Shooting "proof rounds"

[Jim Watson]

I am proposing a nominal cartridge that has no "proof" loads as the nominal load is filled to the brim with powder. Every cartridge would have no wasted space.

That only works with black powder.
There are dozens of different smokeless powders with different burning rates and densities.
Example: There was once in this area a semiliterate with a reloading press. The numbers on the cans and in the books meant nothing to him. If it said "Pistol Powder" he figured it was ok to fill a pistol cartridge up with it. Likewise anything labeled "Rifle Powder." After he was on his third .300 Win Mag, my friend at the store realized this and would thereafter sell him only H870 for his Rifle Powder and 4227 for Pistol Powder. The which case full loads would not wreck any more guns.

But the only gun ever blown up on our range was almost surely a double charge of Bullseye in a .357 Magnum. It would not have held two loads of 2400.

A standard load of Unique in 9mm is a compressed load, mashed down by seating the bullet. You can hardly see a normal charge of Titegroup down in the bottom of the brass.

You could readily come up with a 100% load of some powder for some given cartridge case. But it would only apply for the one instance. Lots of other powders on the market that the factory or the handloader could use.

Anyhow, if there were no room for a 30% overload for proof, how would you test the gun for its safety margin? As is required by law in most countries but the USA.

 

[P0832177]

The idea of taking something to an extreme is one thing, using loading information from established sources. The idea of a regular diet of proof rounds is utterly without any sense of merit. Why beat the gun? The safest course is to stay within established parameters. :banghead:

 

[Ivy Mike]

I guess what I'd like to see is a cartridge that make the most of its potential. Since proof rounds are loaded with an additional 30% charge, it "proves" (pun intended ) that there is extra room in a normal cartridge for more powder. Why not use this every day with a gun designed to handle it?

Flechette, these rounds are making the most of their potential. Did you not read when owen explained about diminishing returns? You've got to balance case volume and bullet weight against the type of powder you're using. While you might be able to squeeze a bit more out of a certain round, you're not going to do it safely with any gun chambered for it. Even if you manufacture a gun that can handle it, you're not going to see much benefit from your overloaded labor.

You'd still be better off just getting a bigger round.
To use the 10mm as an example, its a great round, but overloading it is stupid. You can out perform any 10mm no matter how hot its loaded, simply by buying a .44mag.

If all you want to do is burn off powder, I'm sure you can find a more entertaining way to do it. I recall some crazy gent making a bowling ball mortar out of a piece of old sewer pipe. It used quite a bit of black powder and made a phenomenal boom by all reports.

 

[Fletchette]

Ok, I've been away for a little while. Let me make sure people understand me:

***I have no intention of shooting "proof" rounds in a store-bought gun***

So, don't worry about that...

What I AM trying to do is understand if there is any room for improvement, possibly to be used in a new gun design. That is why I am asking about all the details of accelerating a bullet to its peak potential.

I originally posted this thread after reading an old Hornady reloader's guide that had data on "hot" loads. Several .357 loads were footnoted "for Ruger only". It looks to me that these loadings were roughly equivalent to .357 "proof" loads, and the guide insinuates that only the Ruger revolvers were stout enough to handle it. This got me thinking about designing guns specifically for high-pressure loads, much like the example of the Bren Ten.

Velocity comes from the area beneath the pressure curve, guns exploding come from peak pressures.

The problem with using that "extra" space is that it isn't always extra. Smokeless powder burning rates increase proportionally with pressure. Increasing the amount of powder in a lot of cartridges will exponentially boost peak pressures because of the compounded effects of more propellant and less space - resembling an explosion more than a steady burn.

This is a good point. If I recall correctly, this was the original theory to "Magnum" calibers; traditional revolvers gave a short, high-pressure kick to the bullet, whereas "Magnums" were intended to continue accelerating the bullet down the barrel.

However, even "Magnum" loads have empty space in the cartidge. I understand that this space is needed to absorb some of the initial ignition and thus reduce peak pressures, but I was thinking that there must be another way to accomplish this end without the empty space.

 

[Jim Watson]

However, even "Magnum" loads have empty space in the cartidge. I understand that this space is needed to absorb some of the initial ignition and thus reduce peak pressures, but I was thinking that there must be another way to accomplish this end without the empty space.

Unfortunately, it is possible to "understand" things that are not so.
The reason the magnum revolver cartridges are longer than "specials" is so they will not go in a gun not meant for the high pressures. There are powder + bullet combinations that give a case full of powder at least up to the base of the bullet and sometimes compressed. The factories seldom use them because if they save a couple of grains of powder per cartridge over several million, it starts to make a difference in their costs. So they use a powder that will give the velocity they want at a pressure within the specifications at the lowest cost. And leave empty space.

I don't know how old that Hornady guide was but if you look at a new one, you will not likely find such loads in calibers already operating at high pressure. There are still things like Ruger-only .45 Colt loads, but even those are regularized now. The powder and bullet companies now have pressure test barrels, SAAMI standards, and lawyers. So things are a lot more standardized now than when they just loaded them up to whatever they thought the guns would stand.

 

[JesseL]

You may be interested in some of experimentation done by the likes of Dick Casull on duplex and triplex loads. The idea was to build a load with powders of different burning rates arranged in stages in an effort to fill in the dips in the pressure curve as the bullet traveled down the barrel.

