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Troll type question on reload pressure.

3019 Views 43 Replies 21 Participants Last post by  Chichay
I sometimes wonder if the pressure limits on reloads are more for the shooters comfort than their safety. Case in point: sometime back i remember reading am article (on here i think) about someone reloading an 870 Remington pump in increments until it blew up. Was a controlled professional experiment i believe. They were in excess of 50,000 psi when it finally blew up. Tried to find the post but had no luck. Hard to imagine what the recoil would have been like. Shooting a 105 howitzer from the shoulder maybe. Just a food for thought, nothing more. Anybody remember that article?
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Anybody remember that article?
Looks like this is the article you're referring to:

 

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My post is just to show how high pressure can go before the gun fails.
To me this post sounds like it could send wrong signals to new reloaders!!!!

Your post does not take into account the thousands of rounds shot out of the same gun with pressures above the Max allowed for your shotgun. Each shot slowly causing metal fatigue on your barrel. Until the barrel finally blows up in the hands of this reloader, and 4 other unsuspecting shooters next to him!!!

So I'd like to say please to all reloaders out there. You have to follow published data when reloading. I say keep your pressures between 9,000 psi and 10,000 psi. Well, you may want to shoot a few at 10,500 psi for your Annie loads if need be? But you don't need this kind of pressure all the time. You only need it for a small percentage of your shooting.

Yes, I agree that most shotgun barrels are built to take some very extreme high pressures before they blow. But, there is no way to know how much damage has been done to a barrel after shooting just one box of 25 shells at 16,000 psi??? How many normal loads are now needed before this barrel blows-up??? Will this barrel still function properly for the remainder of its life-span? Would you want to buy this used barrel down the road?

To sum this post up. Everyone I have seen conduct tests like this. Made sure the barrel was destroyed at the end of the tests!!! So no unsuspecting shooter would ever use it!!!! break em all jeff
 

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

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.
 

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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.
 

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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.
 

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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.
 
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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.
 

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Discussion Starter · #12 ·
Looks like this is the article you're referring to:

This is the information as i remember it but keep thinking there was a video of the blow up. Appeared the chamber also blew up and was the center of the video account.
 

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I sometimes wonder if the pressure limits on reloads are more for the shooters comfort than their safety. Case in point: sometime back i remember reading am article (on here i think) about someone reloading an 870 Remington pump in increments until it blew up. Was a controlled professional experiment i believe. They were in excess of 50,000 psi when it finally blew up. Tried to find the post but had no luck. Hard to imagine what the recoil would have been like. Shooting a 105 howitzer from the shoulder maybe. Just a food for thought, nothing more. Anybody remember that article?
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.
 

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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?
 

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Discussion Starter · #15 ·
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.
 

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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.
 

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"'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.
 

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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.
 
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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.
 
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