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Old September 10, 2020, 09:55 AM   #1
Cannonfuse
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Does a .22 short generate higher pressure than a .45 colt?

http://www.lasc.us/SAAMIMaxPressure.htm

According to this tabel a .22 short produce higher pressure (21 000 PSI) than a .45 long colt (14 000 PSI). But why? A .22 short propells a 29 grains bullet with less powder compared to a .45 colt - that propells a 250 grains bullet.
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Old September 10, 2020, 10:10 AM   #2
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Less powder AND a smaller combustion chamber. This is why different cartridges use different powder charges. .357 magnum and .44 magnum operate at similar pressures but use substantially different amounts of powder to achieve the pressure.
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Old September 10, 2020, 10:49 AM   #3
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Standard .45 Colt should be within the pressure ranges for black powder. Remember the cartridge is 150 or so years old and guns designed for that pressure range are still around.

That is why you find reloading information for .45 Colt labeled in different ways for only certain modern firearms like Ruger single actions or Contender. Those loads are roughly equivalent of .44 magnum, a much newer cartridge.
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Old September 10, 2020, 12:09 PM   #4
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Originally Posted by ballardw
Standard .45 Colt should be within the pressure ranges for black powder. Remember the cartridge is 150 or so years old and guns designed for that pressure range are still around.
.22 Short is also a black powder cartridge. In fact. .22 Short was the very first fully self-contained metallic cartridge. When S&W introduced their first revolver with bored-through chambers, it was chambered in .22 Short.

Today, though, some manufacturers are pushing that little 27- or 29-grain bullet to supersonic velocities out of that tiny case.
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Old September 10, 2020, 02:20 PM   #5
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Size doesn't matter.
Burn rate, powder charge, projectile mass, bore friction, bore length, and many other things come into play.

But size does actually matter. The small chamber of .22 Short firearms allows higher pressure to be contained in low quality materials, than a larger chamber, even at lower pressure.

Quote:
.22 Short was the very first fully self-contained metallic cartridge.
If you qualify that with "modern", I can let it slide.

Otherwise, one must assume that needle-fire and pinfire do not qualify as self-contained; even though several of the self-contained Pauly needle cartridges used brass casings (1808-1812), and nearly all pinfire casings were self-contained brass or copper (1830/1835+).
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Old September 10, 2020, 02:38 PM   #6
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But size does actually matter. The small chamber of .22 Short firearms allows higher pressure to be contained in low quality materials, than a larger chamber, even at lower pressure.
I thought the opposite was true. If the same amount of powder and bullet mass are used in a small and a large caliber, the smaller caliber will require more of the barrel material? A magnum rifle cartridge in .22 will generate higher pressure and require better and/or thicker steel than a 12 gauge shotgun?
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Old September 10, 2020, 05:35 PM   #7
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Higher pressure = you need better material and/or more of it.

My example was a representation of "smaller hole = more strength".

If you take the same type of firearm and chamber them for .22 Short and .45 Colt, respectively, the .22 Short can handle higher pressure because there is more material left around the chamber(s). *Assuming all other stressed portions of the firearm can handle the pressure and thrust, as well.
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Old September 10, 2020, 06:52 PM   #8
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Pressure is force/area

Consider the area of the .22 compared to the area of a .45.

A woman wearing stiletto high heels can generate much more pressure on the ground than a big burly lumberjack wearing sneakers.
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Old September 10, 2020, 07:08 PM   #9
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It’s true that .22 barrels and revolver cylinders use to have more steel. Perhaps higher pressure is a reason for this? In a .45 colt revolver chamber the wall thickness use to be very thin, I haven’t measured but approximately about .05”. However, if we take a look at this document https://www.cip-bobp.org/homologatio...s/a-4-1-en.pdf that list steel quality and wall thickness based on different calibers (only shotguns and rifles) it’s stated that a .22 short only need 1.2 millimeter wall thickness. I believe that the main reason that .22 revolver cylinders, pistols and rifles are overdimensioned is because it doesn’t hurt to put some extra steel in them, while in a .45 dimension is more critical.

In the document it’s also stated that small bore shotguns require more steel compared to the big bore, which I believe most people initially will find weird. But these guns are operating at more similar powder charges and shooting projectiles that has more similar weight, I can understand that a smaller bore in those cases will create higher pressure.

But I still find it weird that a small .22 short, with light bullet and light load, generate higher pressure than a heavy bullet and heavy load .45 colt. I’ve shot both cartridges, and the difference regarding recoil and sound is significant.

If we were to make two experiment barrels with the same steel and wall thickness. One chambered in .22 and one chambered in .45, and we gradually turned them down - I wounder which barrel will burst first?
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Old September 10, 2020, 08:04 PM   #10
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Quote:
In fact. .22 Short was the very first fully self-contained metallic cartridge.
As noted above as long as we exclude the needle and pinfires:

That honor goes to the 22 BB Cap (6mm Flobert) 1845

The 22 Short didn't come around to 1857 but it has the distinction of having powder as part of the combination.
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Old September 11, 2020, 03:20 AM   #11
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Quote:
Does a .22 short generate higher pressure than a .45 colt?
Yes - it's a good example of Boyle's Law - which states that pressure and volume are inversely proportional - in other words, as volume goes up - pressures go down.

