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Thread: Reload Newbie

  1. #51
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    Every rifle will obviously be a little different on how hot a load is in relation to pressure.
    Likely fine with the load mentioned.
    What velocities are you seeing?
    I use a lighted box sometimes called a coffen. It give more reliable reading from a standard chrony in most weather situations.
    Hope your enjoying your reloading experience.

  2. #52
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    Quote Originally Posted by Millsworks View Post
    Every rifle will obviously be a little different on how hot a load is in relation to pressure...
    Kind of untrue depending on how you define your statement.

    The max pressure that a rifle experiences is mostly based upon the powder used, how the bullet is seated, and the internal volume that the cartridge is in. Assuming that we are comparing the same caliber, all rifles will experience slight pressure variations due, partially, to slight variations in the finished chamber and bore, but those variations will be slight and of no great consequence unless the chamber is grossly out of spec. For reloaders the most common factor that creates the greatest amount of excess pressure is either the powder selection and amount and/or the case preparation.

    Steel is steel, when a rifle is made the engineers choose a metal that is rated at a specific tensile strength and if that strength is exceeded, and depending upon the type of metal, then the material will either immediately fracture or simply stretch. Even if it stretches, over time it will crack if put under those extreme pressures time and again. Part of what SAAMI specs do is create a universal standard for engineers to use when they design a rifle. If SAAMI specifies that a certain caliber must be able to withstand at least one round at 75,000 PSI (a proof test value) then the engineers will design the rifle with steel that can withstand pressures that high at least one time. A slight pressure increase above SAAMI specs, say a couple hundred PSI, wont matter much but the closer our pressure gets to the proof test value the quicker the metal will fail. In this case we are talking about somewhere around 10,000 PSI above SAAMI recommendations, that's getting close to their proof test value and that means that the metal will fail far faster than if the pressure were at the standard values. If the life a barrel is something on the order of 100,000 rounds then an over pressure of at least 50% would mean that the the life would be substantially reduced and may be something like 20,000 rounds (arbitrary values but they get the idea across) the reduction in life is exponential so as you apply each over-pressure the life of the metal is shortened faster. It's just like when we bend a piece of metal to break it off. It's very hard to bend it the first time but each time we bend it it gets easier and easier until, in the end, it fractures and breaks off.

  3. #53
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    Some manufacturers Chambers will have a longer or shorter throat, number of rifling lands and grooves, bore diameters for caliber, etc.
    That's what I'm getting at.
    A hot load in a Winchester rifle may be well under max. pressure in a weatherby, all else being the same.
    I have loads that perfome fine in my Remington 700 that's chambered in 7mm mag, but are extra hot on pressure in the mossburg Patriot rifle.
    If loading over recommended max with a rifle a person must use caution. But I have found that the actual max. can be 8-9 grains or more above in some cases.
    Though, in general the manufacturer numbers from the powder companies are usually pretty close.
    I recently found the max shown for Reloader 17 powder in a .338 win mag to be way lwer than I expected.

    Not, that I advacate max loading, but if your experimenting, then you don't know how far it is to you get there.
    Max loads will obviously shorten brass life. But will lessen projectory in some calibers a good deal. Not likely going to find best accuracy with go faster loading. But many times it's exceptable for hunting game bigger than a squirrel.
    In many instances the max loads are just wasted powder though. Faster isn't always better or even good.
    At least in my opinion.
    Max loads can be found by safely moving up the scale slowly and checking for pressure as you go.

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    Nothing is impossible but I suspect that if you are seeing such a huge difference in your 7mm mag ammo then one of those rifles is way out of spec on the chamber dimensions. Quite often you'll find that the chamber has a throat issue when the pressures are higher than expected, either that or you aren't trimming the cases to the proper length.

    I have a bolt action 30-06 that has the same problem, it produces higher pressures from any book load, so much higher that I always have to make my loads a grain of more lower than the book's recommendation in order to get the predicted velocities.

