It would be an interesting test to take a few cases and fire them dry with about .005 headspace 3 times and measure the thickness at the web versus the same number of cases with the same .005 headspace, but lubricated. I'd have to section them as I don't have the tools to measure thickness at the web.
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Known Loads too hot now..why
- Thread starter clhman
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I think water on cases and in chambers is a non issue. Firearms can be shot under water without ill-effects.
He has never answered if all loading componeents were of the same lot
bigngreen
Well-Known Member
A little recap! Plus the third rifle was shooting factory loads.
We have 2 cartridges loaded at or near top end of the pressure range and factory 22-250 (lots of case taper) which I'd assume to be loaded fairly warm, and none of these rifles had ever exhibited these signs before. The only thing they had in common was everything was wet. When my back heals up I guess I'll sacrifice some brass to gain some knowledge.lightbulb
Could you use 7mm WSM brass? Neck it down to .277 with your resizing die, and set the shoulder back to a snug headspace fit at the same time. My LoadBase 3.0 ballistic software shows a case head to shoulder measurement of 1.702" for 7mm WSM brass, versus 1.664" for both the 270 WSM and 300 WSM. If the 7mm WSM brass is ~0.038" longer from case head to shoulder, then it seems like this approach would also work. But it you can easily reset chamber headspace, that should cure the headspace problem also.
Differences in the brass life you described could be both in the properties of the brass (softer versus harder), the production headspace measurements of the brass, and even the friction coefficient of the case surface.
The effective differences between slicker than snot (low friction coefficient) brass/chamber interfaces and rough (high friction coefficient) brass/chamber interfaces - as related to case head thrust and case head separations - are as follows:
The slicker the surface the more the cartidge case head and sidewalls are able to slide back towards the bolt face. After they are set back firmly into the bolt face, the brass that then blows out to conform to the chamber dimensions is the thinner brass located at the shoulder area. This thinner brass can blow outwards in a gentler manner because the expansion of the brass is spread out over a larger surface area of the casing. ALSO, the brass in the shoulder area has been annealed, and it is able to stretch to fit with less chance of tearing than the harder brass back in the case web area. Little harm is done to the casing. And the case head strikes the bolt face with greater force.
With a rough, unlubricated, high friction coefficient case/chamber interface, the forward portions of the case wall are blown out and tightly grip the chamber with. So firmly that the forward portions of the case wall are locked to the chamber - immobilized. Tremendous pressures are generated and blow the case head back into the bolt face. The forward side walls are immobilized yet the case head is moving back into the bolt face. Something has to give. The brass yields just forward of the case head, where case web stretches (permanently thinning) and case head separations occur.
The reason the brass stretches at this location is because this is the first location moving from the shoulder toward the case head where the case wall thickness becomes rigid enough to prevent its being pressured out and locked onto the chamber walls. The thinner case wall is easily pressured out with enough force to tightly grip the chamber. At the case web, the web thickens to the point that the pressue isn't sufficient to lock the web onto the chamber. This is first location where the brass is able to shift/move along the chamber. So this case wall thins out at the location where it's too thick to bond to the chamber, and too thin and weak to survive the tensile force trying to stretch it apart.
Lastly, how does this stretching of the case web area reduce case head thrust (force) against the bolt face? The case wall stretches at a location where is starting to get thick. A fairly substantial tensile force is required to stretch, thin, and permanently deform this thickened case web. And this tensile force is restraining (trying to pull the case head away from bolt face. It's not a strong enough tensile force to prevent case head setback, but it is substantial enough to reduce case head thrust.
So if you want to accelerate case head separations and reduce case head thrust, roughen up your chamber to increase the coefficient of friction between the case & chamber. (Don't really do this!)
If you want to slow the progression of case head separations and increase case head thrust, polish your chamber and lube your casing exteriors to reduce the coefficient of friction. BTW, this is what we all should want. The lugs on the bolt are designed to survive the additional case head thrust against the bolt face. The brass is the weak link, and the component that needs the tender loving care.
Hope this helps provide a better, conceptual understanding. If you understand these consepts, you will be better able to toubleshoot and resolve issues related to case head thrust/setback, case web stretch, and case head separations.
Back to the reloading room...
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The only person that could demonstrate this one way or the other to your satisfaction, would be you. If it's not a problem for you, then it truly is a non-issue - for you.
I haven't really experienced problems hunting in the rain or melting snow over the years.
I am convinced case head thrust will be increased to some extent with a low friction case/chamber interface compared to a high friction case/chamber interface. Such that if one loads case pressures to the very brink of case head brass flow with a higher friction case/chamber interface, that those same loads with a lower friction case/chamber interface could result in noticably increased and objectionable brass flow and stiffened bolt lift.
