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Thread: Acceptable projectile weight range for load data?

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    Acceptable projectile weight range for load data?

    Is there an acceptable safe guideline regarding how many grains plus or minus in bullet weights you can range from for a given set of load data and feel comfortable you are not risking any safety issues?

    So for example:
    If I have load data for a 100gr Barnes TTSX projectile, could I potentially use that same load data to use a different monolithic copper projectile in 105gr or 95gr? What about 85gr/110gr? What would be the safe range of bullet weights if any (assuming I would be using the lowest published powder charge and building up a safe load, NOT just taking an existing recipe and substituting a new projectile)?

    I see that load data from Hornady, Nosler, and Sierra, for example will often lists multiple projectile types and weights with the same load data for a set of powders. As long as the projectiles are relatively similar, can this concept be safely applied to some of the more custom projectile that donít generally publish specific load data?
    Last edited by ViperTwoSix; 10-09-21 at 11:08. Reason: Clarifying question in title

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    Monolithic Copper projectiles are, if anything, more sensitive to pressure spikes at top of load data than conventional “cup and core” bullets.
    Variations in bullet design with the Monolithic bullet; number of grooves, amount of bearing surface, are in part responsible.
    I would be hesitant to use different bullet weights interchangeably with a given powder charge- certainly at the top of given load data.
    A true "Gun Guy" (or gal) should have familiarity and a modicum of proficiency with most all firearms platforms.

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    Quote Originally Posted by gaijin View Post
    I would be hesitant to use different bullet weights interchangeably with a given powder charge- certainly at the top of given load data.
    Agreed... I think a grain or two or three doesn't matter (say 167gr vs. 168 in .308, or 180s or 182s in .40), but beyond that I would look for proper data.

    If you must DIY your own starting loads, then I might reduce/increase powder charges in keeping with the change in bullet weight, i.e., if you go from 100gr to 110, then reduce the powder by 10%.

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    Quote Originally Posted by ViperTwoSix View Post
    Is there an acceptable safe guideline regarding how many grains plus or minus in bullet weights you can range from for a given set of load data and feel comfortable you are not risking any safety issues?

    So for example:
    If I have load data for a 100gr Barnes TTSX projectile, could I potentially use that same load data to use a different monolithic copper projectile in 105gr or 95gr? What about 85gr/110gr? What would be the safe range of bullet weights if any (assuming I would be using the lowest published powder charge and building up a safe load, NOT just taking an existing recipe and substituting a new projectile)?

    I see that load data from Hornady, Nosler, and Sierra, for example will often lists multiple projectile types and weights with the same load data for a set of powders. As long as the projectiles are relatively similar, can this concept be safely applied to some of the more custom projectile that don’t generally publish specific load data?
    You are generally always safe using heavier bullet load data for a lighter bullet. However, it doesn't work that way using a lighter bullets load data for a heavier bullet. I like to use the difference in % of the bullet weight to determine a starting load when using a lighter bullets load data for a heavier one for which you have no data. But if the differences are only a grain or three, I don't see a problem. If you start low and work up carefully.....

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    Quote Originally Posted by ViperTwoSix View Post
    Is there an acceptable safe guideline regarding how many grains plus or minus in bullet weights you can range from for a given set of load data and feel comfortable you are not risking any safety issues?

    So for example:
    If I have load data for a 100gr Barnes TTSX projectile, could I potentially use that same load data to use a different monolithic copper projectile in 105gr or 95gr? What about 85gr/110gr? What would be the safe range of bullet weights if any (assuming I would be using the lowest published powder charge and building up a safe load, NOT just taking an existing recipe and substituting a new projectile)?

    I see that load data from Hornady, Nosler, and Sierra, for example will often lists multiple projectile types and weights with the same load data for a set of powders. As long as the projectiles are relatively similar, can this concept be safely applied to some of the more custom projectile that donít generally publish specific load data?
    You are generally always safe using heavier bullet load data for a lighter bullet. However, it doesn't work that way using a lighter bullets load data for a heavier bullet. I like to use the difference in % of the bullet weight to determine a starting load when using a lighter bullets load data for a heavier one for which you have no data. But if the differences are only a grain or three, I don't see a problem. If you start low and work up carefully.....

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    Thank you Gaijin, Bimmer, and Bob for the info. Much appreciated!

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    Part of the problem is the issue isn't about the bullet weight. Its about the bearing length of the bullet (how much contact it has with the barrel). Although bullet weight has a large impact on this, so does the bullet shape. Usually the higher the BC using boattails, lengthened ogives etc. the shorter the bearing surface which reduces friction on the barrel. This is offset by the higher weight increasing pressure due to higher inertia. Changing material to solid copper adds more complications.
    This is why it is recommended to back off and work back up to max pressures when changing any component, even just bullets from different brands of the same weight.
    Are there "rules of thumb", sure. It was mentioned its usually safe to use data from a heavier bullet to a lighter one, that's because the powder charge from a heavier bullet max load is only a light/medium load on the lighter bullet.
    I used to shoot/load for a TC Contender, maybe 20 different cartridges. My local TC dealer kept a barrel on the wall of an overloaded barrel. the back 6"s were peeled like a banana. He said it had stuck in the ground like a dart downrange.
    Follow the rules, avoid the temptation to take shortcuts.

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    I'll sub load data for closest possible weight. But there's definitely variances in data for similar weights but different bullet shapes. Like gajin mentioned the bearing surface can change pressure levels a bit.

    Powder lot variances have shocked me too in recent years. I don't like to waste time starting too conservatively on the other hand. Common sense and a little cushion for safety go a long way.
    "You people have too much time on your hands." - scottryan

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    Thanks Hi-wayman and Markm! I appreciate the replies!

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    No problem. I'll look closely at my first few cases after firing if I have any doubt. Checking for swipes... and of course the chronograph is very valuable in piecing the whole picture together.
    "You people have too much time on your hands." - scottryan

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