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Thread: Difference in pressure signs in one lot

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    Member Yukoner's Avatar
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    Default Difference in pressure signs in one lot

    I've been working up a load for my .280R, started with 50grains RL-19 (160gr NA), and worked up to 53 grains. Of 8 rounds fired (53gr), about half showed very slight flattening of the primers, with the associated rim on the cup when I de-primed.
    What would account for this difference between the same loads?
    I was very fastidious when it came to measuring my powder, so I am confident that I was as accurate as could be with a standard scale.
    Also, I am not yet using a chronograph, as I am more concerned with whats shooting well out of my rifle, and have no pressure signs. Is not using the chrony handicapping me in terms of not having the complete picture?
    Thanks gents.
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    Quote Originally Posted by Yukoner View Post
    I've been working up a load for my .280R, started with 50grains RL-19 (160gr NA), and worked up to 53 grains. Of 8 rounds fired (53gr), about half showed very slight flattening of the primers, with the associated rim on the cup when I de-primed.
    What would account for this difference between the same loads?
    ....Is not using the chrony handicapping me in terms of not having the complete picture?
    Thanks gents.
    There are numerous possibilities. Among them is the fact that pressure varies from one cartridge to the next, even with precisely the same components. Therefore ammo is loaded to max average pressure without exceeding absolute maximum for an individual round. That is to say that a given load that shows an occasional overload likely exceeds max average pressure even though some rounds are under pressure specifications and appear normal. I'd say that backing off a full grain from 53.0 grains of RL 19 would be a wise practice for now.

    Shooting without a chronograph is not unlike shooting in the dark. I never attempt load development without one because you are simply guessing about velocity and making assumptions concerning pressure. Knowing the facts concerning your handloads is always preferable to guessing about them and a chronograph provides more facts.
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    I agree with 1Cor15:19:

    It's better to rely on velocity than pressure signs alone.

    This is not to say, that a chrono is necessary. It's desirable because you don't have to be quite so restrained. Sooner or later a chrono, will probably show you the shortcomings of pressure signs.

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    Thanks fellows.
    Would loading longer than standard COAL drive pressures up or down with the same weight of bullet and powder?
    After posting this, I went through all my spent factory load brass, and strangely (or not) I found signs, especially in my 7mmRM brass, of slight flattening of the primer in excess of what I observed in my .280 brass of yesterday. Perhaps I am not reading it correctly. I should post a picture and see what you gents thinks.
    Thanks again for the shared knowledge!
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    Primer condition can often be a good indicator of high presssure signs, but not always. Other indicator to check are bolt lift and ejector marks if you are shooting a push feed. No easy answers on this issue as sometimes I even notice cratering on primers when using low pressure loads.
    Try weighing your cases that indicate primer flattening and see if they weigh less. Might indicate less capacity and therefore higher pressures.
    But a more accurate guide might be to see how many times you can reload this brass before the primer pocket works loose.

    Great question, and lots of possible answers!
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    The primers vary in thickness of the cup.
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    One possibility is case trim length. If some are over long they can crimp into the bullet on chambering and significantly raise pressure. If you got this covered ignore the tip.

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    I have had this happen in my 06 when I first started loading. I now suspect the main reason I noticed was I was being very careful and studying each piece of brass real hard for pressure signs, because I was so new to loading. One case normal and the next showing mild pressure signs; sometimes a very little ejector mark, sometimes a slightly flatter primer, sometimes both. I weighted the brass and found that even though it varied a bit in weight, the heavy brass did not nessitarally show the pressure signs and some of the lighter brass did, so I do not think case volume was the cause. All cases well under max length. Since I was not sure what was happening I loaded up some more rounds with 1/2 grain more powder, all showed the slight pressure signs. This was with federal brass which I have been told is less uniform then say Winchester with which I have never had this happen.

    I suspect what was happening was due to variations in the hardness of the brass and primer and variations in pressure. Suppose all the pressures right at the point that pressure signs should start to show are the same but some primers are slightly thinner or softer then the others and some brass is (even thought the same weight) is slightly harder then the others. So the slightly thinner or softer primers will show the pressure and others will not, slightly softer brass will show an ejector mark but the harder will not.

    Of coarse it is really not that simple as the pressures are not all the same. So when I slightly higher pressure round has a harder or thicker primer and slightly harder brass, we see no pressure signs. But a slightly softer brass or primer may show up.

    I now simply see these occasional very mild high pressure signs to mean that I am getting close to a load that I will see pressure on all cases. I have even rarely seen them show up 2 grains below when all cases show pressure signs. I have since come to just see these occasional signs to mean I am getting close and not of signs of a problem yet.

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    Quote Originally Posted by Yukoner View Post
    Thanks fellows.
    Would loading longer than standard COAL drive pressures up or down with the same weight of bullet and powder?
    Generally speaking.

