Where do you find pressure in the recoil formula?

 

No idea if that even exists. My post is just to show how high pressure can go before the gun fails. mind boggleing to me. Recoil would be huge to say the least.

 

Recoil is a function for how heavy a payload, what velocity, and how heavy the gun. Pressure is not directly related to recoil.

 

that’s a bit simple. It is the pressure that allows a certain payload to achieve a certain velocity. So yes, in fact, pressure does create the recoil.

 

Anybody remember that article?

Looks like this is the article you're referring to:

Important Information About Shotshell Pressures | Shotgun Life

Shotshell pressures seem to be a worrisome area for many shotgunners, especially reloaders. They worry that if they shoot excessive pressure loads that their shotgun could well “blow up.” They’ve heard that from their buddies, but they really don’t have any solid scientific evidence to support...

www.shotgunlife.com

 

Even so. He’s equating pressure to recoil too. ‘tain’t so McGhee. Look through the charts. Find loads traveling at equal velocities but vastly different pressures. Same charge weight. Their recoil is the same. Put 18 gn of Red Dot behind 2 ounces of #6. Velocity will be waaay down but pressure will be waaay up compared to the 18 gn behind an ounce. Recoil may be a bit higher but it isn’t a result of pressure.

 

The pressure builds before the shell opens. This pressure is exerted against all sides of the shell, then consequently the chamber itself. Since the crimp is the weakest "wall", as soon as the crimp opens the pressure converts to forward motion of the payload, and reward motion of the gun. The pressure is gone. It is the cause of recoil, but has no effect on the intensity of the recoil felt. Felt recoil comes from the explosion getting the payload from 0 fps to 1200 fps in a fraction of a second.

It is the same as happens with a garden hose. Hold the end closed, pressure builds in the hose. If the pressure is high enough the hose will expand. Open the end there is no more pressure in the hose, only motion. Water heading out the opening and the hose might have moved in the opposite direction depending on amount of pressure.

 

Playing the devil's advocate... The projectile is moving from breech to the muzzle because the force acting behind it is greater than the force acting in front of it. The greater that force differential, the faster that projectile will move. Can we agree on that? What do you propose to call that force and what are its units? IMHO, giving me the formula for recoil and stating that pressure is not part of it is being intellectually lazy. I want the nitty-gritty logical argument why velocity (and therefore recoil) is independent of pressure.

 

I had it explained to me in a mechanical analogy. If you keep the engine pinned at 6000 rpm it might last 500 miles. If you drive it like normal and keep everything in from 1200-3500rpm it will last for 150k. AKA it might be able to do it, but it won't be able to do it for long.

 

Peak pressure is not a part of the recoil calculation. Peak pressure is what is published in manuals and what is used for the SAMMI standards. Recoil is calculated from the velocities and mass of the ejecta and the weight of the gun.

Yes you could integrate the force on the projectile over the time in the barrel and calculate the velocity from the force acting on the projectile and the time. If you actually had an accurate force/time curve. Maybe that is possible now with pizz-eo electrical sensors. No way to get that curve measuring pressure with lead crusher pellets. And you could calculate the recoil of the gun that way too. It is going to be a heck of an integral solution or a numerical analysis problem. You should, if you do it right, get the same results either way.

I see no reason to bypass SAMMI standards for pressure just because the idiots on Mythbusters had trouble blowing up an individual gun.

Yes, I know the post was a troll. It has been a slow day for me since I must be intellectually lazy. I do find it comforting that there is a good safety margin in the standards.

 

Peak pressure is not a part of the recoil calculation. Peak pressure is what is published in manuals and what is used for the SAMMI standards. Recoil is calculated from the velocities and mass of the ejecta and the weight of the gun. Now...yes you could integrate the force on the projectile over the time in the barrel and calculate the velocity from the force acting on the projectile and the time. If you actually had an accurate force/time curve. Maybe that is possible now with pizz-eo electrical sensors not. Bet was hard to come by with lead crush pellets to measure pressure,. And I guess you could calculate the recoil of the gun that way too. You should, if you do it right, get the same results either way. You might be careful with that intellectually lazy comment if you do not understand why you do not need to measure pressure to get recoil.

I see no reason to bypass SAMMI standards for pressure just because the idiots on Mythbusters had trouble blowing up an individual gun.

So what would you call that force that causes the bullet to have velocity (yes, albeit constantly changing over its action on the bullet) and what are its units?

 

Sorry to disagree with your analysis of what would have been a howitzer-like recoil. The forces causing the barrel to blow up are no longer acting in the same direction as the travel of the bullet (no longer following Newton's law as far as the bullet is concerned). The sound may have been tremendous but I do not know if the resulting recoil would have been so.

 

I mis spoke on the recoil. I know better than that. Whole purpose was to show how much pressure the gun could take before it destructed.

 

A challenge to reloaders. If you are so inclined... Look up the reloading data using the same components and lot#s (primer, powder, wad, weight of shot, etc) under the same condition (temperature, altitude, etc.) except for the weight of the powder. Chart the resultant velocities against their pressures. Now the relationship may not be exactly linear (especially at the extremes) but it'll tend to be direct, as opposed to an inverse or no relationship.

 

"'So what would you call that force that causes the bullet to have velocity (yes, albeit constantly changing over its action on the bullet) and what are its units?"

I would call it pressure with the units of PSI or the appropriate units in the system one wants to work in.

