Overpressure potential of substitute bullets in reloading 9mm

Discussion in 'Handloading and Reloading' started by wst38tx, Dec 12, 2020.

  1. wst38tx

    wst38tx Member

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    I’m concerned with safety issues to reload 9mm Luger. I’m new to the 9mm, but not reloading. Unlike other rounds (like 38Special) the 9mm case has nil excess chamber volume. As we know: 1) Published loading data references powder, bullet (style, brand and weight), and COAL. 2) I’ve read the warnings about seating bullets too deep. Even a few thousandths can be disastrous. 3) I buy generic bullets, Everglades has been my favorite for years (also bought RMR). But then I have to trust that any xxx, gr, style bullet will be close enough in length (bullet OAL) that I won’t get in trouble and win a Ka-Boom due to a different bullet OAL reducing case volume and spiking pressure.

    This may seem picky, but I don’t care lose a hand or fingers, etc. Why not specify seating depth? It would be easy to measure.

    I have some Everglades 115 gr CPRN and noted Speer specs (most don’t) bullet AOL, in this case their 115 gr CPRN OAL is 0.557. The Everglades measures 0.555, so this one increases case volume for the same loaded COAL, so it isn’t an overpressure concern for the same data. But then I also have Everglades 147 FMJ and 124 FMJ.

    My use for the 9mm is strictly paper punching – training for personal defense. Accuracy past 10 yards is not an issue. The usual advice is start low and workup, but in this case, one could go from safe to kaboom in short order. I would appreciate hearing some wisdom from some of you with experience related to this.
     
  2. edwardware

    edwardware Member

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    No.

    You can't buy bullets that don't vary by a few thousandths or more in OAL and base-to-ogive, even premium BTHP rifle bullets. Your run of the mill pistol bullets will have even more variation, and that's perfectly fine because it doesn't matter.

    Seating depth and bullet profile does effect pressure, but it's not nearly as sensitive as you've assumed.

    You should demonstrate this for yourself be testing. Pick a bullet, determine plunk COAL, and workup loads at plunk and plunk minus 0.030. You will find a small difference at most.

    Some does, some doesn't.
     
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  3. Skgreen

    Skgreen Member

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    Plunk 'em to determine your max COAL and then use published data for type/weight/charge etc.
     
  4. kmw1954

    kmw1954 Member

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    Published reloading data always shows a length. That length is what the publisher used to develop that published load. Sometimes that length works, other times it does not. So just remember and keep in mind that when length increases pressure decreases and the opposite, when length decreases Pressure increases so adjustments may need to be made to the min and max powder charge.

    When I post load data I do not generally include lengths because what works for my gun may not work in your gun. You need to find that length for your own gun. If the adjusted length is great enough to adjust charge weight I note that.
     
  5. Blue68f100

    Blue68f100 Member

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    The reason its recommended to start low when working up your loads. Some powders are more sensitive to setback than others. TightGroup is one that does not like compressed loads an is sensitive to case volume. I prefer a more forgiving powder. But this is common with most fast burn high nitro powders.
     
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  6. NMexJim

    NMexJim Member

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    I wouldn't avoid any decent mass-manufactured bullet, especially in these times.

    Understanding upfront that there is really no standard for bullet manufacture will get you off on the right foot. You can buy bullets that won't have a specified COL available (flat nose being the worst IMO) and differences such as shank lengths and profiles can all cause trouble. Using another manufacturer's table might be a mistake (ask me how I know this) due to differences hard to detect with the eye.

    I highly suggest the plunk test at the very least to endue the cartridge fits into the chamber.
     
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  7. wst38tx

    wst38tx Member

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    I'm well aware of load development techniques. "Plunk " test has nothing to do with my point, not about COAL, chamber fit, compressed loads, or set-back, but rather case pressure. If my bullet "X" is longer than the published data bullet "Y" and I load it according to data, I have decreased volume and increased pressure regardless of the particular weapon. So I start low and work up till I see pressure signs? Now I am relying on seeing pressure signs to determine a safe load. By the time I see a flattened primer, I'm already in the danger zone.
     
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  8. wst38tx

    wst38tx Member

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    I see your point, thank you. So what you are saying is there is not enough difference in the various manufactures' bullets for a given wt, type, etc. to influence the pressure in the case if load to the same data? Seems to be the answer I am looking for.
     
