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Posted: 1/11/2011 10:45:26 AM EDT
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What is the difference in the crimp that a Lee FCD does and the crimp that my RCBS die does (either w/or without seating)?
Why is one better? I do know the theory behind seating and crimpping in two different steps. I'm just not sure, or sold, on why the Lee FCD is a better way to go for getting the crimp. Thanks |
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I think the FCD is a collet type crimp (collet collapses on the neck material radially and applies little or no axial pressure to the case during the crimp operation). The RCBS type of "roll crimp", built in to some of their pistol and most of their rifle caliber seating dies, cams over the lip or mouth of the neck into a smaller diameter. The roll crimp operation applies a definite axial load to the case during the operation. Also, by tucking the edge of the case mouth under a bit, it can slightly reduce the trim length of the case after completion. Some rimless pistol cartridges use the blunt edge of the case mouth to set head space, so tucking it under is not a good thing to do.
The collet crimp will leave a distinct pattern on the case neck similar to this: 
Another advantage of the collet crimp is that it can be used on smooth bullet bodies without cannelures to tighten the neck tension a bit. Roll crimps are not recommended by RCBS on jacketed bullets that do not have a cannelure. |
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Quoted:
What is the difference in the crimp that a Lee FCD does and the crimp that my RCBS die does (either w/or without seating)? Depends on Pistol or Rifle. Lee makes different crimp dies for each. Rifle is a collet crimp and pistol is usually a taper crimp with the added feature of a carbide post sizing ring. Which were you referring to, Rifle or Pistol? |
| I am fairly new to reloading... maybe 2000 .223 reloads so far. I have been impressed with the factory crimp die for several reasons. If you do found range brass, some of it can be less than perfect with dings in the neck. The FCD evens out the roundness of the neck around the bullet when the sizing die might not have been perfect at that job. It helps prevent the bullet from moving in semi auto/magazine feeding... and it increases accuracy, at least it did for me. I think the key is not to crimp too much... it only takes a small amount. I certainly overdid it on my first few rounds, but once i backed off it seemed to work as advertised. Im pleased and plan to continue using mine. Sorry I cant directly compare it to the others, but it has worked well for me. |
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Quoted:
I am fairly new to reloading... maybe 2000 .223 reloads so far. I have been impressed with the factory crimp die for several reasons. If you do found range brass, some of it can be less than perfect with dings in the neck. The FCD evens out the roundness of the neck around the bullet when the sizing die might not have been perfect at that job. It helps prevent the bullet from moving in semi auto/magazine feeding... and it increases accuracy, at least it did for me. I think the key is not to crimp too much... it only takes a small amount. I certainly overdid it on my first few rounds, but once i backed off it seemed to work as advertised. Im pleased and plan to continue using mine. Sorry I cant directly compare it to the others, but it has worked well for me. Welcome to Arfcom. 
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Quoted:
I am fairly new to reloading... maybe 2000 .223 reloads so far. I have been impressed with the factory crimp die for several reasons. If you do found range brass, some of it can be less than perfect with dings in the neck. The FCD evens out the roundness of the neck around the bullet when the sizing die might not have been perfect at that job. It helps prevent the bullet from moving in semi auto/magazine feeding... and it increases accuracy, at least it did for me. I think the key is not to crimp too much... it only takes a small amount. I certainly overdid it on my first few rounds, but once i backed off it seemed to work as advertised. Im pleased and plan to continue using mine. Sorry I cant directly compare it to the others, but it has worked well for me. Sir, run away from this forum while you can. It sucks all the money out of your wallet and bank account under the guise of "stimulating the economy" and the second amendment. Get out before they get you 
Seriously tho, welcome. Just from the 2 mods (AeroE and dryflash3) I've learned a ton, not to mention the rest of the guys on this site. A question I do have for anybody out there about crimping...I have the FCD and have it set to a light crimp. I was checking to make sure my first batch of crimped rounds loaded and ejected fine and I accidentally tried to doublefeed a round. When it jammed up against the other round in the chamber, it pushed the bullet into the case. Does this mean my bullet is seating too loose, or that my crimp should be set tighter? Or does that happen to most bullets in a doublefeed? I promise to pay more attention from now on 
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Part of the answer will depend on how you loaded the second round. Did you pull the charging handle back and let if fly like a bow string, or did you ease it back down after presenting the second round to the bolt head? If you did the former, probably nothing will stop set back there except a full roll crimp into a cannelured bullet. If you did the latter, you can probably get some more neck tension with the FCD.
Make sure you are running about .003" interference on the diameter for 5.56mm (.223 cal) bullet/case assemblies before any crimp is applied. Bullets are .224 typically, so your neck ID should be .221 after sizing. |
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Quoted:
Part of the answer will depend on how you loaded the second round. Did you pull the charging handle back and let if fly like a bow string, or did you ease it back down after presenting the second round to the bolt head? If you did the former, probably nothing will stop set back there except a full roll crimp into a cannelured bullet. If you did the latter, you can probably get some more neck tension with the FCD. Make sure you are running about .003" interference on the diameter for 5.56mm (.223 cal) bullet/case assemblies before any crimp is applied. Bullets are .224 typically, so your neck ID should be .221 after sizing. I let it fly. There was no easing in this one. That's kind of what I suspected, but I wanted to make sure. And I know this is a stupid question but I want to be 100%, the .221 diameter is inside diameter correct? |
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Quoted:
Quoted:
Part of the answer will depend on how you loaded the second round. Did you pull the charging handle back and let if fly like a bow string, or did you ease it back down after presenting the second round to the bolt head? If you did the former, probably nothing will stop set back there except a full roll crimp into a cannelured bullet. If you did the latter, you can probably get some more neck tension with the FCD. Make sure you are running about .003" interference on the diameter for 5.56mm (.223 cal) bullet/case assemblies before any crimp is applied. Bullets are .224 OD typically, so your neck ID should be .221 after sizing. I let it fly. There was no easing in this one. That's kind of what I suspected, but I wanted to make sure. And I know this is a stupid question but I want to be 100%, the .221 diameter is inside diameter correct? That is correct. That ID covers up some adverse tolerance stack-up in the die expander ball, the neck material thickness, variations in neck material hardness, etc.. |
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LEE FCD Tutorial
http://www.ar15.com/content/page.html?id=404 A FCD is NOT a MUST HAVE ITEM. Hell, I don't have one. But, that's me. 
Aloha, Mark |
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