I hear alot that low pressure will show the same indicators as high pressure at times. I understand this but if you see signs, How do you know which way to go? For instance i had a flattened primer, Flattened casehead lettering, unburned powder (small amount)and residue on the table, Which i'm told can mean high OR low pressures. So how do you know whether to go up a step or down? I took mine down and all signs of pressure went away. I'm just looking for well experienced lads to help me with this.

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hear alot that low pressure will show the same indicators as high pressure at times. I understand this

OK....I don't!

The only low pressure sign that can mimic a high pressure sign, that I am aware of, is the flattened primer. Case head smearing, sticky bolt lift, a true flattened primer, all high pressure signs. I have only seen unburnt powder in a high pressure load w/ too slow a powder used in a short bbl give high pressure signs & leave unburnt powder, but that is more a product of the short bbl.

The way to tell if the pressure is low:

1. Unburned powder in the barrel pretty much always means low.

2. Primer backed out of the primer pocket (i.e., not flattened) usually means low.

3. What does the manual say? If you're at the lower end of recommended loads, then the pressure is probably low.

The way to tell if the pressure is high:

1. Sticky ejection. If ejection is sticky in a clean firearm in good mechanical condition then the pressure is high.

2. Primer flattened clear out to the edges.

3. Loads at the upper end of those recommended in a manual.

4. Blown or pierced primers.

5. Rapidly expanding primer pockets on reloading and/or poor brass life. Defective brass can also cause these signs.

6. Group sizes that have been decreasing as a load is increased and then start to widen again.

7. Cases from a semiauto that have been landing in about the same place and then start to be thrown erratically to markedly different places.

8. Cases from a semiauto on which scuff marks start to appear on the body of ejected cases.

9. Extractor marks swaged into the case head.

I've probably missed some.

You have to know an individual gun as well because different guns and different actions types will show signs of pressure in different sequences.

Now I'm sure you've all heard about light powder charges in large capacity cases using slow powders (it can happen with fast powders as well). The result can be high pressure signs like flattened primers, splintered stocks and sticky ejection as well as hang fires. What happens is that the bullet starts to engage the bore but the pressure isn't quite high enough to push it clear through. The powder is still burning and the pressure keeps rising until it's high enough to push the bullet that was kind of stuck, out of the bore. As we all know, it takes quite a bit less pressure to get a bullet going down the bore with a little jump between the bullet and the lands than to start a bullet that is already engaging the lands. You might think of it as the closest you can get to a squib load (a load with which the bullets remain in the bore) without having a squib load.

So, in the latter case, though the load is light, the pressure is quite high. In other words, case head smearing, sticky bolt lift, very flattened primers are signs of high pressure even if the powder charge is low unless the chamber is dirty or there is some mechanical defect in the firearm.

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I hear alot that low pressure will show the same indicators as high pressure at times.

I feel this statement is wrong. In a 30-30 with a starting load the primer might back out of the case. But even this is not the same as a high pressure signs. If you do research of load data for the bullet your using and use the starting load first and go from there the sign on the brass will let you know. There are times when a starting load in some brass (Prvi Partizan brass 308) will cause high pressure, the signs will be there. High pressure signs are- Primer flattened,no rounded edge or flowing into firing pin hole. Web has expanded. Ejector mark on head. Hard bolt lift. Hard or sticky extraction of the brass out of revolver cylinders. See photos here of pressure signs. photos

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Originally posted by icemanls2:
So how do you know whether to go up a step or down?

If, as every reloading manual will caution beginners, you're working up your recipe from the starting load and everything's fine so far, and then, WAMMO you get signs, like you describe, of high pressure, for goodness sake don't increase the powder charge.

Unless you're NOT following the always reliable, time tested, bullet and gunpowder maker's approved procedure. High pressure signs don't just jump out of nowhere and bite you in the ass unless you're not following acceptable procedures.