Note: Don't mess with this kind of load if you value your life or limbs.

 

[michael_aos]

.44 Russian => .44 SPL => .44 magnum

=> .444 Marlin?

Mike

 

[Jim Watson]

I remember reading about the early Casul triplex loads. They were nearly as good as what you can do with a good stout load of newer powder like H110.

No, Mike, .444 Marlin is not just a lengthened .44 Magnum. It has a little taper and a larger head size than the revolver cartridges.

 

[michael_aos]

I think this is a related question...

I've got a couple of new-manufacture S&W 38 Specials. Only one is marked +P, but they're both rated +P according to the S&W website.

A Model 64 and Model 67. Both relatively heavy stainless-steel K-frames.

Shouldn't I be able to (safely) load these .38's up to .357 pressures if I wanted to?

Mike

 

[Ivy Mike]

Well Flechette, you can always build a bigger, beefier gun with a longer barrel.

Problem is that you still can't beat a bigger cartridge. While you could stuff a .357 case full of the hottest powder you can find in an attempt to maximize potential, you're going to need a gun that can take the punishment and enough barrel so you don't shoot unburnt powder from the muzzle.

at that point, just use a different cartridge with a gun that can take the punishment.
You may have maximized the potential of a certain caliber, but in order to build a gun to withstand the punishment, you're going to make a firearm that is going to lose its usefullness. A larger gun for a different caliber will outperform your beast with ease.

 

[Fletchette]

You may be interested in some of experimentation done by the likes of Dick Casull on duplex and triplex loads. The idea was to build a load with powders of different burning rates arranged in stages in an effort to fill in the dips in the pressure curve as the bullet traveled down the barrel.

Note: Don't mess with this kind of load if you value your life or limbs.

That is interesting, becasue I was thinking along the lines of increasing the primer power while using a slower burning powder.

Nope, not messing with experimental loads (just a mental excercise). If I were to, I'd use a test barrel remotely fired and a large, concrete barrier.

 

[brickeyee]

Back in the 1980s cartridges with steel heads attached to a brass front were available.
This moved the weakest spot in the cartridge to the primer cup. Most blank around 70,000 PSI. No brass flow problems with the head anymore. .300 Magnum from a .30-06 was advertised. ‘Steel heads’ by O’Conner Rifle Products. You could even purchase extra brass fronts.
Data was supplied with pressures estimates from the old Powley calculator. Some of the data included notations like ‘single shot’.
They would fire one shot, with bolt measurements before and after to check for setback. Ouch!
Some modern rifle actions are capable of digesting these rounds, but the margins in the rifle design (including metallurgy) are trending towards zero here. Any defect in the metal will cause a failure, and it may not be on the first round. Steel is nice stuff, but getting near the yield point is a bad idea. It is only tested on a batch basis (at best) and you may have a gun that is not perfectly ‘average’ for the type of steel used.

Adjusting powder burn characteristics is a safer way to up velocity.
As correctly noted above, the area under the pressure time curve determines velocity…the peak of the curve blows things apart. By making a powder burn rate more uniform (bigger fatter peak) you can get more area without increasing the peak.
This is not a home time thing though. Propellant chemistry and burning rate are dependent composition and physical size/shape. Better powders have allowed for velocity increase in the same (or smaller) powder volume.

If you want to fool around you can probably find a powder for almost any cartridge that will result in a full (or even slightly compressed) case. There may be some uniformity advantages but best accuracy may not be achieved.

Load for needed accuracy. Almost any decent caliber will do the job if the shot placements is correct…and that depends on accuracy.

 

[unspellable]

Stretched 44 Magnum

The stretched 44 Magnum is the 445 SuperMag which I shoot. It illustrates a point. I have a two or three hundred fps edge over the 44 Mag while running exactly the same pressures as the 44 Mag. So why try to overload the 44 Mag? Now the 445 revolver has a longer cylinder and frame, so it weighs more. But you want the increased weight to keep the recoil within reason.

Now a 44 Special case full to compression with Bullseye might reach the same velocity, but a revolver strong enough to contain it will probably weigh as much as the 445 SuperMag revolver. And you would need some sort of special case such as the steel head mentioned above and maybe electronic ignition to get rid of the weak point due to the primer.

 

[1911Tuner]

Word

Dinking around with powder charges and velocities is all part of the handloader's world...and it's a lot of fun as long as one understands the risks involved...and there are many. Reading pressure signs is only an estimation, and isn't to be confused with safe or unsafe ammunition. Generally speaking...by the time you start to notice that the ammo is a bit "hot", you're already well beyond what is reasonable.

A wise man once said of a .308 caliber rifle:

"The pressures required to drive a 150 grain bullet to 2800 fps in 20 inches of barrel is more than enough to blow your eyeballs through the back of your head."

(20 inches being roughly the actual length of rifled tube in a 22 inch barrel)

As a hobbyist ballistician, bear in mind that you don't have access to the equipment necessary to know...not estimate...KNOW...what pressures that you ammunition is hitting in a particular gun. Proceed with all due caution. With standard .45 ACP hardball, you're touching off about 20,000 psi roughly 18 inches from the end of your nose.