22LR actual peak/chamber pressures, what are they?

[dellet]

SAAMI max is 24,000. What is real?

Actual operating pressures seem to be a closely guarded secret. Ultimate goal is to have an idea of pressure on the bolt face or on this case falling block.

Any help or references appreciated

 

[Tim s]

Pretty low, most of the match stuff is probably in the 11000-12000 range.

 

[USMCDOC]

I am surprise that you guys didn't just look it up!

http://saami.org/index.cfm

 

[dellet]

SAAMI max is 24,000. That’s a bit higher than soft lead bullets can generally handle.

The rule of thumb formula is BHN X 1422, so a lead bullet would need to have a hardness of 18 or so to be loaded to that pressure. A lot of lead 22 LR bullets are 6- 10 BHN, so that would drop the limit to 8,500-14,000.

The 24,000 limit is generally considered to be what the brass will withstand, and some semi auto actions.

There does not seem to be any info available for what any of the available loads really produce.

The project at hand is a 25 rimfire falling block. 17 WSM cases can be converted. The action at this point becomes the weak link. Since the cartridge was discountinued about 75 years ago, I have not been able to find any info on actual pressures.

Using 22LR pressures, since the action was also chambered in that seems like a reasonable place to start. They just don’t seem to be published any where I can find.

 

[Tim s]

I am surprise that you guys didn't just look it up!

http://saami.org/index.cfm

That's because most 22 ammo is no where near SAAMI max.

 

[Tim s]

SAAMI max is 24,000. That’s a bit higher than soft lead bullets can generally handle.

The rule of thumb formula is BHN X 1422, so a lead bullet would need to have a hardness of 18 or so to be loaded to that pressure. A lot of lead 22 LR bullets are 6- 10 BHN, so that would drop the limit to 8,500-14,000.

The 24,000 limit is generally considered to be what the brass will withstand, and some semi auto actions.

There does not seem to be any info available for what any of the available loads really produce.

The project at hand is a 25 rimfire falling block. 17 WSM cases can be converted. The action at this point becomes the weak link. Since the cartridge was discountinued about 75 years ago, I have not been able to find any info on actual pressures.

Using 22LR pressures, since the action was also chambered in that seems like a reasonable place to start. They just don’t seem to be published any where I can find.

What kind of falling block? Even a low wall in reasonable shape will handle mid size CF chamberings, I would think zero issue in any rimfire chamberings well into the 30's .
You need a followup float this on the ASSRA forum site.

 

[dellet]

What kind of falling block? Even a low wall in reasonable shape will handle mid size CF chamberings, I would think zero issue in any rimfire chamberings well into the 30's .
You need a followup float this on the ASSRA forum site.

One of the rifles is a Stevens favorite, pretty weak action. Basically the block pivot pins take all the stress.

There is actually a discussion over on ASSRA that brought me here. Spent some time going through other threads on some rimfire threads and it appears to be a well kept secret among manufacturers. Found the same question asked many times, many places, no real answers.

If I had to make a guess based on numbers I have seen. They are loaded for pressures based on bullet design and material.

Remember these early rifles were shooting blackpowder for the most part so pressure ranges did not vary so much.

It’s possible to get factory velocities and stay under well under 10,000 so ultimately that’s what will happen. Knowing what actual pressures are would be a very nice piece of the puzzle to have though.

 

[Tim s]

I suspect your last comment is the right approach.
I shoot an English Rook in 297-250 and its about what I do with 60 grain slugs. Got them at about 1050-1100 fps. They will start to extract hard if you're getting close.

 

[dellet]

That and the 255 Jeffery Rook is what I’ve been using for data. The 255 is closer to case capacity.

I also have a 44 1/2 in same chamber. That has done all the load development, more room for error. It also opens up some possibilities for heavier bullets.

 

[Tim s]

corrected above. Computer took over, meant 297-250.

 

[dellet]

This has become a rabbit hole subject for me. The more I look, the more I learn and the more I realize that there is no one correct answer.