    It would probably result in decreased pressure because, there would be more case capacity for the powder. (If you take a given load and seat the bullets deeper you will increase pressures.)

    If you increased the COAL to where bullet actually touches the lands in the barrel, that will increase pressure, maybe 8,000 psi.

    However pressure varies from round to round, anyway, for various reasons.

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    I'll throw this onto the list of possibilities because a friend drove us nuts with the same kinds of symptoms. It wasn't till we got back to the really basics in his techniques that the "irregular pressure signs" went away: He wasn't cleaning the lube of his cases consistently, so they varied in the way they were grabbing the chamber walls. We cleaned his chamber real good, then used a rag with a little solvent on it to clean the loaded rounds.

    Not saying it's so with yours, but I'd scrub the chamber good and clean the loaded rounds well as a test.

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    Quote Originally Posted by BrownBear View Post
    I'll throw this onto the list of possibilities because a friend drove us nuts with the same kinds of symptoms. It wasn't till we got back to the really basics in his techniques that the "irregular pressure signs" went away: He wasn't cleaning the lube of his cases consistently, so they varied in the way they were grabbing the chamber walls. We cleaned his chamber real good, then used a rag with a little solvent on it to clean the loaded rounds.

    Not saying it's so with yours, but I'd scrub the chamber good and clean the loaded rounds well as a test.
    Nother good idea, I theenk.

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    Default No reality in that statement

    Quote Originally Posted by Smitty of the North View Post
    Generally speaking.

    It would probably result in decreased pressure because, there would be more case capacity for the powder. (If you take a given load and seat the bullets deeper you will increase pressures.)

    If you increased the COAL to where bullet actually touches the lands in the barrel, that will increase pressure, maybe 8,000 psi.

    However pressure varies from round to round, anyway, for various reasons.

    Smitty of the North

    Telling someone that seating a bullet to touch the lands will only increase the pressure 8K PSI has no basis in reality. Are you saying that a Microgroove rifled barrel has the same starting resistance as a deep cut rifled barrel. How about worn V new rifling. A long tapered V flat nose bullet. Fast V slow powder. Reduced load V max Load. Even a Mag V standard primer. There are too many variances to make a blanket statement like that. That kind of a statement, not based on fact or actual data for a specific barrel-bullet-powder combination, could cause someone a lot of problems.

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    Quote Originally Posted by carysguns View Post
    Telling someone that seating a bullet to touch the lands will only increase the pressure 8K PSI has no basis in reality. Are you saying that a Microgroove rifled barrel has the same starting resistance as a deep cut rifled barrel. How about worn V new rifling. A long tapered V flat nose bullet. Fast V slow powder. Reduced load V max Load. Even a Mag V standard primer. There are too many variances to make a blanket statement like that. That kind of a statement, not based on fact or actual data for a specific barrel-bullet-powder combination, could cause someone a lot of problems.
    Whoah. Slow down buddy.
    I think Smitty's "Generally speaking " intro pretty much says it all. Its up to the reader to take the generality and figure it out for his or her own particular firearm.
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    Quote Originally Posted by carysguns View Post
    Telling someone that seating a bullet to touch the lands will only increase the pressure 8K PSI has no basis in reality. Are you saying that a Microgroove rifled barrel has the same starting resistance as a deep cut rifled barrel. How about worn V new rifling. A long tapered V flat nose bullet. Fast V slow powder. Reduced load V max Load. Even a Mag V standard primer. There are too many variances to make a blanket statement like that. That kind of a statement, not based on fact or actual data for a specific barrel-bullet-powder combination, could cause someone a lot of problems.
    Yeah, it's a "general statement". I dunno what your definition of "Blanket Statement" is.

    The figure came from the Quickload ballistics program, that I used for awhile. You were sposed to ADD 8,000 psi to the pressure estimates, if you were seating on the lands.

    Lots of people DO seat ON the lands, and in some applications it results in greater accuracy.

    The effects of some changes in how we load a cartridge, are greater than others. Some may even be negligible. It's good to know which ones are of some consequence.

    As to seating a bullet on the lands, according to the program, it could be as much as 8,000 psi. (That's why I said "maybe 8,000 psi.)

    Actually, knowing this could keep knowledgeable hand loaders OUT of trouble, rather than get them INTO trouble.

    I hafta keep looking this up every time I post it to get it right, but the Lyman Manual #47 says......

    "Keep in mind that in a Ten Shot test there could possibly be as much as a 10,000 psi difference between the highest and lowest pressure generated. This alone, can cause a noticeable difference in the physical condition of the fired case."

    I hope that clears things up for ya.

