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Discussion Starter #1
Just got done rebuilding a 366 for the first time. everything is working well except for the crimp. The first crimp station is good and the 2nd puts on a crimp that I would consider finished. The third crimp is causing the center of the shell to raise up. Should I just eliminate the 3rd station
 

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Try backing off the last crimp die. Station 8. It only needs to take any ‘mushrooming’ out of the shell crimp. Do you have the Hornady manual for the 366?- see page 14. If the shells look good and chamber your gun after station 7, you could go very light on station 8.
 

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What recipe are you using? Hull, wad, powder, and weight of shot?
You may have more in the hull than comfortably fits, and simply backing off on the final taper may just delay the inevitable bulging of the crimp.
On the other hand, the final taper at station 8 shouldn't do much, just kiss the hull before exiting the loader.
 

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And a pic would help. Also, a pic of the part of the die at st. 7 that sits above the die head, so we can see how it is adjusted. But I agree with Slowpoke, lets see the recipe first, it could be a hull stack height problem as opposed to a die adjustment problem.
 

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Discussion Starter #5
Winchester AA comp from Lyman handbook
1 oz 8 shot
Win 209
Fed 12SO wad
18.5 gr American Select
I've also taken the shells apart to make sure I'm getting the right amount of powder and shot
 

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You might find the AASL wad (or claybuster clones) more forgiving for a 1oz payload if your crimps tend to open up over time.
I'm not familiar with American Select powder. I see it is more dense than Red Dot but fluffier than WST, which is what I use in CF AA hulls.
 

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To amplify Slowpoke's reply, the Fed 12S0 wad is made for Federal hulls, which have a difference interior construction than the Win AACF, Win AAHS and all the Rem target hulls. The Fed hulls are "straight-walled," meaning the inside diameter is the same from the top of the hull the the basewad. The other hulls are tapered walled meaning the inside diameter gradually narrows the further down you go. As you might imagine, the over-powder cups of the wads for the two types of hulls have difference outside diameters. The wads for Fed hulls have a bit larger diameter than the ones for the tapered-walled hulls. So, it might be the wad you are using, with its lager diameter, may not be making it all the way down the inside of the hull, causing the wad ram and the crimp die to collapse the crush section, putting upward pressure on the shot cup, causing your tented crimps. Get some either AA-style or Rem Fig.-style wads, they should work better.
 

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Thanks Where do you find info on powder density
Powder density can be inferred from the powder bushing charts. Take two different powders and look for the bushings that drop 18 gr. of each. The one that requires the larger bushing is fluffier than the one the requires the smaller bushing, which will be the denser of the 2.
 

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Discussion Starter #10
To amplify Slowpoke's reply, the Fed 12S0 wad is made for Federal hulls, which have a difference interior construction than the Win AACF, Win AAHS and all the Rem target hulls. The Fed hulls are "straight-walled," meaning the inside diameter is the same from the top of the hull the the basewad. The other hulls are tapered walled meaning the inside diameter gradually narrows the further down you go. As you might imagine, the over-powder cups of the wads for the two types of hulls have difference outside diameters. The wads for Fed hulls have a bit larger diameter than the ones for the tapered-walled hulls. So, it might be the wad you are using, with its lager diameter, may not be making it all the way down the inside of the hull, causing the wad ram and the crimp die to collapse the crush section, putting upward pressure on the shot cup, causing your tented crimps. Get some either AA-style or Rem Fig.-style wads, they should work better.
Thanks Nebs will do.
 

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I find the Lee VMD charts illuminating. Not all powders are listed, but many are. Large number are fluffy, small numbers are dense.
https://leeprecision.com/files/instruct/VMD.pdf
You can calculate a 366 bushing diameter if you embrace the concept of the VMD values.
Of course, the calculated results are not any better than the Bushing Charts.
 

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Discussion Starter #12
Thanks Nebs will do.
I tried the AA12SL wads and they seemed to work better. I also backed off the crimp a little bit. The change in wads takes the pressure down to 7100. I thought you said once you like pressures around 10,000. Will the lower pressure be a problem
 

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I tried the AA12SL wads and they seemed to work better. I also backed off the crimp a little bit. The change in wads takes the pressure down to 7100. I thought you said once you like pressures around 10,000. Will the lower pressure be a problem
That's right, I do like pressures at or above 10k psi. American Select is not a powder that will do that at 1 oz. It's burn rate is too slow. If your load is at 7100 psi, it will be dirty and inconsistent. My practice is to look for loads using faster burning powders because they both produce higher pressures and typically use a tad lighter powder charge. Choosing good recipes is a combination of art and science. You have to get the stack height right to get good crimps. Getting stack height right is a function of hull type, powder density and height of the wad's crush section. Then, there is the issue of pressure, which is a function of powder burn rate. There are several scales that slide here.

PS: It's too bad the online powder guides don't have menus that allow you to select pressure and velocity. It would sure help people narrow things down and probably would not be that much of a programming challenge as the data already is in the database.
 
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