For my specific quest, finding a possible safe pressure limit for an older rifle, it will be in the 10,00 psi range.

How I came to that was through a look at bullet hardness.

For the most part 22Lr uses pure lead or something in the 5-6 range of the Brinnel Hardness Number. For a bullet like that to obturate and seal the bore a pressure of 7-8000 psi is needed. Max pressure, when the bullet is overly deformed is around 13,000 psi. Bullet construction and lead hardness will play a role. The heeled bullet behaves a bit different than a flat base.

These numbers are somewhat consistent with Black Powder loads of when the cartridge was designed. Consider that a .45 Colt has a max Pressure of 14,000, and these numbers start to fall into place.

Through a lot of poking around it seems that "regular 22 Lr" use bullets in the 6 BHN range and "Match" bullets, mostly European are in the 8-10 BHN range. In theory meaning they will need to be in the 11-14,000 psi range minimum and possibly being fine approaching the 24,000 max.

As bullet hardness increases, possibly due to plating/washing or for velocity increases, peak pressure will need to increase. Up to possibly the point of case failure. SAAMI minimum proof is 31,000.

An interesting study that I hope is reasonably correct.

Any corrections or additions would be greatly appreciated.

 

[Tim s]

I cannot recall exactly but I believe your Euro match stuff is incorrect, I believe the high end stuff is dead soft, almost pure lead. I shoot a lot of ELEY and Lapua and it's soft.
At the end of the day, and you still worry, why not work up loads, to a velocity spec, using black powder substitutes that won't foul like black ?

 

[dellet]

Good chance a lot of what I have won't pass technical muster since no actual testing was done.

But depending on who the "trusted source" is even a 40/1 lead/tin will measure 7 and 30/1 will measure 8. Some will say those same ratios will be as hard as 9. Those will still be some very soft bullets, considering many commercial cowboy action bullets are sold with a BHN of 12. Of course those are cast, not swaged, so they need the mix to flow better in the molds.

Eky Tenex 00120 pistol

The benefits of this cartridge include a round nose bullet profile to ease feeding in semi-automatic pistols and rifles. The projectile is made from a high specification lead antimony alloy which reduces surface damage when cycled through the firearm.

Being made of an alloy to reduce damage from feeding is a harder bullet. I found a couple of similar descriptions.

Remington match made by Ely

When it comes to competition-grade rimfire ammunition, there’s only one name good enough to share the Remington® brand – Eley. The Target Rifle ammunition is a high quality, general-purpose rifle cartridge that averages a one-inch, 10-shot, 50-meter group and features a graphite-coated antimony lead alloy bullet.

Lead alloy will be harder, how much is anyone's guess

There were also a couple of obscure references to a Military Match round with a 10 BHN and multiple references to home testing with various consumer grade tools producing as much as 12, which probably indicates some operator error.

All this to say my, original question shows I did not know enough about the subject to ask an intelligent question. I could have just as easily asked "what is the peak pressure of a 30 caliber cartridge". There are that many variations of a 22Lr.

Armed with all of this new found knowledge, gained from reverse engineering, I think I can put a few loads together that will meet or exceed original specs, without putting undo stress(350- 500 pounds) on a 100 plus year action. Maybe it will still be usable for a couple more generations.

Basically an academic exercise, but the best I can without real numbers from real sources.

 

[George Steele]

This has become a rabbit hole subject for me. The more I look, the more I learn and the more I realize that there is no one correct answer.

For my specific quest, finding a possible safe pressure limit for an older rifle, it will be in the 10,000 psi range.

How I came to that was through a look at bullet hardness.

For the most part 22Lr uses pure lead or something in the 5-6 range of the Brinnel Hardness Number. For a bullet like that to obturate and seal the bore a pressure of 7-8000 psi is needed. Max pressure, when the bullet is overly deformed is around 13,000 psi. Bullet construction and lead hardness will play a role. The heeled bullet behaves a bit different than a flat base.

These numbers are somewhat consistent with Black Powder loads of when the cartridge was designed. Consider that a .45 Colt has a max Pressure of 14,000, and these numbers start to fall into place.

