Crimping with noncannelured bullets
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I use the Lee factory crimp die on all my 223 loads, I found it decreases ES and SD numbers noticeably. Accuracy doesn't seem to suffer as a result. I'm not using cannelured bullets.
Don't overdo it, though. I think Lee says to use between 1/4 and 1/2 turn more after die contact with the shell holder.
I found that 1/2 turn was too much, it left some noticeable marks on my case mouths.
I use 1/4 turn or just a shade more. You can feel a slight "bump" at the end of the press stroke as the crimp die petals squeeze the case mouth around the bullet.
To your questions, velocity may be slightly increased. That means pressure is probably up slightly as well.
POI is an unknown, I don't think I've fired the same load with both crimped and non-crimped rounds in the same range session.
Don't overdo it, though. I think Lee says to use between 1/4 and 1/2 turn more after die contact with the shell holder.
I found that 1/2 turn was too much, it left some noticeable marks on my case mouths.
I use 1/4 turn or just a shade more. You can feel a slight "bump" at the end of the press stroke as the crimp die petals squeeze the case mouth around the bullet.
To your questions, velocity may be slightly increased. That means pressure is probably up slightly as well.
POI is an unknown, I don't think I've fired the same load with both crimped and non-crimped rounds in the same range session.
I wondered if ES & SD would tighten up as that is what I have seen in Canalured bullets. I am already crimping canalured bullets and apply about .002-3” of crimp to the case mouth.
I crimp all my S/A pistol rounds with a lee crimper and it has made a noticeable difference with chambering and failure to feeds. I used to get about a 1% failure rate in 9mm between FTF and chambering issues. I added the Lee crimper and I am down to maybe 1 in a thousand, basically none.
I guess I will have to make up 20 rounds of the same load and crimp 10 and see what I get for a result.
Thanks for your insight Chilly
That's another of the reasons why I only use a light crimp. A heavy crimp with the Lee die is noticeably harder on the brass. I think I was using PMC or Lake City when I tried the 1/2 turn of crimp. Some of them did develop cracks at the case mouth.
I now use Lapua brass most of the time, and it's annealed after every firing. I'm up to 20+ firings on some of them, and the only failure I'm getting now is incipient case separation.
Once the dreaded line appears around the case body they go into the recycle bucket.
I came across this by accident. I was loading 32 Special rounds and firing them over the chrono to see where I was velocity-wise during load development.
Accuracy was good and I had the velocity I wanted, but I noticed the ES was higher than I usually see in other calibres. Not a big deal in a close range hunting rifle, so I called it good and crimped some rounds so the bullets wouldn't move in a tube feed rifle.
When I fired them the ES was cut in half, an unexpected bonus.
When I was having trouble getting good ES and SD in my 223, I tried the crimp and it improved things again.
Lee is often looked down on in today's world of "if it's expensive it must be better", but they do have some good products in my experience. The factory crimp die is one of them.
I think you'll see improvement in your 20 round test, with any luck accuracy will stay the same or even get better.
Most people say that accuracy on the target is the final word on load development, and they're not wrong. If that target happens to be a half mile away though, a high ES means you're going to lose shots high and low. If you can improve your velocity spread without inducing flyers by crimping the cases lightly, it's a win-win situation.
I made 10 rounds of 52g SMKs & H335 5 crimped, 5 uncrimped. The results are interesting. Both groups were ####! It was windy and apparently I am not holding up my end of the job either with a new rifle….
Anyhow, uncrimped. Crimped
Velocity. 3080. 3057
ES. 137. 65
SD. 50. 28
I was surprised that the velocity was down on the crimped rounds, with pistol rounds I find that you usually get increased velocity when you tighten the crimp. The ES and SD are both about 1/2 for the crimped rounds.
Anyhow, uncrimped. Crimped
Velocity. 3080. 3057
ES. 137. 65
SD. 50. 28
I was surprised that the velocity was down on the crimped rounds, with pistol rounds I find that you usually get increased velocity when you tighten the crimp. The ES and SD are both about 1/2 for the crimped rounds.
It's about the only crimp die that will do this well. Crimp away, but try not to overdo it. You really don't need a lot of crimp. As for POI and pressure, it won;t change it in any significant way. If you're shooting a rifle that needs ammo to be crimped, it wasn't built for precision shooting anyway. I doubt you'll notice any difference at all.
