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9mm case belling, how much is enough


Mbauer67

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I am having a little trouble figuring how much to bell the mouth of a 9mm case to maintain proper Bullet alignment. A lot of people say just enough to let the bullet sit on the mouth of the case, but I am having a little trouble figuring out just how much that is.

Is there a way to measure the amount of bell, or picture maybe.

Any advice?

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.380 is the outside diameter of a loaded round in my Lyman manual so for a bell I would suggest something like .004 more than an empty sized case. Your CMJ can get by with less bell than a plated or moly bullet. That said my Dillon is set so I don't scrape the coating on a 130gr BBI.

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The correct answer is impossible since you did not tell us what kind of bullet you are loading, Moly, Cast, Jacketed etc. In general terms some where between .378 and .382. The higher number for Moly coated bullets. Note that mixed brass is mixed brass thickness varies and you have to compromise to get all of them to work properly.

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Interesting. I just installed a Hornady Bullet 9mm seating die and they recommend belling the 9mm case to .385--the bullet does seat perfecting using this amount of belling

I have the early version of the bullet feeder and it says .382 in the manual, but I've run .384-.385 with good results. If it just came with a muffler it would be better.

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I am having a little trouble figuring how much to bell the mouth of a 9mm case to maintain proper Bullet alignment. A lot of people say just enough to let the bullet sit on the mouth of the case, but I am having a little trouble figuring out just how much that is.

Is there a way to measure the amount of bell, or picture maybe.

Any advice?

.015" over the sized mouth size.

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Although you don't want to go too much, this isn't a critical part of reloading that requires measuring. If the bullet balances on the top of the case without holding it, there's enough bell. Within reason, there's a pretty broad range of acceptable amount of bell. Personally, I am happy with just enough bell to barely be able to see the fact that the case is belled, and in my experience, it has worked perfectly.

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