.40AET Posted January 30, 2004 Share Posted January 30, 2004 I checked the FAQ's and could not find any information. Not to say that it is not there. I just bought a Lee FCD for .40. I would like to set up the final bullet crimp to a known good diameter. How much crimp is necessary to get good, dependable, ignition? Thanks very much. Kirk Link to comment Share on other sites More sharing options...
Sixgun Posted January 30, 2004 Share Posted January 30, 2004 The easiest way to determine this is to: 1) measure the diameter of the bullets you are using. 2) measure the case wall thickness at 4 spots around the case mouth. Add these 4 measurements together, and divide by 2. 3) add the measurement in step 1 with the measurement in step 2 together. That will give you the diameter that you need. Hope that helps. Ray C. Link to comment Share on other sites More sharing options...
David Olhasso Posted January 30, 2004 Share Posted January 30, 2004 My method is not too scientific. First I use an undersize sizing die (LEE undersize or Redding) which insures that the case wall holds the bullet and NOT the crimp. With the FCD I insure that the bell from the powder die is removed. I then adjust the FCD till I remove the "squareness" off the brass lips. Essentially, all I am doing is crimping the brass enough to avoid any feeding problems. Link to comment Share on other sites More sharing options...
TBF Posted January 30, 2004 Share Posted January 30, 2004 Bullet dia. + 2x brass thickness - .001 or .002. Works for me. Travis F. Link to comment Share on other sites More sharing options...
warpspeed Posted January 30, 2004 Share Posted January 30, 2004 I remember reading BE one time saying the crimp die for an autoloading pistol cartridge is not a crimp, but a remvoing of the bell created by the powder drop. Bullet diameter + 2 time wall thickness of brass is usually 0.420" depending on brass. I adjust the crimp die down until the case is strait again and I cannot feel the lip at the top. Link to comment Share on other sites More sharing options...
ErikW Posted January 30, 2004 Share Posted January 30, 2004 Somewhere around .422" but the better method is to keep cranking down the crimp die a little bit until the mouth flare is gone and the round passes the case gauge. Link to comment Share on other sites More sharing options...
Rufus The Bum Posted January 30, 2004 Share Posted January 30, 2004 I use .418 exclusively and it works fine. Link to comment Share on other sites More sharing options...
ChuckS Posted January 31, 2004 Share Posted January 31, 2004 The word from Brian: Brian on Crimping Link to comment Share on other sites More sharing options...
warpspeed Posted January 31, 2004 Share Posted January 31, 2004 Rufus, That sound tight. If you pulled the bullert, what does look like ? Link to comment Share on other sites More sharing options...
2cats Posted January 31, 2004 Share Posted January 31, 2004 I'm totally down with "crimp" = bell removal; no more. However, I just got some Starline 9mm to help trouble shoot the set back problem I described in another thread. It looks considerably thicker than either my used Federal or Winchester - around 0.012 - 0.013". If we simply apply the bullet diameter plus twice the thickness of the brass, we get 0.3555" + 0.012" + 0.013" = 0.3805", more than the SAAMI max. So I've got to assume in some cases, like this one (no pun intended), that we have to add the "- 0.001 to 0.002" or "-0.002 to 0.004" parts to this equation, which gets us down around 0.377". Link to comment Share on other sites More sharing options...
TDean Posted January 31, 2004 Share Posted January 31, 2004 .418" here also. But make sure you're measuring at the extreme edge of the case (not .010 from the edge). Link to comment Share on other sites More sharing options...
Rufus The Bum Posted February 1, 2004 Share Posted February 1, 2004 Rufus, That sound tight. If you pulled the bullert, what does look like ? I have never had to pull any bullets, .418 is what Benny Hill recommended to me long ago and that is just what I have went with. It might be a bit more than needed, but I like a good, solid crimp. With .418 I have never seen ANY signs of pressure or drop in accuracy. I think factory is somewhere around .418-.421 Link to comment Share on other sites More sharing options...
kevin c Posted February 1, 2004 Share Posted February 1, 2004 Rufus, That sound tight. If you pulled the bullert, what does look like ? I'm with WS here, at least for jacketed bullets. I've heard that if you pull a loaded round and you see that the case mouth leaves a ring on the bullet, the crimp is too tight, and may alter accuracy by compressing and then separating the jacket from the bullet core. Link to comment Share on other sites More sharing options...
Rufus The Bum Posted February 1, 2004 Share Posted February 1, 2004 Rufus, That sound tight. If you pulled the bullert, what does look like ? I'm with WS here, at least for jacketed bullets. I've heard that if you pull a loaded round and you see that the case mouth leaves a ring on the bullet, the crimp is too tight, and may alter accuracy by compressing and then separating the jacket from the bullet core. I'm not saying a .418 crimp is the ideal crimp, but in my gun with a .418 crimp I get sub 1" groups at 20 yards, so I have not lost any accuracy OR seen any signs of pressure. By all means use a "looser" crimp if you feel the need, there probably is no difference that I can see, but I'm not a fizzicyst, just a redneck Link to comment Share on other sites More sharing options...
.40AET Posted February 1, 2004 Author Share Posted February 1, 2004 Thanks for all of the information. I appreciate everyones advice. Kirk Link to comment Share on other sites More sharing options...
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