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    Quote Originally Posted by rammont View Post
    Nothing is impossible but I suspect that if you are seeing such a huge difference in your 7mm mag ammo then one of those rifles is way out of spec on the chamber dimensions.
    Not in every case. I have 2 military 03 Springfields, one has minimum headspace, the other maximum. If I reload using the cases fired from the max headspace rifle and neck size them, the bolt will not close on the min headspace rifle with this case. There are a lot of variables, tolerances and differences involved. This is another good reason not exceed maximum recommended loads when reloading.
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  6. #56
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    Quote Originally Posted by rammont View Post
    Nothing is impossible but I suspect that if you are seeing such a huge difference in your 7mm mag ammo then one of those rifles is way out of spec on the chamber dimensions. Quite often you'll find that the chamber has a throat issue when the pressures are higher than expected, either that or you aren't trimming the cases to the proper length.

    I have a bolt action 30-06 that has the same problem, it produces higher pressures from any book load, so much higher that I always have to make my loads a grain of more lower than the book's recommendation in order to get the predicted velocities.
    A one grain difference isn't usually enough to make much difference in my experience. But if your pushing the limits for pressure then I guess one grain could be one to many in some cases.
    I'm one of those Reloader freaks that must have consistency at all stages of my loading. So I trim each and every loading with the Lee trimmer system.
    I also have had many others give me a pet load of theirs , only to find that it won't even cycle in my rifle or allow the bolt to close. Even though the same cartridge worked flawlessly in their rifle.
    In my experience manufacture processing will very enough from one company to another to sometimes creat enough of a difference to be just that. Different.
    Not always a sighn of an actual problem. Guns are designed to operate with factory ammunition of standard specifications.
    Any deviation that doesn't effect function with factory ammo is acceptable in most manufacture standards.
    I have seen this many many instances.
    That's why fired brass that has not been full length resized will sometimes not fit in the chamber of a different make of rifle.

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    Like all of these kinds of discussions, you need to differentiate between the headspace of the cartridge vs. the headspace of the chamber. True headspace is exactly that, the space between the head of the cartridge and the bolt face but for ease of measurement we typically talk about the distance between a datum point on the cartridge and it's head. Headspace errors in the chamber, assuming that the cartridge's headspace is correct, will normally not cause problems with over-pressure, they usually either cause the bolt to not close or you'll find too much case stretch going on and maybe get case head fractures. But lead and throat are areas that can produce a major change in pressure. If the lead doesn't have the correct angle or the throat is too short then the mouth of the case can be compressed in to the shank of the bullet and create high pressures. One grain of powder variation under normal circumstances won't make much difference but, as I've already mentioned, if the throat or lead isn't setup properly then you can see a huge increase in pressure with just one grain difference.

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    Quote Originally Posted by Millsworks View Post
    That's why fired brass that has not been full length resized will sometimes not fit in the chamber of a different make of rifle.
    And sometimes not even in the rifle that it was originally fired in.

    I just went though 100 rounds that I had just reloaded with all the cases having been fired in the same rifle and full length resized and I found 2 that won't chamber and 1 that is a little tight.

    This is one reason that I'll chamber every single reload that I plan on taking into the field to hunt with. It might save you the aggravation of not getting a shot at that trophy animal.
    If you don't care where you are, you are not lost....

  9. #59
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    I 100% agree that the throat is the area that will control how a rifle handles pressure. A manufacturer may use a reamer a little longer than the should have to chamber a few hundred too many barrels.
    Not common, but things happen and it doesn't always cause trouble of any measurable amount.
    Load spec max is info that helps keep us all out of the danger zone. But it is a guide that can't always be spot on in all rifles.
    Caution should be used when coming near a listed max loading for any given powder and bullet combination.
    Safety factors are built into our modern firearms that will keep most sane loaders OK if we push a little too far. But best to not push our luck just because we think we can.

    Load em up and have some fun out there.
    Ammo is more enjoyable when it's fired and fired often.
    Last edited by Millsworks; 12-01-2017 at 09:44 PM.

 

 
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