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Conflicting 9mm "crimping" info?


quicksilver
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I'm getting different stories from different people as far as how much crimp (taper crimp) there should be on a 9mm load. I have a dillon case gauge the local shop told me to only take off the bell right to the point where the case will fit into the gauge then stop. The problem is when it's at that point, the bullet isn't very secure. It doesn't take much force to push the bullet back into the brass. When I measured the mouth when it just hit the point of making it into the case gauge, it measured .382. when I measure some factory ammo it measured more .376-.379. I hear that making that too tight can cause pressure problems, bullet turning, etc. I just want to make sure I'm doing this safely. What is the right amount of "crimp" to put on it? Is it based on measuring the mouth? Is it how much of a dent you put in the round? I am using Berry's plated 115 gr 9mm bullets for this first batch. Thanks for any clarification!

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I shoot for .376-.378 ish. That pretty much just removes the bell. As for the bullets being able to be pushed into the case, Crimp is not the issue. What cases is this happening with? FC by chance? As a matter of fact some say too much crimp actually loosens neck tension. I use an EGW undersize sizing die and I can not push bullets into the case even if I don't crimp them at all.

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The actual case mouth measurement can differ depending on the brand of brass since they differ in case wall thickness. The better advice is that the taper crimp be about 0.001 - 0.002 inches.

Which typically falls in the .376-.378 range.

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It is much more of a sizing issue. You want the case sized down to where the bullet does not want to easily slide into the case. When you bell the case you are opening up the mouth just enough for the bullet to slide into the case without shaving the bullet at all. The case below the belling should be snug enough that you CANNOT push the bullet in by hand. The mechanical advantage of the press will force the case open as the bullet is slid into place.

Now you apply enough crimp to remove the belling and it should chamber without any problem.

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FC is thin walled. I don't know about S&B because I don't mess with it anymore since finding brass colored STEEL cases mixed in. Also I found the primer pockets a little tight for my liking.

FC walls are thin enough to allow bullet set back with some sizing dies. My dillon die was allowing bullets to push in with ease.

Run a magnet through the S&B brass to make sure it is all brass.

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It is much more of a sizing issue. You want the case sized down to where the bullet does not want to easily slide into the case. When you bell the case you are opening up the mouth just enough for the bullet to slide into the case without shaving the bullet at all. The case below the belling should be snug enough that you CANNOT push the bullet in by hand. The mechanical advantage of the press will force the case open as the bullet is slid into place.

Now you apply enough crimp to remove the belling and it should chamber without any problem.

So it could also be that I need to adjust my sizing die as well then? And also increase the crimp a little as well getting it into the .376-.378 range.

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It is much more of a sizing issue. You want the case sized down to where the bullet does not want to easily slide into the case. When you bell the case you are opening up the mouth just enough for the bullet to slide into the case without shaving the bullet at all. The case below the belling should be snug enough that you CANNOT push the bullet in by hand. The mechanical advantage of the press will force the case open as the bullet is slid into place.

Now you apply enough crimp to remove the belling and it should chamber without any problem.

So it could also be that I need to adjust my sizing die as well then? And also increase the crimp a little as well getting it into the .376-.378 range.

Is your sizing die just kissing the shell plate on the down stroke? If it is there is nothing else to adjust to increase the sizing amount.

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Plated bullets are much more sensitive to the crimping process but the above suggestions are excellent, I have mine about the same, .376 to .378 but never more than .380, for all my bullets. Most 9mm bullets are usually about .355 and the brass wall thickness is right around .020 so add that together and it's .375 but you want a little more for variance hence the recommendations of .376-.378. Make sure you have enough bell with plated (just like lead) since the plating will scratch easily. You can see this if you take one and run it across a piece of course sandpaper a time or two, the lead will be exposed. Jacketed will not ...unless you keep rubbing it for a while :)

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It is much more of a sizing issue. You want the case sized down to where the bullet does not want to easily slide into the case. When you bell the case you are opening up the mouth just enough for the bullet to slide into the case without shaving the bullet at all. The case below the belling should be snug enough that you CANNOT push the bullet in by hand. The mechanical advantage of the press will force the case open as the bullet is slid into place.

Now you apply enough crimp to remove the belling and it should chamber without any problem.

So it could also be that I need to adjust my sizing die as well then? And also increase the crimp a little as well getting it into the .376-.378 range.

Is your sizing die just kissing the shell plate on the down stroke? If it is there is nothing else to adjust to increase the sizing amount.

Yes it is.

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