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Pressure or Force which is more important?

Many times we see firearms originally designed for black powder cartridges used for modern cartridges. The last one was a Ballard chambered in 22-3000. Normally the discussion on the subject gets no further than what the pressure was for the original design and what the pressure is of the modern cartridge. We do need to know the pressure of the cartridge but only to figure the reward force on the rifles bolt, breechblock or whatever. Please keep in mind that I am not considering the gas handling in the rifle or other important things that should be considered. The point of this is too show that there is a lot more involved than what the pressure of the cartridge is.


To figure the reward force

Area of a circle in square inches x pressure (if you have 25,000 PSI and the cartridge has 1 square-inch of surface area the reword force would be 25,000 lbs.) I use the outside base diameter, not the rim, to figure area. To do this properly I think the inside diameter at the base would be used. I don’t know for sure that a 45-70 is 25k or a 22-Hornet is 50K I just pulled some figures out of the air for this post.


Pi Radius-squared
Pi= 3.14
3.14 x Radius x Radius

45-70 at 25,000 PSI
Base diameter .500” so the Radius which is half of the diameter is .250”
3.14 x .250 x .250 x 25,000 = 4907 LBS.

.22-Hornet at 50,000 PSI
Base diameter .294” so the Radius which is half of the diameter is .147”
3.14 x .147 x .147 x 50,000= 3393 LBS

What this shows is that a cartridge with double the pressure can have less force on the action because of the cartridge size. This is the same reason why many double barrel shotguns can be converted safely to double rifles.

Please check my math, I once figured that a 275lb man (me) could hold one pound of gas pressure in a 24” vertical pipe by sitting on a piece of plexiglass while taking a picture of a obstruction in the pipe. I was wrong!

There is, indeed, more to this subject than first meets the eye. Many, many variables, some of them enumerated below:

Rearward force is computed using the ID of the case at the base of the powder chamber plus a variable that's dependent upon the angle & rate of departure of the case wall from the chamber floor, a variable so small that it's not really a factor in this discussion

Rearward force is also dependent upon the deformation resistance of the brass case at the head, that is, a case with thin walls like a Hornet will offer less resistance to stretching than a case with thicker or harder walls at the base

The body taper of the case is sometimes a major factor in the actual force applied to the breech face; owners of S&W M53 22 Jet revolvers or standard 219 Zipper rifles can attest to the fact that certain maximum body tapers tend to grip the chamber walls far more effectively than their minimum-taper brethren, which seems counterintuitive but is nonetheless true

The duration of the force is also a factor in the theoretical yield point of the action; a slap of Bullseye is more likely to damage an older rifle than a shove of black powder under many circumstances

These are only a few of the factors worth consideration.
Regards, Joe

I agree with Joe. It's not always how much force, but more so how fast that force builds up. I always compare it to pushing gradually up vs. slamming into the breech face. Even with equal pressures most guns will take the slower buildup of equal pressure, vs. the quick hit.

So, bottom line. Is a tight Ballard action ok to hold something in the sub-.222 class? R2 Lovell for example, or .218 Bee.

Maybe for a while, then likely it will get loose. Note the case of the Stevens 44, these were made for black powder cartridges up to .38-55 but when revived in the 1930s as the 417 Stevens in .22 Hornet, notwithstanding the smaller head size, they couldn't hold it for long and the calibre was discontinued.

But if there is anyone out there who has a Ballard hot varminter that has had thousands of rounds through it let me hear a different opinon.

What was meant by this?

Michael: I will try an get some pic's posted, it may take a little while. The Ballard action has all the high pressure modification and locks up like a bank vault.

Richard

The high pressure mod's are a small firing pin and the breech block reinforced with a dovetail cut across the face to prevent gas from entering the split block. The action is very tight with no play at all.
pres

I've heard of several Ballards (in calibers I wouldn't chamber for) that are doing fine. I'd rather not test their strength, as I'm afraid of ruining a nice old Ballard myself.

Did the gas pressure force out the obstruction? Any damage to the plexiglas? How thick and what grade plexiglas was involved? Considering plexiglas over bullet proof glass to security reasons on a sliding patio door. Use a steel bar in the track to defeat a "pry-open" against the jamb, and the bearing studs are now metal faced- but hate to install the "bolt in" safety metal bars, due to need for "fire exit" just in case. Present double glass with air pocket "Anderson design"is wired for breakage with sensors into the ADT system, BUT- safety first. By the way, was the top section of the 24" long pipe capped, so that all the gas pressure went downward? How was that configured?? Thanks- And 275 lbs. Arnold Schwarzeneggar?? I'm 6ft 2" solid 217 Ex-Army, but what NFL team did you play for, if I might ask?? That's a "load"!!

It’s been a couple of days and I’m surprised at so little feedback on this subject. The force math seemed to have held up but now we are told this is a bad idea because of the hammering of smokeless powder verses the shoving of black powder. I do not agree with this and don’t understand the reasoning behind it.