.32HR Magnum and >.327 in IOF revolver

[uncle1]

can anyone tell me is it safe to fire .32 HR Magnum from IOF MK1 revolvers. or if anyone knows what is the maximum safe pressure IOF revolver cylinder can sustain?

[timmy]

32 S&W Long operates at 15,000 psi. The loaded overall length is 32.5mm

(https://en.wikipedia.org/wiki/.32_S%26W_Long)

32 H&R Magnum operates at 21,000 psi, and is 34.3mm

(https://en.wikipedia.org/wiki/.32_H%26R_Magnum)

Regarding pressure, this would be like a "+P" 32 S&W load.

To keep one from using the 32 H&R Magnum in 32 S&W revolvers, the case is made somewhat longer than 32 S&W revolvers. This is the same way that 357 Magnum is related to 38 Special, and for the same reason. Inside of the revolver cylinder chambers, there is a shoulder where the chamber is constricted from the diameter of the chamber to the diameter of the throat, which is the diameter of the bullet.

(Incidentally, a critical element in the construction of revolvers is that the throat is the same diameter of the bullet. This ensures that the bullet passes straight, not tilted, into the forcing cone at the back of the barrel. This ensures that the bullet is launched straight from the barrel and flies without a wobble.)

So, it may be that the 32 H&R Magnum won't chamber in an IOF cylinder. That is the way the guns are supposed to be made. If the IOF is worn, or if it is not correctly made, one may be able to force a 32 H&R Magnum round into the 32 S&W Long chamber.

Of course, as you can see, the pressure of the 32 H&R Magnum is higher than what the IOF is made to handle. Proofing guns is done with a higher pressure proof load, and the difference between proof load and normal load is what provides a margin of safety. Whether one is able to use the 32 H&R Magnum round in the IOF depends on whether each individual revolver will stand up to the over pressure round. Fatigue is a cumulative thing, so it may work once or any number of times, or it may not, and the gun may fail at any time, as well. One just doesn't know.

For this reason, I think it is unsafe to fire the 32 H&R magnum in an IOF revolver, even if it could be chambered, which I don't know.

A similar situation exists with using 32 Automatic ammo in the IOF revolver, discussed here: viewtopic.php?f=12&t=28002

The 32 Automatic can be loaded in the IOF in this case, but there are other dimensional issues involved that make this practice unsafe, as discussed. But here again, pressure is an issue, as the IOF's safe load limit is exceeded by the 32 Automatic cartridge. If and when this practice might causee a failure of the revolver is unknown, but a definite risk.

Regarding 327 Federal Magnum, the pressure it operates at is 45,000 psi, three times the pressure that the IOF design limit.

(https://en.wikipedia.org/wiki/.327_Federal_Magnum)

I would guess that this pressure is more than enough to blow up an IOF revolver with the first shot. Not only might the cylinder fail, but the top opening lock might fail, as well.

Note that the 327 Federal Magnum is 37 mm long. Not only would it be too long to chamber in a 32 S&W Long chamber, it may extend beyond the front of the cylinder, preventing it from rotating.

[marksman]

The answer is "NO" unless one wants one's fingers and thumb amputated in real hurry.

Marksman

[uncle1]

thanks for ur insight @timmy. I know it is not good to chamber these rounds in the revolver and certainly, I m not going to chamber them moreover, they are not easily available so that's another constraint. What I want to do is theoretically explore the possibility.
I have an engineering background and I know some things about the IOF design language. Usually, they keep FOS (factor of safety) of plus 3, and a friend of mine told me the pressure it can sustain is higher than 60,000psi (which again matches with their design). Thus chambering .32HR magnum is somewhat possible. Though .327 is risky actually too risky. So it was just to know if someone has done this kind of experiment.

[timmy]

thanks for ur insight @timmy. I know it is not good to chamber these rounds in the revolver and certainly, I m not going to chamber them moreover, they are not easily available so that's another constraint. What I want to do is theoretically explore the possibility.
I have an engineering background and I know some things about the IOF design language. Usually, they keep FOS (factor of safety) of plus 3, and a friend of mine told me the pressure it can sustain is higher than 60,000psi (which again matches with their design). Thus chambering .32HR magnum is somewhat possible. Though .327 is risky actually too risky. So it was just to know if someone has done this kind of experiment.