Ok, maybe i wasn't clear enough. I was working on a load with unknown 4831. In one of my manuals Starting load for IMR4831 was 55 grains, Starting load for H4831 was 56 grains. I loaded 5 rounds with 56 grains and showed signs of pressure on 1 out of 5, they were all matched weighed loads, all cases trimmed same etc. flat primer to the edge, scuffing on case and casehead lettering smeared.But i also had unburned powder. This was in an autoloader. If i was following a book with known powder i would probably know which way to go, but i wasn't. I backed off a few steps and signs went away so i worked back up until i reached sign again which was 55.5 grains. I'm just trying to learn so i'm asking questions.

what cartridge?

If your primer reseating is really firm, the pressure is low. If the reseating is easier than a new case, then the pressure was high. I am assuming that the lot of brass was not too soft or too old.

In auto loaders head space tolerances are high & so cases stretch and the case head does have a higher back thrust on recoil.

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9. Extractor marks swaged into the case head.

Common occurrence on the Ruger Mini-14. Maybe because it jerks the case out so rapidly and so brutally...

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Originally posted by Ol` Joe:
what cartridge?

30-06, 150 SP, CCI 200

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Originally posted by icemanls2:
...How do you know which way to go? ... So how do you know whether to go up a step or down? ...

Unless you compare the Pressure Ring Expansion(PRE) with what happened in a Factory cartridge, you are only guessing.

Nothing tricky about it, you just need to use the PRE portion of the never-fail, always-reliable, time-tested, relatively-inexpensive CHE & PRE.

And as a major side benefit, you will also know you have not totally wasted $$$HUGE$$$ on a noncalibrated, guessed-at-dimension, Haphazard SGS, as can be laughed at in the historical, non-biased, completely-laughable "GLOATING" thread.

Or, you can keep guessing.

Best of luck to you.

IMO, with a semi-automatic, I think traditional pressure signs are kinda out the window. The "slam bam" cycling of the piece can cause what appears to be pressure signs.
I'm not too familar with semi's but I would think that a reloader would try to acchieve as smooth a cycling of the action as possible rather than looking for high velocity.
I know that if you get too hot with your loads in a semi, things can start to break.

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Originally posted by icemanls2:
I hear alot that low pressure will show the same indicators as high pressure at times. I understand this but if you see signs, How do you know which way to go? For instance i had a flattened primer, Flattened casehead lettering, unburned powder (small amount)and residue on the table, Which i'm told can mean high OR low pressures.

Nobody said that "Flattened casehead lettering" could be a sign of low pressure.

Oh, and a smeared casehead is not the same as "Flattened casehead lettering" either.

"Ejector wipes" AKA "smeared casehead" can be caused by 2 things - over pressure loads OR by too slow of powder causing high gas port pressure causing the action to open before the case releases from the chamber walls.

As I have said, and others too, not only is 4831 rather unsuited for 150gr 30/06 loads, it is really unsuitable for gas guns.

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This was in an autoloader.

You should not use slow powders like UNKNOWN 4831 in some 30-06 auto rifles.Certain makes/models can break an operating rod or something??? Might be an M1 Grand???

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Originally posted by icemanls2:

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Originally posted by Ol` Joe:
what cartridge?

30-06, 150 SP, CCI 200

Way too slow of a powder for this application. I wouldn`t go any slower the one of the 4350s with a 150 gr in the 06. I don`t think one could cram enough H4831 in a 30-06 case with a 150gr bullet to reach std SAAMI max pressures.
The others guess that you are seeing low pressures are right on IMO. Save the 4831 for 180gr and up and try something in the burn rate of 4064-IMR4350 with your bullet.

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Originally posted by BECoole:
Nobody said that "Flattened casehead lettering" could be a sign of low pressure.

Oh, and a smeared casehead is not the same as "Flattened casehead lettering" either.

"Ejector wipes" AKA "smeared casehead" can be caused by 2 things - over pressure loads OR by too slow of powder causing high gas port pressure causing the action to open before the case releases from the chamber walls.

