Pressure signs not showing at Max load

Discussion in 'Reloading' started by MOOSE39465, Aug 12, 2019 at 8:03 PM.


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  1. Indian7953

    Indian7953 Active Member

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    I have a 7 mm Rem mag that calls for a max charge of 71 grs. of powder but it shoots 69.7Gr. max, if I go over that it starts showing brass on the bolt face similar to yours. I also have a Winchester 264 magnum that craters all primers no matter what the charge is. It looks to me like you are right there at max load don’t go over it.
     
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  2. Tumbleweed

    Tumbleweed Well-Known Member

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    Primer cratering doesn't necessarily mean Jack. I'll agree with you on the faint little smilie face that's just barely showing up. Chances are that barrel harmonics will be a problem much higher than this anyway
     
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  3. nicholasjohn

    nicholasjohn Well-Known Member

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    I've used the method described in this
    I have been wondering if anybody was doing this any more, and I'm glad you brought it up. This is very much like the old "copper crusher" pressure measuring method that used to be the industry standard. I've been doing this for decades, with a blade micrometer. ( A regular micrometer won't work; the posts will hang up on the rim of the case and the expansion ring on the case wall on the other side. The spot in between that we want to measure - just ahead of the extractor groove - will not be in contact with the faces of the posts of the micrometer.) I also C-clamp the mike to a flat surface, and stand the cartridge case on top of the calibration washer for the tool, so that I will uniformly measure each case at the same height above the head every time. Repeatability is key.

    Employing this method, the blades of the micrometer touch the case walls immediately above the extractor groove, and I do it at a mark I have made on the side of the case with a black magic marker. ( These cases are not always perfectly round, so measuring at the same spot on the circumference is critical to the accuracy of this method.) I write the measurement on the case with the same marker, so that I know what I'm comparing to after I shoot that round.

    I have read Hodgdon's manual on this, as well as an older Hornady manual. Dave Scovill also wrote this up years ago in Handloader Magazine. Others have commented on it, and it was once considered SOP to do this. ( NICK HARVEY'S PRACTICAL RELOADING MANUAL devotes a whole chapter to it. ) The general consensus is that with the 30-06 case head, .0005" of expansion is maximum. I've also found that most factory loads expand around .0003". So, I have determined that .0005" is absolute max, and .0003" has been my "in the field" max or "hunting max." When I load to .0003" of case head expansion, I almost always find velocity to be very close to factory load velocity, and I've never had an issue of any kind at that pressure level. I'm now considering "splitting the difference" and just adopting .0004" as an all-around number to work with, and just let it go at that.

    The whole story here is that these measurements are not telling us actual pressures, but relative pressures. Relative to what ? Relative to what the bullet, powder and ammunition manufacturers have found with their fancy testing equipment using min-spec pressure barrels. That's why I think that going to .0004" expansion is probably not going to cause me any problems in the field. Having road-tested the .0003" value for twenty years, I'm ready to move it up a notch - but not two notches. That last .0001" is my safety buffer.

    Speaking of two notches above factory loads, Scovill's article showed that his .0005" expansion coincided very closely with 60,000 PSI when he measured pressure using both his method with case head expansion concurrently with some bullet company's pressure-testing equipment. Just throwing that out there for you guys to chew on, if you're so inclined.

    Lastly, I'd like to say that I'm a bit surprised that this method has fallen from favor, or at least doesn't get talked about much. It seems to work pretty well, but I must admit that it may a little conservative for most guys, and it is kind of a pain in the keester to do.
     
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  4. Old Blue Dawg

    Old Blue Dawg Member

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    1. Primers mean nothing. 2. Measuring cases heads mean a little. Only a pressure transducer set up tells the truth.

    If you are exceeding the velocity of premium factory ammo with the same bullet & bbl length, you could be pushing your luck. Or you could have a very loose barrel with lotsa freebore.

    Now while I love the 6.5 CM (I own 3), considering it a "Long Range HUNTING cartridge" is wishful thinking. Targets yes, big game no. It can't even equal the 6.5x55 in a modern rifle. I also have 2 6.5x55s and a 6.5x55 AI and a 6.5mm Long Range hunting cartridge, the 6.5-300 BEE. In my 30" bbl. point blank on deer size game is 400 yards +.

