I recently started crimping some loads for my 470. Prior to doing so I was shooting a load that generated bullet speeds of 2125-2137 FPS. When using that same load with a crimp, the speed picked up to 2169-2171. Is that a normal occurrence?

There should be a rise in pressure with some types of bullets when crimping. I am not sure if the moderate rise in velocity outperforms the loss in accuracy. If you really feel you have to crimp, be careful to trim your cases at the same length and use a special crimping die like the Lee Factory Crimp Die

I don't know where to find a crimping die for a 470 (I have one for a 375) so I'm using the seating/crimping combination that my RCBS dies offer. I guess it's working properly as I can feel the resistance when the crimping is supposedly taking place, but I cannot see the crimp on the case as I can when I use the Lee.

assuming strong crimp, yes, and yes... and yes, it is SUPPOSED to help standard deviation too

jeffe

quote:

I am not sure if the moderate rise in velocity outperforms the loss in accuracy.

I use the Lee Factory Crimp Die on all of my loads. There is not only NO "loss in accuracy", there is an increase in accuracy.

Here is a link to Saeed's test using the LFC die. No loss in accuracy found.

http://www.accuratereloading.com/crimping.html

Thanks for the link Steve. As I understand the results, most of the work you have to do is case preparation. You will get better results only when you select your cases carefully from the same lot, trim them, heat treat the neck measure and if necessary reduce the thickness of the neck's wall.
I use the Lee die too for special purposes. The .224 impala bullet is not held sufficiently by neck tension alone in my 22-250. Her crimping provides consistent results.

I just ordered Lee factory crimp dies for .416 Rigby, .458 Lott, .470 NE, and 500NE. Lee requires you to send them a dummy loaded round for each caliber requested, if it is a non- stock caliber like the above mentioned ones. They charge $25 for most calibers, $50 for the nitro express dies. BTW the NE dies are large body dies, which is not a problem if you have a press like the RCBS Rock Chucker Supreme with threaded insert which can be removed to use the large body threads beneath.

If you have any questions contact Dave at Lee Precision, 4275 Highway U, Hartford, WI 53027

I can't find their e-mail address right now but do a search it'll be easy to find. Dave was very helpful and always followed up promptly by e-mail. Hope this helps.

Geronimo

There is a report on crimping right here at "accuratereloading." Just look for it at the home page.

I don't use any special dies when crimping, but the standard die, whichever brand. For example, I have a .338WM Redding 3-die set, and it comes with instructions for crimping. All I have to do is to make sure that all the cases are trimmed to the same length, and then adjust the die on an empty case until I attain the exact crimp I desire. That's all there is to it. If all the cases are of the same length, the crimp will be identical on all.