 1912 does have a better developed stock though with a pistol grip form, and firing identical loads, its perceived recoil is noticeably less. Its effects appear to be actually less too in that I am much less likely to see bruising shooting it in summer conditions with light clothing.

In any event, 28 ft/lb energy is enough to hurt badly (as you know). The rule of thumb was long that most people can happily cope with repeated shots from a heavy 308 Win load in a heavyish tactical type rifle weighing maybe 12.5 / 13 lb. That is way below what you're getting even before the edges of that deeply curved butt hit your shoulder.

 

[dcali]

It’s a conservation of momentum thing. The only things that matter are the weight of the objects flying apart and how fast they’re moving. It really is that simple.

 

[dcali]

By the way, there is a saami sanctioned method to calculate recoil on their website. It involved multiplying muzzle velocity by a firearm dependent factor (1.5, for example) to get the gas velocity. You can then calculate the rifle’s velocity, energy, etc. getting the exact powder velocity is difficult, but in the end it’s not that big a deal. It’s not like you can feel the difference between 4350 and 4895.

 

[Tommie]

Short of rebarreling to 22 Hornet, nothing’s gonna make your rifle a plinker. The thought of shooting 45-70 with a crescent buttplate makes me wince.

 

[dellet]

Here's where

Recoil is affected by charge weight alongside any given combination of MV and bullet weight. That is because recoil matches the total energy going out the front end which is the conventional definition of muzzle energy (bullet mass and velocity) but also powder charge mass allied to velocity. Just because the charge is consumed, it is still there and exiting from the firearm but now as gas with a few solids. As energy is affected more by velocity than mass and the gases are travelling at high speed, each additional grain weight of powder increases the energy total more than an equivalent weight increase for the bullet.

All recoil calculators ask for bullet weight, MV, and charge weight, but not powder details. No doubt they do have an effect, but I believe it is marginal. Sierra Bullet's Infinity suite has a such a simple calculator. Taking your figures and with a top charge weight of 55gn as quoted but low end of 40gn (15gn range for similar performance depending on powder choice), it says:

40gn charge:

14.1 fps free recoil velocity
3.5 lb-mass / fps
24.7 ft/lb recoil energy


55gn charge / everything else the same

15.0 fps free recoil velocity
3.7 lb-mass / fps
28.1 ft/lb recoil energy

So, not huge increases, but with an English shotgun style straight buttstock and a deeply concave buttplate, any small increase in recoil speed and energy will likely be felt acutely. The shape and amount of drop in the stock can have as much effect on perceived recoil and in actual bruising inflicted as the raw physics. I have two Chilean Mauser 7X57mm service rifles, an M1895 and M1912, both 29-inch barrel long rifles. The latter with its more substantial 1898 type action will be a bit heavier overall but not vastly. The 1912 does have a better developed stock though with a pistol grip form, and firing identical loads, its perceived recoil is noticeably less. Its effects appear to be actually less too in that I am much less likely to see bruising shooting it in summer conditions with light clothing.

In any event, 28 ft/lb energy is enough to hurt badly (as you know). The rule of thumb was long that most people can happily cope with repeated shots from a heavy 308 Win load in a heavyish tactical type rifle weighing maybe 12.5 / 13 lb. That is way below what you're getting even before the edges of that deeply curved butt hit your shoulder.

That makes a lot of sense.
I know that equal forces applied differently, stock angles, butt shape, will make a difference in feel. Same stock shooting off the bench vs off hand will also be different.

My mind is stuck on a champagne cork. It's all the same components, but the more you shake it the, greater the velocity and recoil. It's a gas pressure release issue.

It's possible on paper to come up with loads that peak at 38,000 psi. that uses the same bullet, same velocity. The difference being the pressure curve and duration, then finally muzzle pressure. It's possible to have the same exit velocity of the same bullet, with a greater pressure and volume of gas behind it. Slower powder.

It seems to me that the amount of pressure relief when the bullet exits, is a reasonable indicator of more or less recoil energy. At least on paper.

 

[dellet]

By the way, there is a saami sanctioned method to calculate recoil on their website. It involved multiplying muzzle velocity by a firearm dependent factor (1.5, for example) to get the gas velocity. You can then calculate the rifle’s velocity, energy, etc. getting the exact powder velocity is difficult, but in the end it’s not that big a deal. It’s not like you can feel the difference between 4350 and 4895.