    I'm a "get real close" guy when it comes to animals (cept bad hoomins) but love banging steel.

    6.5x55 vs 6.5 BEE and my No. 1 6.5 BEE

    6.5x55 & 6.5-300 Weatherby.jpg


    Ruger No. 1 6.5-300.jpg
     
  5. jmfishin

    jmfishin Member

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  6. crkckr

    crkckr Well-Known Member

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    I'm seeing a lot of "flat" statements that may or may not be true for any given rifle. Yes, there are signs of pressure. No, there are no signs of pressure. Well, hogwash! Bear with me here, it's gonna be a bit of a trip!

    There is only one use for factory ammo in my book, and that's getting a baseline on what your brass is going to look like after firing (plus you get some velocity data to beat!). I have rifles that always crater primers and I have rifles and pistols that always leave marks on the primers, as if the bolt or breech face were dirty. They aren't dirty, it's just the machine marks that get imprinted on the primer.

    Extractor/ejector marks are another thing that a factory round will let you know about. I also have rifles that leave faint marks on the rim of the cartridge, just like in Mooses' picture. If you know for a fact that your rifle does that all the time, then you can be assured it isn't a pressure sign. But you *must* have something to compare to! I have factory (or low to mid range reloads) for each of my rifles and pistols so I have something to compare to. For instance, I have a S&W .357 that craters and flattens primers, even with mid range .38's! So I see flattened primers with all magnum loads, it's just something I expect.

    A cratered primer can be one of several symptoms, from too much pressure (drop your load 2 grains and see if it still craters them. If yes, it's not a reliable pressure sign. If no... yep, you're getting close to max pressure with that primer) to a soft primer, to an oversized firing pin hole. Change primes to a harder brand and see if that helps.

    This reloading stuff is mostly science but it's part voodoo, too! Weird and crazy things just happen at times, with no particular or obvious reason. The reason can usually be figured out (as in, "science the livin' 'ca-ca' out of it")... usually. And what seems logical often isn't!

    Using reloading data from old books is ok for a reference but when it comes to minimum or maximum loads, you're taking your life in your hands, unless you have powder, primers and bullets from that era! Powders change over the years, get less or more bulky or powerful, faster or slower burning... so you should always use data that's the same age as your components.

    There are very few flat statements you can make about reloading, especially when it comes to someone else's firearm & situation. Close, yes. Principles, yes. Theory, yes (a theory is something proven to this date but is subject to change with more information. A hypothesis is someones idea or best guess!) But flat statements can often come back to bite us where it hurts the most!

    Moose, load up just one round with 2 gr. less powder and see if you still get the same signs on your brass (polish it up real nice so you can tell). And/or try a different brand of primer. You might also try loading a round, closing the bolt carefully, then eject the round and check for marks! I think these things alone might tell you lot more than all the conflicting ideas that have been tossed around in the last 7 pages! Someones going to be right and someones going to be close and someone is likely to be flat out wrong. But only you can actually figure it out for sure!
    Cheers,
    crkckr
     
    Last edited: Aug 14, 2019 at 6:38 AM
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  7. 7mmTikkaShooter

    7mmTikkaShooter Member

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    Codyadams nailed it. Don’t go higher. Cratered primer is an early indicator of reaching max pressure but not always super reliable. The ejector mark however, in conjunction with the cratering would tell me it’s getting high and I would not take it any further.
     
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  8. Nowoolies

    Nowoolies Well-Known Member

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    G'day moose
    Mate your getting very close ,you have ejector marks for a start at oo in creedmore and that primer is cratered big time
    Back off two grains and work your load again but keep away from the load your using
    Cheers
    Paul
     
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  9. TwoMore

    TwoMore Well-Known Member LRH Team Member

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    I would measure my primer pocket width. you can buy gauge pins from MSC for about 4 bucks each. I use a .109 and a .1095 once I see a case getting to the .1095 mark quickly my pockets are opening up and I will look for a lower pressure settup. I wildcat a bunch and the pockets are precious to me lol, as on some of my rifles the brass have a ton of work. I agree with cody, I see some pressure
     
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  10. 98dyna

    98dyna Active Member

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    Had to full length resize for first reload because they wouldn't fit in my chamber just neck or bump sizing. My guess is the guy that shot the ammo had a maximum spec chamber and some hot factory ammo (Hornady did have a problem with some 140 Amax rounds when they first started selling it). Second reload was a .002 bump sizing but I think by that time they had already stretched out to far to be saved.
     