(which of course - is only the tip of the iceberg as far as what's going on...)
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Old September 11, 2020, 09:57 AM   #12
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CannonFuse: “... I wonder which will burst first”... the burst strength of a pipe follows Barlow’s Formula:
P=2 S t / d

P is the pressure where things either yield or burst, depending on which value of S one uses
S is the yield (deformation) or burst strength of your barrel materiel
t is the thickness of your barrel walls
d is the outside diameter of your barrel.

A little bit of algebra shows

t = P d / (2 S)

Let’s assume same materials, so same strength and let’s assume .45 OD is roughly 2 times .22 outside diameter... for the INside diameter...

So you can play with the algebra where the inside diameter + 2t = outside diameter... and the dog is pestering me and not letting me do math but... basically this will get you thinking about things like “how come shotgun barrels are so thin?” and “how is it you can make an air rifle pellet go 1,000 FPS with just one stout pull on a long lever attached to the rifle?
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Old September 11, 2020, 11:35 AM   #13
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Quote:
Originally Posted by Cannonfuse View Post
But I still find it weird that a small .22 short, with light bullet and light load, generate higher pressure than a heavy bullet and heavy load .45 colt. I’ve shot both cartridges, and the difference regarding recoil and sound is significant.
The .22 has a higher PSI but that's only one variable The .45 Colt creates a lot more energy but it's over a larger area, so even with a lower PSI it still generates more force. You can't view PSI as the sole factor of energy.

You could catch a golf ball going 70 miles per hour bare handed. Try that with a bowling ball going 60 MPH and it'll take your arm off even though the bowling ball is going slower. You can't just compare one variable of an equation.
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Old September 17, 2020, 12:14 PM   #14
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And the 25 acp has a max pressure of 25,000 psi.

While the 38 Spl. works at 17,000 psi and the 38 Special +P operates at 18,500.

The lowly 45 acp at 21,000 psi.

Does this mean the 25 acp outpowers them all?

No.

You and your pals probably figured this out when you were a kid. You just haven't applied those lessons to something else.

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Old October 7, 2020, 04:00 PM   #15
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Quote:
But I still find it weird that a small .22 short, with light bullet and light load, generate higher pressure than a heavy bullet and heavy load .45 colt. I’ve shot both cartridges, and the difference regarding recoil and sound is significant.
Some aspects of this question are simple and some not. All together it's a complex question with a good many facets. A person could look at Robert Rinker's book "Understanding Firearm Ballistics" and get the whole picture and answer.


The 22 lr. operates at max pressures of 24,000 psi
The 9mm has a standard max pressure of 35,000 psi
The 44 Spl at 15,500
The 45 Colt at 14,000
The 357 Sig at 40,000
The 454 casull at 65,000

We can see this below and it's as good a reference as others for what we want to see.

http://www.lasc.us/SAAMIMaxPressure.htm

At first look it has no rhyme or reason. But when we consider the weight/mass of the bullets involved, the amount and type of powder, and the size/diameter of the bores something begins to come into focus.

The U.S. Army uses the 22 lr for training and such and it provides some interesting figures for what it uses. I've highlighted some.

Quote:
Long Rifle:

Long Rifle (Lead Bullet), propellant: 1.7 gr smokeless, bullet: 40 gr, overall length: 0.984 inch.
Long Rifle (Commercial), propellant: 2.1 gr smokeless, bullet: 40 gr, overall length: about 1 inch.
Long Rifle, M24 (Jacketed Bullet), propellant: 2.5 gr smokeless, bullet: 40.5 gr, overall length: 0.995 inch.
The first type specifies standard or target velocity .22 LR while the second is common high velocity commercial ammo. While these soft lead round nose bullet types were suitable for training or target practice, they are not legal for use in a war zone. Since .22 LR air crew survival weapons would probably be used in a war zone and could be used for defense, the M24 round is loaded with a hard lead-antimony alloy core bullet with a gilding metal jacket.[24]
The amount of powder used in the 22 lr. is at it's max with the 2.5 grains used in the M24 round. That is a tiny amount of powder compared to centerfire rounds. It's also a tiny case that is too small for a primer so it's a rimfire. So to get a 40.5 grain bullet out of a, lets say, 20 inch rifle barrel with enough energy to do it's job of killing small game, it takes a lot of pressure. Too much pressure and the thin case will rupture (long before a split barrel by the way).

Most loads in use for the 22 small, long and long rifle do not operate at max pressures but below The CCI stinger operates at pressure closer to the max then lead target rounds. Note the lesser amount of powder used for target practice by the Army.

Another point to take into consideration it that while we have bolt action rifles and revolvers for the 22 short and the (basically extinct) 22 long and 22 lr, only the latter will reliably operate most semi auto pistols, rifles and carbines.

When we use a garden hose we usually place a nozzle on it to artificially decrease the diameter of the hose (the pressure of water in the hose remains the same). This increases the speed with which water flows from the nozzle. This is similar to what happens to get a light weight 40 gr. 22 caliber bullet backed by less than 2 grs of powder out of a 20 inch barrel at 1200 fps. With the small amount of powder involved it needs increased pressure to function as it does.

With the 22 caliber 223 Remington we use a max pressure of 55,000 psi to get the same weight 40 gr. bullet to move at over 3,000 fps. For comparison the 45-70 Government operates at 28,000 psi. The latter is a much more powerful cartridge suitable for big game.

There is more involved in this of course. But with this we can look at the relationship of caliber, bullet weight, amount of powder and type, primer and see a pattern emerge in chamber pressure. There is also logic in the cartridges that began as black powder rounds and those that began as smokeless.

Hope this helps.

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