Max pressure vs pressure signs?

J

jonnefudge

New member
Hi,
From what I understand you should not load the marlin 1895 45-70 with higher pressures than 40000 psi. Is it around this limit you start to see pressure signs on the brass? Or could you exceed the limit to dangerous pressures without first getting pressure signs? Is this different with different cartridges?

I am currently loading 51gr Norma 200, 340gr lead cast and LR primer with no pressure signs on the primers. Looks really mild (see pic). However this should not be to far from 400000psi hence the question.

/jonne
 

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Seems like you made a proper load for your rifle to book guidelines.Its working. Be happy.
To "see pressure signs" is not a goal.

Please understand that for the most part,what handloaders call "pressure signs"is in the context of top tier strength modern bolt action rifles,in excess of 60,000 psi. The RIFLE can handle that for a steady diet.
At about this pressure primers and brass MAY give signs to read.(and misinterpret,jump to conclusions,etc)

Often the brass and primers do not give signs of excessive pressure at 40,000
A WLR primer is a WLR primer,in a 243 or a 45-70.

IF you start reading the brass/primer "pressure signs" indicating 65,000 or so PSI,and you are using a 40,000 psi rifle, can you see we have a problem?

Another issue,in some firearms the brass cartridge case is not so well supported .You may be relying on a fair amount of unsupported brass to contain the high pressure gas.

You may not have flattered or extruded primers.Your brass may not have extruded into the bolt face.Nope.Not at 50,000 psi.

But when the side of the case head blows out,the stock splinters,the receiver bulges,and the mag tube blows up,those are "pressure signs"

Or if that single locking lug ,eyeball heat treated on the bolt of a 125 year old Krag feels 50,000 psi,someone may get hurt. But the primers may look
fine.

Bulged revolver cylinders may occur while the primers look "fine"

If you work up a tested book load,even at max,ideally you have no pressure signs.
Velocity in excess of what the manual suggests may be a very important "pressure sign"
Please do not believe an absence of "pressure signs" is a green light to add a bit more powder.
 
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Ok great answer. Just to be clear I was not about to add more powder :)
I am really careful with this stuff but just wondered how it works.
 
Pressure signs on the primers aren't the only sign of excess pressure. You'll have hard extractions and possibly blown out primers as well.
SAAMI spec for the .45-70 is 28,000 PSI, not 40,000. CIP(Europe) says 32,000 PSI.
Where'd your load data come from? Don't have any cast 340 Norma 200 data and neither does Norma's site. Their 300 grain(40 grains difference is too much. And jacketed 350 is not good for a cast bullet. Isn't 51 grains of Norma 200 either.) data runs 29,000 PSI that may be CIP data. Highly unlikely you're anywhere near 28 or 29,000 PSI anyway.
 
HiBC said:
To "see pressure signs" is not a goal.
Click to expand...

The quote above sums it up pretty well.

Once you see pressure signs you are way past the max pressure. It boggles my mind when people tell new reloaders to watch for pressure signs in cartridges like 38 special or 45 ACP. If you're getting pressure signs you are triple the pressure for the cartridge. The best way to avoid over pressure loads is to follow good reloading procedures and stick with published load data that has been cross referenced.
 
Once you see pressure signs you are way past the max pressure.
Click to expand...

Especially when trying to "read" primers. Some primers (federal and winchester) flatten at much lower pressures.

Straight walled cases such as the 45-70 do not produce many warning signs when you near overcharges. I take more stock in comparing chrono data with similar published loads of the powder I'm using. If you must have a reading that can possibly be used to tell you if you are nearing overpressure (for the brass, not the gun) is to measure the case head before and after firing. If it expands .002 (or more than .001) after a single firing, it is likely an over pressured round. As HiBC said, the rifle may handle it just fine all day every day... but the brass may blow out and do all kinds of nasty things.

Even this is not perfect. This will vary from rifle to rifle, chamber to chamber. And to really begin to rely on it, it would be better with a micrometer that measures to .0001 instead of a caliper. By the time a caliper reads .002, the actual size is .0015. That would already be over pressure in some chambers/rifles. It's an imperfect tool, but better than trying to read primers.
 
I don't think the brass is going to show classic bolt gun pressure signs around 40,000 or even at 50,000. It is my opinion the pressure limitation in lever actions will firstly be because the rifle mechanism is overloaded.

I do not hot rod my lever actions, the things are rear locking and even though the modern rifles are made of much better materials than the original 1890 specimens, the things are still very flexible due to the design.

I tested various powders in my 30-30 Win Marlin 336. I lubricated the cases because I wanted as much bolt thrust as I could get, so I could tell if the action was being overloaded. I want sticky extraction when pressures are excessive. My Marlin has a huge chamber and it took several grains over manual maximums to reach "standard" velocities with 170 grain bullets. Which is around 2100 fps in a Marlin 30-30. It is my recollection that the over velocity charges, which I interpret to be over pressure (though the correlation between pressures and velocity is very weak) I began experiencing mechanical abnormalities. I recall that the action was slightly opened after firing. I don't recall extraction difficultly, but it could have been there. I do remember excessive, hard recoil and the lever slightly open. And, accuracy was horrible. These lever actions seemed to be "tuned" to shoot best with standard pressure and velocity loads. Even if you hot load the things, accuracy would be horrible.