But what you seem to be missing is the fact that the reloading manuals report peak pressure. That is the maximum value of the pressure for one instant in time. One instant in time says nothing about the whole pressure/time curve that determines the bullet velocity or the gun velocity (recoil). Imagine a whole curve of 1000 points of data and you know the value of only 1 point. What are you going to calculate from that?

Yes, the calculation you are thinking about could be done if you actually had a good pressure/time curve. Where are you going to get that? And even if you do it that way the actual results are going to be the same for recoil as calculated from mass and velocity. Both of which are commonly measured and reported.

And a gun firing follows Newton's laws all the time even if it blows up.

 

Completely aware of pressure readings inside the cartridge plotted against time from when the primer ignites the propellant to the time the projectile leaves the barrel. In fact, such graph may show optimum barrel lengths- optimum in terms of barrel length's contribution to projectile velocity. Once the pressure behind the bullet equals the pressure in front of it, pressure no longer contributes to velocity, ignoring friction. If the projectile is still within the barrel, then barrel friction will begin to act on the projectile. If the projectile is already out of the muzzle, no amount of residual pressure within the barrel will contribute to projectile velocity. Now it's in the realm of exterior ballistics; an interesting topic for another time's discussion. I have no formal training in ballistics but I have a degree in engineering, with keen interest in internal, external, and as a physician, terminal ballistic (as it applies to the human body). I agree that the only determinants of calculated recoil are ejecta weight and its velocity (within the barrel) and the weight of the firearm used. What I have difficulty accepting is when people say internal ballistic pressures (however momentarily measured or as charted in reloading data) have nothing to do with in-barrel or muzzle velocities.

 

A few years back, Bruce Bowen expeimented with loads until he blew up a cheap single shot gun.
Don't remember the specifics, but it took a lot of powder.

 

Hard to imagine what the recoil would have been like.

Probably very low, since if the chamber blew up, that means the shot/wad probably weren't leaving the muzzle at high velocity.

 

It would have been the one immediately before the gun blew up that had inordinate recoil levels. The higher pressures probably were delivering increased projectile speeds with incremental increases in recoil.

 

Posting as an innocent bystander who once had an intential overload of what was probably W540/HS6 slipped into my meatshoot vest pocket(bogus not loaded by me shell was determined by prime- I only used fed209 @time) .
‘The recoil was no different than the 3-3/4 dram equivalent 1-1/2oz of nickel #5 I typically loaded for 40plus yards behind the house in an Activ hull, but it threw flame out breach of an m870 competition, licked up the bolt in a semi-opened position, cracked support block under barrel as well as magazine tUbe And bulged reciever area at extractor cut

 

Posting as an innocent bystander who once had an intential overload of what was probably W540/HS6 slipped into my meatshoot vest pocket(bogus not loaded by me shell was determined by prime- I only used fed209 @time) .
‘The recoil was no different than the 3-3/4 dram equivalent 1-1/2oz of nickel #5 I typically loaded for 40plus yards behind the house in an Activ hull, but it threw flame out breach of an m870 competition, licked up the bolt in a semi-opened position, cracked support block under barrel as well as magazine tUbe And bulged reciever area at extractor cut

Nice friend. Wouldn't you love to know who put that shell in your vest??? Worst "trick" of that type i have ever seen is feathers.

 

It burnt the Activ hull into 2 pieces one left barrel with shot & wad, was told the target broke.
it took a rubber hammer & removal of barrel to open up gun.

 

It makes me wonder what they used in K80’s to make them blow up in such a controlled manner. Peanut Brittle can only take so much and BANG the right side of the receiver is gone.

 

I don't know anything but it makes sense to me that to measure pressure or chamber pressure you would have to set off an item like a shotgun shell in a sealed chamber with insturmentation to read the pressure in the chamber. Also seems to me to blow up a barrel which is not sealed at the muzzle would take an extraordinary amount of pressure.

Now if you want to find out how much pressure it would take to blow up a new barrel you would have to know the pressure of the shell you're testing in a new barrel. Pressure I'm guessing is caused from expansion and if you were testing heavier and heavier shells in the same barrel it wouldn't be a valid test. I'm thinking you would have to keep increasing pressures in a factory new barrel until you achieved barrel failure. Then you would have to test the same load in another new barrel to see if you can duplicate the failure with a consecutive number of attempts. But I don't really know anything about this just using my common sense. I'm also thinking if you're wondering about Krieghoff barrel performance you should have a factory Krieghoff sponsorship.

PD

 

Bruce wrung out a H&R Topper with a SP2 receiver that was suitable for 65,000 PSI metallics, with a very thick shotgun barrel. I donated some oddball wads so he could load a stupid amount of powder behind a stupid amount of shot. These guns were meant to be abused, and had a lot of low grade steel in them. An engineer at H&R told me their break-open rifle was as strong as the Ruger #1. (wow)

FYI, when Winchester made their 1200 pump, it was routinely tested to 40,000 PSI repeatedly without incident. Also, many decades ago, Winchester engineers put 2 cases (1000 rds) of Blue Pills through a Winchester Model 21 without any damage to, or change of, critical dimensions of the gun.

A Spanish Proof House tested an Antonio Zoli, now Zoli USA, to 70,000+ PSI without damage to the gun.

Nobody is saying that anyone should ever load above listed recipes, or whip up a load on a whim. Use listed loads. Not all guns have that level of idiot-proofing.

 

Bullet Ballistics 101: Pressure, Velocity & Distance

Wayne van Zwoll explains in plain terms key points of bullet ballistics, including pressure, velocity and distance.

gundigest.com