As I have said, and others too, not only is 4831 rather unsuited for 150gr 30/06 loads, it is really unsuitable for gas guns.

This is a good example of some of the complexities of loading for semi autos.

muck

If this is way too slow of a powder for a 30-06 with a 150 grain bullet, and we should use published loads per say, Then why would several manuals take the time to print them useing 150 grain bullets? The only reason i chose 150 is because i have a ton of them and figured i'd try them instead of my good hunting bullets like accubonds.

I appreciate that you are trying to use this powder and are experiencing frustration over it's performance.

But not all published loads are good loads in all or even any rifles. The load you tried might be "good enough" to get rid of some powder in a bolt action. Heck, somebody might even find it to be a very accurate load in their rifle, even if it is somewhat dirty or low velocity. Somebody else may not have any other powder and they just need to whack a deer at 50 yards. All they need to know is that it is an option.

But it depends upon the rifle. I wouldn't shoot just any published load out of a Garand and I wouldn't shoot just any published load out of a Winchester '95 either. Not all published loads would be optimum or even safe in those weapons. You have to know your weapon and it's strengths/weaknesses. Not all rifles in any given caliber are created equal.

Sorry you've had a rough time with this, but thankfully, God loves experimenters and I'm sure you'll see a lot of different pressure signs over your lifetime. Dumping a primer now and again isn't usually the end of the world. Just don't get crazy and try to get rifle velocities with pistol powders or anything like that. Don't get discouraged. A lot of guys here have a lifetime of experience that took a lifetime to acquire. You will get there too. And once in a while you'll have to step into the deep end just like you've done here.

One last thing. You have got to admit that this has been fascinating.

Now go load up some IMR4064 for that 30/06 and save the 4831 for your .270 or whatever you have that has a higher capacity/bore ratio than the '06.

Thanks Becoole, I didn't think i was stepping out there too far but Geez, You'd think i WAS stuffing em with Bullseye or somthing. I was trying to be safe about it and there is only 1 grain difference between tha starting loads of both 4831's. Anyways thanks, If it doesn't work out I have no problem pitching it, But i figured I'd try thats all.I'm gonna try the same load in a bolt gun, I just don't try somthing brand new like that in my good guns till i know it's close.

I think you have done a really good job with it.

You didn't created a hazardous condition, just a sub-optimal load for the weapon. But that's part of experimenting!

The reason not to use too slow a powder in an M1 Garand is that the operating rod can be bent.

The Hornady reloading manual has published loads specifically for the Garand and it would be best to stick with powders no slower than those listed.

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Originally posted by icemanls2:
If this is way too slow of a powder for a 30-06 with a 150 grain bullet, and we should use published loads per say, Then why would several manuals take the time to print them useing 150 grain bullets? The only reason i chose 150 is because i have a ton of them and figured i'd try them instead of my good hunting bullets like accubonds.

It'll work for a 30-06, but it's not a good powder for use in a gas operated autoloader. With a bolt action you'd be all right, but there's another consideration that has to be taken into account for gas operated autoloaders, that's the pressure at the gas port in the barrel. Obviously different powders have different burning characteristics and it's been found that using the slower burning powders like 4831 creates a high pressure situation in the autoloaders gas system. I believe the traditional load for a M1 Garand used IMR 4064, which is quite a bit faster than 4831. I don't know a whole lot about the subject, but I do know that most say to stay away from slow burning powders in autoloaders. I'd save the 4831 for something else and go with a more mid range powder if I were loading for an autoloader.

Iceman,
If you are asking that basic of a question about pressure signs it may be prudent to be extremely cautious when working up loads involving "unknowns", especially for autoloaders. Especially if the autoloader has expensive parts that bend, break or unlock under high psi if subjected to the wrong pressure curve.
Good articles on reloading for semi autos-
http://www.exteriorballistics....ics/gasgunreload.cfm
http://www.zediker.com/downloads/m14.html

I think the new Hornady book has loads just for the M1.