Through a lot of poking around it seems that "regular 22 Lr" use bullets in the 6 BHN range and "Match" bullets, mostly European are in the 8-10 BHN range. In theory meaning they will need to be in the 11-14,000 psi range minimum and possibly being fine approaching the 24,000 max.

As bullet hardness increases, possibly due to plating/washing or for velocity increases, peak pressure will need to increase. Up to possibly the point of case failure. SAAMI minimum proof is 31,000.

An interesting study that I hope is reasonably correct.

Any corrections or additions would be greatly appreciated.

I have read accounts of experimenters pulling the bullets and powder out of old .22 LR black powder cases (they wouldn't fire - the primer compound was dead) and reloading modern cases with the black powder and original bullets, then firing them and chronographing the results, which came in at about 1,009 f/s. Loading others with modern Swiss Null B, which is finer than 4F, took velocities into the 1,140 range. Since that's in the range of modern .22 LR velocities, I suspect that the pressure is analogous - but the different burn profiles could well mean that effective internal pressure of smokeless rounds is at a lower peak than the old black powder, but sustained for a longer time.

Most pressure curves I've seen for black powder show peak pressure in about 90 - 125 microseconds, vs. smokeless in 150 - 250 microseconds. Perhaps the hotter CCI's take the pressures up into the SAAMI max range in order to achieve their higher velocities. Compared with .22 Magnum, with its higher case capacity, peak pressure would probably mirror that of the CCI hot loads, up near the SAAMI max.

On another note, I've seen reports of people using .22 nail gun blanks and 18-20 grain .22 pellets for pellet guns, getting velocities up into the high 2,500 to near 3,000 f/s range without any indication of overpressure on the cartridge case. Pellets are lighter weight, however; I suspect that using a 40 grain .22 bullet would cause problems with excess pressure, indicating greater than 24,000 psi. Given that the velocities are so high, the normally-experienced pressure must be quite a bit lower, so that speaks to the assumption that pressures are, indeed, in the range you suggest.

 

[dellet]

I have read accounts of experimenters pulling the bullets and powder out of old .22 LR black powder cases (they wouldn't fire - the primer compound was dead) and reloading modern cases with the black powder and original bullets, then firing them and chronographing the results, which came in at about 1,009 f/s. Loading others with modern Swiss Null B, which is finer than 4F, took velocities into the 1,140 range. Since that's in the range of modern .22 LR velocities, I suspect that the pressure is analogous - but the different burn profiles could well mean that effective internal pressure of smokeless rounds is at a lower peak than the old black powder, but sustained for a longer time.

Most pressure curves I've seen for black powder show peak pressure in about 90 - 125 microseconds, vs. smokeless in 150 - 250 microseconds. Perhaps the hotter CCI's take the pressures up into the SAAMI max range in order to achieve their higher velocities. Compared with .22 Magnum, with its higher case capacity, peak pressure would probably mirror that of the CCI hot loads, up near the SAAMI max.

On another note, I've seen reports of people using .22 nail gun blanks and 18-20 grain .22 pellets for pellet guns, getting velocities up into the high 2,500 to near 3,000 f/s range without any indication of overpressure on the cartridge case. Pellets are lighter weight, however; I suspect that using a 40 grain .22 bullet would cause problems with excess pressure, indicating greater than 24,000 psi. Given that the velocities are so high, the normally-experienced pressure must be quite a bit lower, so that speaks to the assumption that pressures are, indeed, in the range you suggest.

One of the work arounds for the .25 rimfire is to breech seat the bullet and use a low powered 27 nail gun blank, which was basically the parent cartridge of the 17WSM.

The same idea is used for some of the other obsolete rimfire. The 32rf uses a 32 long case (or purpose made case) with the base cut out to accept the blank.

The next step was to pull the bullet from the 17 WSM, and recreate the whole cartridge, originals on the left. I use a 60 grain cast instead of the Hornady, although in a modern action with a faster twist, a modern 25 or 243 rimfire could interesting.