We've discussed this ad nauseum before, but here's a few things you're not considering.

First, the brass can also fail, leaking gas out of the action.  Leaking gas is a danger itself, as it can damage the shooter.  It also carries particles of brass or steel or powder with it, which can harm the shooter.  it also can cut the steel, starting a chain of events that can cause other failures.

Second, the springiness of the action you asked about can cause brass failure.  The springiness of the action is caused by the fact that all steel elestically stretches, then stretches non-elastically (yields), then catastrophically fails.  The arrangement of the block, hammer, hammer pins, etc on a rolling block adds several components to the action that have inherent movement to them, and that can stretch or yield even before failing, with the result that the action stretches open slightly.   

The third thing that you arent taking into account is incremental failure, or localized failure.  An analogy to this is tearing a phone book, a stunt that is sometimes done to amaze onlookers with the persons strength.  If you try to tear the phone book all at once, it is un-doable.  However, if you offset the edges slightly, so that you start tearing at the front or back, you can easily rip the book in two, since once it starts to tear, it continues with less effort than if you were to start the tear at full width.

If an action or barrel gets gas cut by escaping gases at high temp/pressure, it can start to "tear" at the cut, and the failure can perpetuate at less than full hoop strength.  A barrel that splits shows this, once the split starts at a thin point, it goes up the barrel through thicker areas.

You are only considering catastrophic failures (blowups) too.  I would consider the action jamming a failure, or bent brass, stretching, bulged primers or bent extractor.  Many of these things could happen with high pressure rounds without blowing up the action.

dave

this gets posted a lot when folks start thinking about too much pressure in a RB

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this posting illustrates what happens on the extreme end when a RB fails.

It seems like you are trying to get someone to agree with you about doing a "here hold my beer and watch this" type experiment, which usually turns out to have bad consequences.

No matter how many times people repeat that these are old actions, designed back in black powder days, there is always someone who wants to push the envelope and take a chance.

When they were chambered in 7mm, the steel was new, the loads were different, etc etc. 

If you need a 7.62 Nato single shot, do it on a Ruger Nbr 1 action.

I thought a roller was a pretty strong action (and they are within their intended purposes) until I saw that all that keeps them from peeling open is the relatively little bit of metal that is the bottom of the threaded area. As a total percentage of overall metal, there really is not much there.

We all know that metal tends to fail at its weakest point. Structurally that is the weakest point. 

Now if you take that action and with a tight fitted barrel, with a hot cartridge, there is going to be metal expansion and metal flexing. If there is radial expansion, the thinnest part of the action, is right there at the bottom of the barrel. Eventually the steel wouldn't return to its original size and then the next time, the barrel would get a running start at it before starting the expansion again.   

Now I do realize and understand that the degree of expansion would have to be measured with precision instruments but it could be measured.

When I was younger, I made parts to repair lots of machinery that failed from metal fatigue, which is a consideration that you have to factor into the calculations and that is a hard thing to quantify, because you don't know the exact metal composition, how many duty cycles that the action has been through, etc. This is what tends to muddy the calculations some. 

On some of the parts at one of the places I worked at, due to the fact they were for the military, elasticity/breakage tests had to be done on the lot of metal the parts were made from. They would randomly chose one of the parts, saw it up to where we could chuck it into a lathe and we would then machine a specificied shape that they would put into a machine and pull it longitudely until it broke. But this was fresh metal.

I think they were a pretty ingenious design for the time frame but they are still a blackpowder design.  A modern action is much more radial through the barrel threads than these old guns (especially a rolling block).

There is a thread that I did a while back that will give you the composition of both the BP RB's and the 1902's.

One thing about the RB's to consider, regarding the springing of the breech blocks is the leverage that the center line of the cartridge has on the pins of the hammer and breech block. No amount of reduction of head space can cure that. While I don't think single firings of new cases will separate the heads, multi firing will. My 1897 in 45/70 at higher pressures (not unsafe pressures) will visibly stretch the heads of new cases so they are ruined after one shot.

Regarding gas escape, the breech block can be bushed so the firing pin can't escape and the BB can be drilled radially in three positions (top and both sides) to intersect with the firing pin for gas escape.

Lastly, DO NOT color case these actions as that is what (my opinion) caused that RB (discribed above) to open up.

Frank

My thoughts about it are just my opinion about looking at the amount of metal there. 

Here is another roller that blew up with black powder

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on a better note, check out this roller

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it is pretty slick