22 CB Chamber Presure

[map55b]

Can any one direct me to a reference for the chamber pressure of the 22 CB? Thanks!

[243winxb]

https://saami.org No cb. 22 short is 21,000 psi.

[map55b]

Thank you 243winxb. I was able to find the information on the short too. I'm seeking the allusive 22 Conical Ball Cap or 22 CB. I can not assume that the CB is the same as the short.

[tazman]

https://www.rimfirecentral.com/forum...d.php?t=740233
At the very bottom of post #3 you will find a person quoting that the CB pressure was 18000psi and the short was 21000psi. He also states that you can't find any documentation to support the CB pressure on the internet.
https://thefiringline.com/forums/sho...d.php?t=456943
On this page in post number six is a quote from a CCI employee, while not giving actual pressure, may give usable information.
"The CCI CB shorts do not actually run anywhere near the SAAMI maximum of 21,000 psi. None of our CCI short products 'exceed' that number on average pressure."

[map55b]

Thank you tazman! I am contemplating bringing an antique rifle back to life. I believe the rifle was chambered for 22 CB caps originally which according to these numbers would have a rearward thrust of ~720 lbs compare to a modern 22 LR which is about 960 lbs. While that a 33% increase the delta is still only 240 lbs. Even if I assume that the rifle is made of hot rolled steel it can still support ~45k PSI, so I don't need much material to deal with that delta. I think I will give this project a go and fire it from a "ransom" rest with high velocity 22 LR to "proof" it and look for case deformation.

[Texas by God]

Are you talking about the little pointy headed copper case .22 with an acorn headstamp?

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[map55b]

Greetings TBG: Not sure about the head stamp, but yes: https://en.wikipedia.org/wiki/.22_CB I'm talkin' 6mm Flobert!

[Texas by God]

That's the one I have on my bench. Sorry that I don't have the answer but I can't imagine the pressure being much.

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[map55b]

Thank you TBG I need to get a few projects off the bench before I tackle this next one.

[uscra112]

Working into it backwards using Quickload, pressure to launch a 30 grain bullet at 800 fps. from a 18" barrel calculates to just short of 4000 psi. Those CB caps are probably less. I'm just guessing at the weight of the bullet and the muzzle velocity they may yield. The Aguila Colibri primer-only 20-grain-bulleted round gets about 400 fps if memory serves, and that only needs about 1500 psi.

Mind you, these are only approximations.

The guy from CCI is dead right. No .22 ammunition made today is loaded anywhere near the SAAMI maximum. CCI's Standard Velocity is about 10,000 psi, and High Velocity about 14,000 psi. The infamous Stingers are the only loads that get close - I calculate a little short of 21,000 for those.

If you can provide me better info on bullet weight and muzzle velocity I can calculate bolt thrust for them. I've been down this road already, rehabbing old "boys' rifles".

[map55b]

Thank you uscra112. This helps!

I do not know the velocity of the CBs or BBs for that matter. You hit the nail on the head though, I plan to rehab some boys rifles from the late 1800s. I've been taking the approach from the direction of metallurgy. I "assume" they are made of cast iron (which they are not) with a tensile strength of ~20K PSI, knowing that the material they used is probably closer to hot rolled which is about ~60k PSI. If I assume cast then I have a 3x safety factor. The next factor is design.

I have one each of these:




There is plenty of material in the hammer to contain the SAAMI stated pressure and the hammer spring is very heavy. This is similar to an auto loader firing from an open breach, except I don't want the one in the bottom of the picture to become an auto cocker. Once I've made the worn or missing parts, I'll clamp it to a rest and "proof it" with high velocity 22 LR. I doubt the back thrust will be enough to counter the inertia from the falling hammer. Again max back thrust is ~960lb and probably a lot less, which isn't very much.

[uscra112]

Ah, yes, the ubiquitous Floberts. Got one myself.

The vast majority of cheap guns in that era had frames of malleable iron. White iron castings were packed into airtight boxes surrounded with a oxidizing material, and soaked for many hours in a furnace at low orange heat. The oxygen in the matrix extracts carbon from the iron, leaving behind a metal rather like unto a very low carbon steel. Soft, malleable, and far less brittle than the cast iron that came from the moulds. An amazing variety of cheap household goods were of malleable, including even kitchen scissors, which were cast, annealed, machined, and then case-hardened. Iron pipe fittings that you buy at the hardware store are still malleable iron.

The oxidizer was most commonly "mill scale", which is essentially rust that formed on the surface of steel as was being rolled or forged. 19th century recycling!

Here are some numbers from my bolt-thrust spreadsheet. These are only estimates, being based on the Quickload pressure calculations, which might be off by 10-15%
# thrust
399 - .22 LR Standard Velocity
532 - .22 LR High Velocity
139 - .22 LR CCI Quiet
599 - .22 LR Stinger

[map55b]

uscra112,

Do you mind sharing the chamber pressures you used to calculate your back thrust? If I do the math backwards, I come up with ~15K PSI for the LR Stinger. Thanks! -map

[uscra112]

Thrust psi
399 10500 .22 LR Standard Velocity
532 14000 .22 LR High Velocity
139 03665 .22 LR CCI Quiet
599 15745 .22 LR Stinger