The part about firing a high intensity rifle submerged under water without ill-effects? If that's your contention, what's your definition ill-effects? I'd like to see this one on Myth-Busters.
Sloping cases have more bolt thrust than cases with less body taper, P O Ackley proved this years ago. Of course any lubrication on a case will have more bolt thrust, that is a given. You even stated ealier in this thread that as long as SAAMI spec pressures are not exceeded that all is fine.
Episode 51: Myths Reopened
•You can fire a bullet from a rifle or handgun underwater: confirmed. A 9mm or .357 magnum would be lethal at 2ft.
Here is another test of firing a pistol under water
Some Comments on Shooting Underwater
What would happen if someone fired a rifle underwater? Would the pressure produced rupture the gun? It is assumed under these conditions that the barrel and action are completely submerged and the barrel is full of water.
To get an answer to this question the NRA performed a number of underwater experiments. In the first experiment the bullet and powder charge were removed from a .45 ACP cartridge and the primer flash hole was covered with a waterproof disk to keep water out of the primer. The gun was loaded with the primed cartridge and held vertically while the barrel was filled with water. Without changing the gun position the gun was fired. There was the sound of a mild 'splat' as the water was blown up against the ceiling. The gun was not damaged.
Next the gun was loaded with another primed cartridge and the fully submerged gun was fired. No noise could be heard, but a spurt of black water was ejected from the muzzle of the gun for a distance of about one-foot. Reassured that the gun mechanism would work underwater, the gun was loaded with a Service ball cartridge and fastened in a heavy vice on the bottom of a tank. The tank measured 40"x24"x24" and was filled with water. Care was taken that the barrel was filled with water and had no air pockets. On firing (by remote control) there was a lot of disturbance and quite a bit of water splashed out of the tank. The bullet passed through 16" of water, a 7/8" pine board, 6" more of water and finally came to rest against a second board after making a deep dent in it. The empty cartridge was not ejected, but jammed with the pistol slide part way open and the cartridge caught in the ejection port. The pistol was not damaged in any way.
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Buffalobob
Well-Known Member
The dynamic viscosity of water versus oil at ambient temperatures, not internal engine temperatures, is about a factor of five difference. This is why it will provide more bolt thrust than an oiled chamber. If you take Varmint Als calculations and guesstimate where bolt thrust would be with water you easily get into the areas where he says it is not possible to go. You then do not need to be over pressure to get heavy bolt lift.
Shorter barreled, lower operating pressure revolvers/pistols is most plausible.
Did they fire any 60,000 -65,000 psi rifles with 30 inch barrels full of water with no ill-effects?
If so, what is the definition of ill-effects? Ill-effects on the firearm? Ill-effects on the shooter?
Here is a rifle shot under water
The experiment was continued with a .30-'06 Model 1903A3 Service rifle with the stock removed. The rifle was clamped in a vice on the bottom of a tank and loaded with an M2 Service round containing a 152-gr. bullet. Since there was only 6" of space between the muzzle and the inside of the tank no attempt was made to place anything inside the tank to measure penetration. However, four soft pine boards 7/8" thick were placed outside the end of the tank and in line with the rifle barrel.
When the gun was fired (by remote control) the bullet penetrated 6" of water, the 3/64" steel tank wall, all four boards and lodged in a solid oak plank used as a backstop. The bolt could not be opened by hand, but opened easily to a few light taps with a rawhide hammer.
The cartridge case, just in front of the cannelure had expanded by about .032 inches and the primer pocket had opened up from the standard .209-inches to .228-inches. The primer was punctured and a small quantity of black smoke was observed to escape from the surface of the water, near the breech, when the gun was fired. The case and primer pocket expansion was greater than those usually seen when a 70,000 p.s.i. high pressure test load is fired from the same type of gun, so the pressure was probably much higher than the 70,000 p.s.i.
The rifle bore, full of water, would contain about 385 grs. of water, which is equivalent to adding 2.5 times the normal bullet mass that the powder pressure has to move. In spite of this additional resistance from the water, the rifle showed no bulging of the barrel or other damage
While this limited test is interesting and gives you some idea what may happen it is not definitive. The results could be different if the same test were performed with a higher intensity cartridge or one of the magnum cartridges with large case capacity.
