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Posted: 2/26/2011 1:45:05 PM EDT
| How much effect does no crimp have verses say a taper crimp and or a roll crimp? Not talking about how well it holds the bullet how does it effect pressure or velocity when fired. |
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Now that's the $64 question! I think however it is safe to say that no crimp is the best thing to do for accuracy and that can be verified by the fact that benchrest shooters never use a crimp.
The reasons to crimp are to keep a bullet from pulling out of a case as in a straight walled revolver round under recoil, or to keep a bullet from being shoved into the cartridge such as in a tubular magazine rifle. I'm sure there is some effect on velocity from crimping but I believe you'll have to do your own testing to figure that out. |
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how does it effect pressure or velocity when fired.
Generally you'll expect to see an increase in pressure and velocity (unless it so/too tight in the case that it's stuck or near welded in there.......bad things can/could happen.......OMG). But........... How do measure the amount of YOUR taper or roll crimp vs MY crimps? You see, there is NO exact answer in fps. Just know that generally some like to use............. Proper neck tension is enough for a match bullet. BTW, match bullets don't usually have a cannelure. Then, enough is enough when you don't get bullet set back or have the COAL grow when chambering. Besides some worry that if/when they crimp, they'll end up damaging the bullet's smooth surface. If there is a cannelure, some will still omit the crimp. Then, some will crimp in the cannelure because it's there. And, crimping in the cannelure could/can ensure against bullet set back (very important to the military). And, even if there is a cannelure.........it doesn't mean that you have to crimp it there. Some ignore the cannelure and go for a specific COAL. Some like a FCD on everything. It's their choice. BTW............rifle bullet crimps are usually refered to as a taper crimp NOT a roll crimp. The words "roll crimp," is usually used when talking about pistol cartridges. And, yes, the pistol cartridge's roll crimp is usually much heavier in comparison to a taper crimp. OMG.........but, you probably already knew this. So, say it this way........it's not written in stone that you must or mustn't crimp. Aloha, Mark |
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Quoted:
How much effect does no crimp have verses say a taper crimp and or a roll crimp? Not talking about how well it holds the bullet how does it effect pressure or velocity when fired. Not enough info for a good answer. Rifle or Pistol? Caliber and type of gun? |
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Quoted:
I use a Lee Factory Crimp die. I found that using a light or medium crimp gave me better ballistic data and helps with bullet runout and a littel higher bullet speed (5 to 10 fps). That's IMHO. Mike I saw the same as Mike using the FCD, and was called a liar here for saying the FCD tweaked bullet runout LOL. But according to my runout gauge's it did what it did. The FCD simply made a great shooting 223 69gr load I have been using for 30 years a little better. This is what my runout gauge,chrony and target's told me. I.m just passing along the info lol. |
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Slightly OT but related would be to remove your primer with a universal decapper then when you FL size the case remove the neck expander altogether from the die.
This makes for a tight case mouth opening and can only be done with boat tail bullets (Flat base would require a neck expander die to flare the mouth and prevent shaving copper) This improves accuracy in any die that does not have a perfectly aligned expander ball simply because only the sizer walls are affecting the case. If you have ever crunched down on a berdan case by mistake or have done anything to misalign your expander ball and decapping pin rod this will make for a more concentric neck and improve consistency. There are sizing dies that are sold specifically for this but I found just removing the decapper does the same thing. While this adds a step by decapping then resizing separately the resizing is faster. Another of those bench rest accuracy tricks. You certainly don't need to crimp with this method nor worry about bullet set back in the magazine. Wulfmann |
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Quoted:
Quoted:
I use a Lee Factory Crimp die. I found that using a light or medium crimp gave me better ballistic data and helps with bullet runout and a littel higher bullet speed (5 to 10 fps). That's IMHO. Mike I saw the same as Mike using the FCD, and was called a liar here for saying the FCD tweaked bullet runout LOL. But according to my runout gauge's it did what it did. The FCD simply made a great shooting 223 69gr load I have been using for 30 years a little better. This is what my runout gauge,chrony and target's told me. I.m just passing along the info lol. When I am testing rounds I always use new Lapua brass and match grade bullets in my rifles. I found that heavy walled mil. spec. brass cases can have .0004 to .0006 of runout in the wall thickness in the neck of the case. If you turn the neck down they work well for stooting practice. There is a lot work( like sorting, weighting componets) that goes into making a true match grade round. That's IMHO. Mike |
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a good read here http://www.ar15.com/content/page.html?id=404 |
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