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Posted: 7/1/2017 6:03:55 PM EDT
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When given instructions to "expand the case mouth to 0.xxx" (for using a bullet feeder), are they talking about the outside diameter of the case mouth, or the inside diameter? I can see arguments for each, but...
Advice, please. |
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That's funny. I'd say outside diameter simply because it's a lot eaiser for most people to measure.
One thing is sure. There will be approximately .022 to .028 difference in the two measurements so I'd go with outside first and if it doesn't seem like it's enough go inside. Motor BTW: Not at all a silly question. I would have thought that if they are providing a dimension they should specify. That's kinda disappointing. |
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Isn't the answer self-evident from the case type you are using and the dimension quoted?
For the case of 308 Winchester, they might say expand the case mouth to 0.330". That has to be OD, as the bullet is only 0.308. Had they said expand the mouth to 0.306", that has to be ID as the bullet is 0.308 and the case walls are 0.013" each. What a silly question. 
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| This was specifically for pistol bullets. Both RCBS and Hornady recommend expanding the case mouth 0.030 above the bullet diameter (and in each of their printed instructions they have done the math for the user). Since pistol cases tend to be pretty thin, and with 9mm they can be different from one maker to another, it wasn't super obvious which way either one meant. |
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Definitely OD, at least for the Hornady. It did not seem obvious to me either until after I followed the instructions to screw down by 1/2 turn after the case just touches the PTX flare die. For me, the instructions were near to spot on with the required case OD of 0.385" for 9mm.
I tried setting it under that, but form me, because of the indexing, the suggested numbers were needed to avert bullet misalignment to the seating die. They should have specified. |
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Quoted:
This was specifically for pistol bullets. Both RCBS and Hornady recommend expanding the case mouth 0.030 above the bullet diameter (and in each of their printed instructions they have done the math for the user). Since pistol cases tend to be pretty thin, and with 9mm they can be different from one maker to another, it wasn't super obvious which way either one meant. By "expand" you mean to bell the case mouth, as opposed to expanding the neck with an expander ball. In that case, if you are expanding by 0.03", you can use either the ID or the OD. Both will expand about the same amount. The older I get, the fewer of those automation items I use. <-- is that proper english? |
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Quoted:
LOL! Well, why didn't you say so in the first place? By "expand" you mean to bell the case mouth, as opposed to expanding the neck with an expander ball. In that case, if you are expanding by 0.03", you can use either the ID or the OD. Both will expand about the same amount. The older I get, the fewer of those automation items I use. <-- is that proper english? I know what you mean about simplicity versus automation - which often "simplifies" something at the cost of much more complex setup. But I'm looking hard at making my loading time as efficient as possible, which is why I am asking questions now instead of when I run into a problem trying to make things work. I have to say that, despite the tendency of the ARFCOM membership (as a whole) to argue and criticize, this place is a wonderful source of real, practical and well thought out advice on a whole range of subjects. Thanks folks! |
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Quoted:
Looking back, I see that I didn't make it clear I was talking about pistol bullets, and "expand" instead of "flare" or "bell" made the water that much muddier. I know what you mean about simplicity versus automation - which often "simplifies" something at the cost of much more complex setup. But I'm looking hard at making my loading time as efficient as possible, which is why I am asking questions now instead of when I run into a problem trying to make things work. I have to say that, despite the tendency of the ARFCOM membership (as a whole) to argue and criticize, this place is a wonderful source of real, practical and well thought out advice on a whole range of subjects. Thanks folks! I don't load much pistol ammo anymore, not since I stopped shooting IPSC/USPSA. I do understand the desire to load it quickly but, for me, a case or bullet feeder just isn't warrated. A few thousand rounds every now and then, in each cartridge for which I reload, and I am set for a while. Have fun, be safe and enjoy your time! 
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