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  11. clownbuster

    clownbuster Well-Known Member

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    Then I'd wait on performing any load development until you have about 100 - 150 down the barrel. The barrel will "break in", speed up, and increase in pressure. Just dope the rounds you have and go have fun with it for the next 75 rounds until then.
     
    Last edited: Aug 14, 2019 at 10:43 AM
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  12. nicholasjohn

    nicholasjohn Well-Known Member

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    I think you're onto an important point, Sir. Not all brass is created equal. Years ago, I had an interesting conversation with a guy about this. He was the guy who makes Wipe-Out bore cleaner, and at the time he was also importing Norma cartridge brass. He told me that both Norma and Lapua are what he called "proof-grade" brass, and that commercial brass made here in the US was not. US-made proof grade brass, he said, was not then available for purchase by the shooting public. I have no idea what is going on nowadays in this regard, but I do know that all the available cartridge brass is not of the same hardness and durability. ( Ditto for primers.) So, that is why I prefer the case head measurement process to determine what is a maximum load in my rifle, and only with the brass & bullet that I am using.

    I do think that if velocity is substantially higher than the loads listed in the manuals you can be sure that so are pressures. If that is so, it's up to the individual shooter to decide if he wants to operate in that area of the performance envelope. Out there in the "top-right corner" of the envelope, a lot can go wrong. Knowing how the pressures you're getting is affecting the particular brand of brass you're using is essential. Also, quantifying it is a good idea. Marks on the case head may not be telling you what you think they are, because we don't know how much pressure it takes to generate the back-thrust necessary to make those marks. ( It may take a scary pressure value to put these marks there on some of the harder brass that is on the market, and the shooter may be way too far down the path when he first notices the pressure signs.) It definitely doesn't take the same amount with one manufacturer's brass as it does with a different manufacturer, and that is an important point. I think that is your point, isn't it ?
     
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  13. Old Blue Dawg

    Old Blue Dawg Member

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    "I do think that if velocity is substantially higher than the loads listed in the manuals you can be sure that so are pressures." What I said, what he said. Absent pressure tranducers the rest is just outdated thinking.

    No animal will ever know that the bullet which killed him was going 100 fps faster.

    Pages of opinions mean nothing. If you want to shoot a 6.5 bullet faster than a CM will, buy a 6.5 with a longer bbl and more powder capacity.

    Anyone can understand the a 300 WinMag shoots the same bullet fatser than a 308 Winny !

    This old girl shoot faster than a typical CM because the bbl is 7" longer ! (6.5x55)

    M96 6.5x55.jpg
     
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  14. Don A Parsons

    Don A Parsons Well-Known Member

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    Sometimes folks or even my self want more out of a cartridge that we picked,,, if can be done if we modify the case and select a proven powder / primer / boolit combination,,, but sometimes it might be wizer to pick the next size cartridges that is larger...

    An example might be a 308 Winchester,,, if we need to step it up a bit the idea might be a 30/06 or 300 Mag,,, if we still need more then jump into the larger case magnums or move into the 338 line up...

    Still not enough,,,.move into the 378 magnum or 408...

    Kinda like me on my build,,, I like the idea of the 6.5x47,,, 260,,, the Creed,,, instead of pushing the peak maximum charge I scaled up the cartridge to the 6.5 A-square so I can take it easy on the cases...

    The 140 boolitz can top out at 2900 to 2950 ft-per seconds easy if not a fraction more...

    I have the 147 grain'ers running at 2850 + for speed,, good enough for this Kow girl... Ha

    If we want more,,, go a bit bigger,,, only makes sense to me and others I'm thinking...

    JMO that is

    Cheers
     
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