Just go out test your loads, compare against factory, if you have a chronograph so much the better because you can compare velocity. If you don't have any mechanical issues, the accuracy acceptable, and you are within load data and velocity data, all should be well.
 
Jonne,

Pressure signs have a lot of variability because neither the brass cases nor the primer cups nor the gun itself are calibrated gauges. Denton Bramwell showed, for example, the same amount of case head expansion in the same gun with the same lot of brass all with the same load history, could show up with as little as 40,000 psi on one case, but show up until 70,000 psi on another (this was a 7.62×54R). So it's that sort of uncertainty range. If you get a sign on one case but not on your others, it may be the case that is too blame.

The Lever gun design has a pressure sign many other guns don't, and that is case growth before resizing. What happens is the sides of the receiver start to stretch, letting the bolt face back up. This happens because the bolt lug engages at the rear of the bolt, where Mauser type actions have their lugs right behind the bolt face. Since a given stress will result in some number of inches stretch per inch of length, the much longer distance to the lug lets more total stretch occur. M.L. McPherson uses this sign with his 1895's. You should check his writing for details, as I'm not comfortable giving the numbers from memory. Just remember that cases normally fill a chamber then get longer when the sizing die tries to squeeze that expanded brass back into a smaller shape. But this is growth in length as-ejected or failure to be able to rechamber the fired case completely.

The tendency of the lever to try to kick open on firing is another one for lever guns in general. They can usually tolerate a little of that, but it shouldn't become too substantial.

I have a collection of other pressure signs here.
 
Yes. I think McPherson has gone up over 50,000, but if 40,000 was a true practical number, then proof would be about at McPherson's level. The gun won't break at proof, but its life expectancy, and especially it accuracy life, will be diminished by shooting too many very hot loads.
 
Lyman thinks 28000 is plenty for .45-70 Marlin, 39000 for Ruger.
But they show .450 Marlin loaded up to 40000. Is the gun different? Is the belted case stronger?

Hodgdon shows loads up to 40000 for .45-70 Marlin and up to 50000 for Ruger.

51 gr of Norma 200 with a 340 cast is pretty much a guessing game.
Maybe Unclenick will Quickload it for you.
 
I do not hot rod my lever actions, the things are rear locking and even though the modern rifles are made of much better materials than the original 1890 specimens, the things are still very flexible due to the design.
Click to expand...
The bolt thrust is going to be very different than a bolt gun, hence he max will be greatly reduced. When I had a 45-70, all I could tolerate was a 405SWC at 1500.
 
Lyman thinks 28000 is plenty for .45-70 Marlin, 39000 for Ruger.
But they show .450 Marlin loaded up to 40000. Is the gun different? Is the belted case stronger?

Hodgdon shows loads up to 40000 for .45-70 Marlin and up to 50000 for Ruger.
Click to expand...

I read an article several years ago stating that the .450 Marlin and the .45-70 1895 Marlin are basically the same action, so I doubt that 40000 would be dangerous in the .45-70 1895. My question, however, is "why load to that pressure level?"

My 1895 in .45-70 becomes just downright painful to shoot at close to maximum "safe" loads. A medium load behind a 405 grain JHP took down a 275 pound Russian boar at around 75 yards and it just dropped in its tracks. My "plinking load" with a 300 grain cast lead at around 1800 fps droped a large white tail deer likewise.

Shooting a .45-70 convinced me that the relatively slow big bullet has more realistic killing power than the lighter, faster small bullets even though the latter may exhibit more kinetic energy. I must admit the deer with the 45-70 was an experiment; I normally use a .243 Win as my deer rifle shooting 100 grain Noser partitions.

The 45-70 is a fun gun to shoot and quite practical at close ranges for any North American game using only the low to medium loads in the handbooks. Until someone successfully clones the North American mastodon, I personally will stick with the more pleasant to shoot low to medium pressure loads in the .45-70 :D
 
I was going to mention that Garrett Cartridges company made its name with .44 Mag and .45-70 loads for dangerous game, the latter peaking at about 35,000 psi (what Garrett calls +P). They now make trapdoor (<18,000 CUP) and standard (28,000 CUP) ammo as well.
 
Shooting a .45-70 convinced me that the relatively slow big bullet has more realistic killing power than the lighter, faster small bullets even though the latter may exhibit more kinetic energy
Click to expand...

They do when the difference is extreme, which is why kinetic energy alone is an imperfect mean of measuring lethality. Its the best single measurement, when a single measurement must be used. But many other factors, including bullet construction, momentum, and even sectional density come into play (sectional density does matter in internal ballistics when talking about penetration)
 
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