I will play with that and predicted muzzle pressure through Quickload. What has the gears turning is that it really seems that gas volume, pressure and speed on exit, is what I have not given much thought to until now.

5744 feels a lot different than 335 at the same velocity in this setup

 

[K22]

handloads.com contains a recoil calculator. But the design of the stock and type of recoil pad can greatly influence felt recoil.

 

[dcali]

There’s isnt much you can do about a .45-70 since most of the recoil is coming from the bullet. You might try using the lightest powder charge that gives you the velocity you want, but I doubt you’ll feel a difference in a blind test. It’s going to be a beast no matter what. Even a brake won’t do much- again because the bulk of the recoil is coming from the bullet. That’s why brakes are so much more effective on something like a .22-250. It’s all powder, and no bullet.

 

[Laurie]

There’s isnt much you can do about a .45-70 since most of the recoil is coming from the bullet. You might try using the lightest powder charge that gives you the velocity you want, but I doubt you’ll feel a difference in a blind test. It’s going to be a beast no matter what.

Very true! I had a brief crush on the 45-70 and single-shot rifles maybe 20 years ago myself. That 'love affair' cooled rapidly and divorce occurred in about a year, the Italian repro Sharps falling-block traded in against something else. The final straw was a day testing some heavy (500gn?) commercial gas-checked lead RNLs using IMR-3031 loads from the Speer Manual's 'Cowboy Action' section, supposedly light loads. Charge were going up in (I think) 1gn steps and I could feel the recoil rise noticeably on each increase. The rifle had a tang rearsight mounted on a substantial block. The first shot with the penultimate charge saw the edge of the sight-base rip a chunk out of the joint on my thumb - so shooting stopped while a handkerchief was found and wrapped around the digit trying to staunch the flow of blood over the stock wrist, not very effectively I might add, so a right mess! Then the next shot saw the rearsight aperture disk hit my specs and knock the lens out of the frame. I think that was the point when I knew I was a wimp and that the 45-70 wasn't for me.

 

[dcali]

Very true! I had a brief crush on the 45-70 and single-shot rifles maybe 20 years ago myself. That 'love affair' cooled rapidly and divorce occurred in about a year, the Italian repro Sharps falling-block traded in against something else. The final straw was a day testing some heavy (500gn?) commercial gas-checked lead RNLs using IMR-3031 loads from the Speer Manual's 'Cowboy Action' section, supposedly light loads. Charge were going up in (I think) 1gn steps and I could feel the recoil rise noticeably on each increase. The rifle had a tang rearsight mounted on a substantial block. The first shot with the penultimate charge saw the edge of the sight-base rip a chunk out of the joint on my thumb - so shooting stopped while a handkerchief was found and wrapped around the digit trying to staunch the flow of blood over the stock wrist, not very effectively I might add, so a right mess! Then the next shot saw the rearsight aperture disk hit my specs and knock the lens out of the frame. I think that was the point when I knew I was a wimp and that the 45-70 wasn't for me.

Sounds about right!

 

[dellet]

Honestly this has become an excercise in learning. I tried a new powder that has been extremely accurate in other cartridges and found load data for 45-70. The draw back is that it has always taken more powder to get less velocity. I was a bit surprised to find data for both LT-30 and 32.

LT-30 seems to have more recoil than 4895 in this application. All things considered it could have been the order I shot them in.

If you can believe all the load data and calculators, 5744 should be the softest shooting powder, if it all boils down to powder volume.

Shooting antiques has a special appeal, but honestly it loses something shooting replicas with smokeless. Something about a 50-70 in a 16” Calvary carbine with a 500 grain bullet, is flat out fun. Maybe part of it is the noise and smoke

 

[dcali]

There is some interesting discussion of felt recoil here: http://kwk.us/recoil.html

 

[dellet]

There is some interesting discussion of felt recoil here: http://kwk.us/recoil.html

Interesting to be able to compare with the provided models. Looks like depending on powder selection, I would have a comparable experience shooting either a 7RM or a 338 Winchester.
To get the full effect I might need to ditch the modern stock and mount either one of those to a 2x4 and use a claw hammer head for a buttplate.

This has been helpful and I appreciate the input.