  9. WeekendReloader

    WeekendReloader Member

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    I have noticed different seating depths do make a difference. I worked up a load using a cast LEE 120grain TC 9mm bullet. Tried a couple of seating depths with the same ladder of charges, incrementing by 0.1 grain. The short OAL would cycle the slide and the long OAL would not at the lower charge ranges.

    Now, when using a bullet that I have no data for, I will calculate seating depth compared to a known good load for my pistol. It helps as another sanity check to help narrow the ladder range for the first load workups.

    There is a difference caused by case volume and bullet seating depth. Just work your way up with the new bullet and you should be safe.
     
  10. Jim Watson

    Jim Watson Member

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    There is a noticeable difference.
    Accurate is one of the few sources for data on the same weight bullet with the same powder, at brand specific OAL.
    Hornady 9mms come up shorter than other brands because of their truncated cone shape and AA loads are lighter for them.
     
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  11. GeoDudeFlorida

    GeoDudeFlorida Member

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    This question is simpler if you are only loading for one gun. What works in one chamber and slide-spring combo may be damage or jam another.

    Best advice I can give is go slow and keep a load book. Documentation is your friend. If you don’t have a chronograph or access to one I highly recommended getting one. They’re a good tool for working up loads.
     
  12. GeoDudeFlorida

    GeoDudeFlorida Member

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    —-
    This is why I was told by some experienced loaders to avoid Blue Dot in 9mm. It tends to get spiky in small cases with long bullets.
     
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  13. kmw1954

    kmw1954 Member

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    Here is an eye opener for you. Cruise on over to Western Powders website and open the reloading data fire. Then scroll down to the 9mm and pick a powder, or all the powders and compare data for a 115 or 124gr bullet. Then pay attention to how much the charge weight varies between bullets of the same weight. It may open your eyes.
     
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  14. edwardware

    edwardware Member

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    There is a difference; bullet profile, material, and seating depth do drive pressure. . . but it's not so sensitive as to be destructive across small changes.

    @kmw1954 has a good idea, and it's a cheap way to get a feel for how much variation is inherent in the data. Multiple manuals, especially decades apart is another useful tool.

    So, start at start, work up, pay attention. . . but know that there's a lot of variation, and large Safety Factors, built in. If you do this for long you'll eventually find a starting load that shows overpressure signs in your weapon. . . and then you'll be happy you started at start.
     
    Last edited: Dec 12, 2020
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  15. rfwobbly

    rfwobbly Member

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    • Agreed. Everything we do in reloading is to control chamber pressure.
    • If your bullet is significantly longer (your example), OR if your OAL is significantly shorter, then you can make a simple mathematical proportion of the Starting Load as a safety check. That may guide you to lower your Starting Load by 0.1 or 0.2gr. You will not get an exact answer, but you will have a very useful guide. Beginning at the Starting Load, all other "dangers" and notable variations are eliminated by shooting standard incremental loads.
    • The only way to "know for certain" is to use a chrono to measure the bullet's velocity. As you noted, pressure signs for this purpose are nearly worthless. But within the safe loading range, the bullet velocity can accurately indicate safe chamber pressures.

    I think a chrono is in your near future.

    Hope this helps.
     
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  16. Skgreen

    Skgreen Member

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    9mm RMR, Blue, Badman, Brazos, Extreme, Acme, and a few I'm sure I've forgotten along the way,,, loaded 'em by the tens of thousands via plunk, w/o a published COAL and honestly, I have no idea of 'the exact pressure', but no 'kaboom' yet as I avoid min COAL/Max loads and look for problems.

    As always, YMMV
     
    Last edited: Dec 12, 2020
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  17. NMexJim

    NMexJim Member

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    I think Edwardware above has the right answer.

    I went on Everglades website and looked up their 9mm 115 grain FMJ type bullets. They plainly state in their FAQ that they do not offer reloading data, BUT they do recommend that you use your powder supplier's recommendation for a "similar bullet". This is about par for the course with aftermarket bullets.

    FYI, my books say 1.100 Nosler, 1.100 for Sierra, 1.135 for Speer, 1.100 Hornady. Hodgdon says 1.169 and that's the SAAMI max
    COAL.
     