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    Default The problem with "Generally Speaking"

    Generally speaking:

    Not everyone reading this thread is on the same page in the reloading world. So when something as critical as the idea of touching the lands when reloading is advanced with the "general idea" that "touches the lands in the barrel, that will increase pressure, maybe 8,000 psi" without the proper context or prior knowledge to interpret that statement could cause someone with less than the necessary skills, to have a problem with excess pressure.

    Yes there are a lot of target shooters that touch the lands when they reload. They also invest in the proper tools to measure their chamber with the specific bullet they are going to use. They also "generally" use a reduced powder charge to allow for the increased pressure among other things. I personally seat my bullets 0.040" away from the lands to avoid that variable in chamber pressure because I know about the potential problems when touching the lands with a bullet. 40 thousands of an inch is not a magic number, it just works for me. I have made the investment in tools and taken the time to gather the knowledge to use those tools correctly. I don't expect everyone who reloads to do the same. I do expect them to know the limitations of their cartridge(s) and gather the necessary knowledge to correctly keep themselves and others around them safe. I also know that I can't give some of my loaded 35 Whelen cartridges to other people to shoot in their guns due to the fact that the chamber on that rifle has a lot of free bore so the bullets are seated out farther than would be a safe pressure in a normal or short chambered rifle. One of the truths of reloading is that unless one makes a very generic, by the book, reload one shares reloaded cartridges with some risk.

    All persons who engage in reloading should know the dangers of excessive pressures and what can cause high pressure to happen in what appears to be a safe loading. When one takes on the responsibility of instructing others you have to insure that the knowledge passed on is not only correct for the person being instructed but also for any other person that might read the given information out of context. Tough job.

    From your statement from Lyman Manual #47, given the idea that a max load in cartridge X runs 55K PSI, and that the pressure can vary 5k PSI plus or minus using 55K as the average then the pressure can run from 50k to 60k PSI. In a different post you stated that touching the lands might cause the pressure to rise 8K PSI. So without the context of both posts a load that might have gone from 55k to 63k PSI now has a variable of 58k to 68k PSI. At some point the pressure will be no problem for some firearms to critical for a specific firearm.

    A blanket statement (A blanket statement is a vague and noncommittal statement asserting a premise without providing evidence) and a "general statement" are essentially the same thing.

    "Actually, knowing this could keep knowledgeable hand loaders OUT of trouble, rather than get them INTO trouble." I agree that a knowledgeable hand loader should know this information. It is the un-knowledgeable hand loaders that I worry about.

    I may be a pompous ass. I just may be an ass. I might even be correct. Most of the time I let thing slide that I think are not totally correct. Everyone has their opinion. If I don't agree it doesn't make another opinion wrong, it only comes from a different perspective I may not agree with. Sometimes I feel the need to point out my point of view.

    I hope that clears things up for ya.

    Cary

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    Quote Originally Posted by Yukoner View Post
    Whoah. Slow down buddy.
    I think Smitty's "Generally speaking " intro pretty much says it all. Its up to the reader to take the generality and figure it out for his or her own particular firearm.
    Not to kick over your thread the problem is that some of the potential readers will take the generality, without the knowledge or skill needed to figure it out, and make it gospel. That is the problem. Generally one could say all firearms have the potential to to make a loud noise. After that it gets a little more complicated. Not everyone has the skills to figure it out.

    Nice boat.

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    Okay, we've had your philosophy lecture. Now let's hear you address the original question. That's a problem on the internet, too.

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    carysguns:
    The point is, that when the bullet touches the lands, it can increase the pressure significantly, "maybe 8,000 psi".

    I usually seat .030 OFF the lands, and I don't need to invest in a lot of tools, to do that.

    I agree that.....

    "All persons who engage in reloading should know the dangers of excessive pressures and what can cause high pressure to happen in what appears to be a safe loading."

    It was to that end, that I gave the "Tip". IMO, it wasn't misleading. It was simply a warning. Something to be aware of, and consider.

    I dunno what the Lyman Manual folks were attributing the pressure variations to, but I doubt if they were talkin about seating on the lands.

    Maybe, they were referring to handloading in general. They are probably aware of differences in componets, and some sloppy practices.

    I don't mind those who disagree, or have a different point of view, or that they state it.

    You're welcome to your own perspective on handloading, and the definition of yourself. And, I'm kinda inclined to agree on that one.

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    Yukoner,

    Is this all new brass of the same manufacturer?

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    I could very well be wrong BUT I would say that you have reached the Maximum pressure for your rifle AND that particular set of components. That doesn't elimanate checking for things like over length cases, case capacity etc.

    Two of the things to keep in mind is that the primers might be a little thinner than average for that lot number or they might be just a very small amount softer than average for the lot number. the makers are making thousands an hour and a certain amount of variation has to be allowed in the system or they wouldn't be able to put out a product that any of us could afford.

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