Uncle, in the spirit of exploring theoretical possibilities, my response to your comments:

1. Fatigue is a cumulative property. For instance, if you bend a piece of steel or aluminum, and then bend it back, it may still be strong enough to do the job (whatever that is -- we're being theoretical here). However, if you continually bend it and straighten it in the same place, it gets weaker, and may finally break along the fold. We often see this in everyday life. Fatigue and stress can induce work-hardening and affect the strength of metal.

The practice of proofing a gun usually involves firing a pressure round of a higher pressure than normal service loadings, and if the gun is still in operable condition, it passes the test. You will note that this does not test for the effects of fatigue, i.e., the continuous use of that proof load or any other load in the gun in question.

Theoretically, then, the proof load only tests just one instance of an overpressure round. It does not provide performance data if 2, 20, or 200 loads of a given pressure are tested.

2. Is the nature of the proof load known with respect to powder used or bullet design or composition? Powders are a funny thing: while they may act one way in one load, in another load, the burn rate of the powder may not act in the same way. For instance, in some slow burning powders, one may load a "light" load and find unburned powder residue after firing. Yet, in a "hotter" load of more pressure, little residue of unburned powder is noted. The higher pressure is what some powders need for complete combustion. This is why, when reloading, caution against using light loads with some powders is given: the pressure affects the burn rate.

This can be dangerous because a light load can cause "detonation," a situation where pressure waves cause localized conditions and the powder spontaneously ignites in an uncontrolled burning, creating immediate very high pressures. This can "ring" the chamber or barrel, causing circular depressions or rings. This may happen after one firing, or be a cumulative effect after a number of firings. Or, the detonation may just blow the gun up.

This is all interesting, but what does it have to do with what we're discussing? You quote a specific pressure level, but that is not all that's involved with gun design and the strength of steel. What is also important is the pressure rise, or the rate at which the increase of pressure takes place. A given pressure may be accommodated if the pressure rising to that level is slow, relative to a different powder or load, where the pressure rise is steeper, or more sharp.

The proof load is, in other words, not the final verdict on determining whether a specific overload will work satisfactorily in a given gun. It's not intended to be so. It only indicates that the gun is safe for service within certain parameters, in this case, the continued use of service level loads. It doesn't test for or provide information about what will happen in the case of continuous use of overloads.

We do know that "+P" loads, or overloads that again conform to a standard level over the original specifications for a cartridge, are used in some guns, those loads being available over the counter. However, those loads WILL[ compromise the service life of smaller and less strongly built guns, such as "pocket guns" like small snub-nosed revolvers, and those made with aluminum alloy frames. Such guns don't stand up under constant use. For instance, in some alloy framed revolvers, the manufacturer recommends just 18 +P loads over the life of the revolver -- no more.

Exeeding the service ratings, as you ask about, of the gun is something that is terra incognita and ill supported by facts and data with regard to the IOF revolvers. The break open frame design is not particularly robust in the first place, and it has been shown in service to be more prone to getting out of adjustment when compared to solid frame revolvers. Thus, one might expect that subjecting the gun to overloads on a continuing basis may shorten the life of the gun, or worse.

Another factor beside the failure of the design must be considered, and that is failure to function. There's no telling whether jams that impede the ability to fire follow-up shots may occur when using overloads, which is a possibility. Of course, the only way to address this is repetitive firings. This is what the military does to see whether a weapon will stand up to a particular set of conditions before it accepts a weapon for service.

3. As you have an engineering background, I'm sure that you can appreciate the validity (or lack thereof) of a "friend of mine told me" data point. I don't think any more needs to be said on that point.

4. I do not believe that an IOF revolver would be safe to fire with a 60,000 psi load under any conditions whatsoever! I'd never consent to firing it with such a load. Frankly, I think 60,000 psi would be sufficient to blow an IOF revolver up. Furthermore, I would want to see any design specifications relating to these matters in writing before I could even begin to consider them. Moving from "Usually, they keep FOS (factor of safety) of plus 3" to assuming that an IOF could handle a 60,000 psi load is far more of a leap than I'd be comfortable with, and I note that you seem to feel the same way, as you conclude that "Though .327 is risky actually too risky."

Again, remember, both the 32 H&R and the 327 Federal loads are longer than the 32 S&W, and may not allow the cylinder to rotate.

All of this is just a theoretical discussion, of course.

[ckkalyan]

Good explanation timmy on a theoretical question!

IMHO - it would be wise to use the ammunition specified by the manufacturer. No offense but, I wouldn't trust the IOF too much with their claims of quality control and testing.