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  18. GeoDudeFlorida

    GeoDudeFlorida Member

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    Something interesting to observe is that the older reloading manuals - I looked specifically at Lyman 44th ed. - do not list COAL for each bullet, just the max and trim length for that cartridge. Back then you measured the chamber of your guns and loaded by what you had, not what the bullet maker said.
    Something to consider if you have the measuring tools.
     
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  19. wst38tx

    wst38tx Member

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    Thanks. Like your comments - spot on. Good advice, but I'm not going to get a chrono. I spent several years building loads for a wildcat, without a chrono, so I know the meticulous fun LOL. Fortunately, I had a friend who had one and we would go shooting together now and then. Now I'm retired and just want to do some paper-punching for fun with a 9. But these days, the cost of bullets, dies and brass give me a break-even versus current ammo prices at about 300 rounds, and I can use primers and powder on hand. So I've dusted off the old Rock Chucker. If I were loading for competitive shooting - the chrono would be at the top of my list!
     
  20. wst38tx

    wst38tx Member

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    My experience has been exactly that, for most calibers you stay within min/max and set bullet depth for outside mechanics (magazines, lands contact, accuracy, etc.) But it seems 9mm Luger has an additional aspect to
    worry about. I've seen the quote "A bullet seated just .020 too deep can raise the chamber pressure to 50,000 psi or more." on several forums. As NMexJim noted above, for the same type of bullet, recommended loading depths vary from 1.1 to 1.169. That skunks the 0.020. Geeze, and I worried about setting wadcutters in 38 special o_O
    OK, so I'm not nuts, this is querky. A chrono is a damn good suggestion for 9mm.
     
  21. 9mmepiphany

    9mmepiphany Moderator Staff Member

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    When I switch bullets, my goal is to try to maintain a constant of the volume in the case.

    What I'll do is measure the bullets and compare their length, than I'll add or subtract the difference to see how I'd have to adjust my OAL to maintain that volume. I did that when I switch between the RMR 124gr RN and their FP bullets. I'm seating the RN to 1.150" and the FP to 1.114
     
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  22. fxvr5

    fxvr5 Member

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    OAL is important, no question about it. Seating the bullet deeper than the published load will, in most circumstances, increase pressure. How much increase will likely depend on which bullet and powder (and weight) you use and which cartridge.

    Below is a graph that Ramshot used to include in their load manual. Pressure increased as the bullet was seated deeper, but not by crazy amounts with the bullet and powder (and weight) they used (Zip).

    upload_2020-12-12_19-29-58.png
     
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  23. buck460XVR

    buck460XVR Member

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    Sounds like you know as much about this as these folks your asking. Case capacity does influence pressure and in small cases like 9mm, small differences in case capacity make big differences in pressure. Sticking with bullets of similar profile helps, seating round nose bullets to HP/FP OALs will definitely change pressure more than seating brand X 115 gr RNs to brand Y's 115 RN seating depth. Besides reading primers, one needs to be familiar with their gun. How does recoil feel? How is POI compare to known safe ammo? How far do empties eject as opposed to known safe ammo? Besides using a Chronograph, unless one has pressure testing equipment or sends their ammo in to be tested, it's just a WAG as far as "safe" pressure. Measuring OAL of the bullet itself compared to a known safe(or published recipe) bullet, will tell you what the difference in case capacity will be when OAL is the same.
     
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  24. wst38tx

    wst38tx Member

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    That chart would mean more if it included the same examples for both a "slow" and a "fast" powder for each. Some of the "fast" burning powders suddenly spike when they hit pressure points. The chart you show has some nice neat straight lines. Might be good for "Zip" but don't count on it for all. Also, ambient temperature can change things. I load one big bore cartridge I loaded with 'LilGun. Nice, except in hot weather, suddenly the primers went flat, my ears were ringing (even with good hearing protection), and a few primers pierced. Great load in the winter.
     
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  25. wst38tx

    wst38tx Member

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    Right on! The challenge is when you can't find published OAL length for the bullet you are substituting. Sure you can "work up" but then you are out of the safety zone of published data. Admittedly it's low risk, but one in a million odds against you ain't bad . . . unless you're the one.
     
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