The experiment was continued with a .30-'06 Model 1903A3 Service rifle with the stock removed. The rifle was clamped in a vice on the bottom of a tank and loaded with an M2 Service round containing a 152-gr. bullet. Since there was only 6" of space between the muzzle and the inside of the tank no attempt was made to place anything inside the tank to measure penetration. However, four soft pine boards 7/8" thick were placed outside the end of the tank and in line with the rifle barrel.
When the gun was fired (by remote control) the bullet penetrated 6" of water, the 3/64" steel tank wall, all four boards and lodged in a solid oak plank used as a backstop. The bolt could not be opened by hand, but opened easily to a few light taps with a rawhide hammer.
The cartridge case, just in front of the cannelure had expanded by about .032 inches and the primer pocket had opened up from the standard .209-inches to .228-inches. The primer was punctured and a small quantity of black smoke was observed to escape from the surface of the water, near the breech, when the gun was fired. The case and primer pocket expansion was greater than those usually seen when a 70,000 p.s.i. high pressure test load is fired from the same type of gun, so the pressure was probably much higher than the 70,000 p.s.i.
The rifle bore, full of water, would contain about 385 grs. of water, which is equivalent to adding 2.5 times the normal bullet mass that the powder pressure has to move. In spite of this additional resistance from the water, the rifle showed no bulging of the barrel or other damage
While this limited test is interesting and gives you some idea what may happen it is not definitive. The results could be different if the same test were performed with a higher intensity cartridge or one of the magnum cartridges with large case capacity.
clhman
Active Member
Myth-Confirmed!
Since I started this, I can end thisgun).
It's confirmed. Water=bad.
Today I went out to the range and shot the same ammo that was way too hot on Thursday. Absolutely nothing different. I don't know how to post an image, but my first 2 shots went in the same hole. I couldn't even measure it because I wasn't able to distinguish 2 separate centers.
The exact same ammo I shot showed zero signs of pressure today. No shiny spot, no hard bolt. I shot another group of 2 and again put them in the same hole. I shot once more to be sure for a total of 5 shots. I observed no pressure signs whatsever. The temperature was about 42 degrees. (10 degrees warmer than Thrusday - so technically my loads should have been hotter.)
I'm definitely not an engineer or ballistician but I can tell you I'm thorough and make sure that I test the exact same and science aside, there was a huge difference today that only can be explained by the moisture.
I didn't chrono them or even clean my gun to not skew the test.
Thank you all for your responses, this has definitely taught me a lesson.
clhman
Since I started this, I can end thisgun).
It's confirmed. Water=bad.
Today I went out to the range and shot the same ammo that was way too hot on Thursday. Absolutely nothing different. I don't know how to post an image, but my first 2 shots went in the same hole. I couldn't even measure it because I wasn't able to distinguish 2 separate centers.
The exact same ammo I shot showed zero signs of pressure today. No shiny spot, no hard bolt. I shot another group of 2 and again put them in the same hole. I shot once more to be sure for a total of 5 shots. I observed no pressure signs whatsever. The temperature was about 42 degrees. (10 degrees warmer than Thrusday - so technically my loads should have been hotter.)
I'm definitely not an engineer or ballistician but I can tell you I'm thorough and make sure that I test the exact same and science aside, there was a huge difference today that only can be explained by the moisture.
I didn't chrono them or even clean my gun to not skew the test.
Thank you all for your responses, this has definitely taught me a lesson.
clhman
Good deal. What brand of brass are you using?
Did you fire the .22-250 also? The factory rounds.
If you really want to convince us, you'll need to dunk your cartridges in some water the next time you shoot on a dry sunny day!
Then tell us if you get pressure signs
Did your rifle shoot poorly the other day with water in the chamber? I'm not sure why is would have. Same internal pressure levels. Just additional pressure signs.
Did you fire the .22-250 also? The factory rounds.
If you really want to convince us, you'll need to dunk your cartridges in some water the next time you shoot on a dry sunny day!
Then tell us if you get pressure signs Did your rifle shoot poorly the other day with water in the chamber? I'm not sure why is would have. Same internal pressure levels. Just additional pressure signs.
clhman
Active Member
No I only shot the SAUM. It is what I'm trying to focus on now. It is just R-P brass.
Yes it shot poorly, but it is a new gun to me, so it might have been user error.
Did you get to shoot at 1000yds? Where do you shoot? Just off the highway?
I don't know if I'll be wetting my cartridges any time soon. I think I've learned my lesson...
Yes it shot poorly, but it is a new gun to me, so it might have been user error.
Did you get to shoot at 1000yds? Where do you shoot? Just off the highway?
I don't know if I'll be wetting my cartridges any time soon. I think I've learned my lesson...
