I have a question that has been a topic of discussion. How much difference in pressure is there between a noncrimped cartridge and one that has a med to heavy crimp on it???? we are talking a 300 wsm. and has anyone determind how much of an incress?
Old Timer

Glad to see this topic come up. I've been debating the idea of crimping or not? I've not crimped for any cartridge, except for the big stuff, .375 and above.

Should I be crimping and why?

Bear,
I have never crimped before untill now . I could not get my 300 wsm to shoot a tight group, so started crimping and it would seem to have done away with the fliers. my group are all under .5 for 100 yrds. When I get to go home to Wyoming I like to hunt with my 338 Win and I am thinking about crimping but am not sure about how much this raises the pressure.

Old Timer

"it depends"...

i've seen some guns that crimped tighten up groups and SD of veloticy...

I only crimp for tubular magazines and heavy revolver cartridges.....and never lacked that I know of.....you do as you think best as crimping don't hurt anything either.....one of the first things you'll notice is that many rifle bullets don't have a cannelure to crimp into.....that should serve as a hint to something.

Here is a link to Saeed's test using the Lee Factory Crimp Die.

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

The Lee FCD does not require a cannelure to work.. I use it in all of my calibers and have found it to increase accuracy and reduce SD.

I don't know how much difference in start pressure there is between between crimped and uncrimped, assuming done by LEE FCD but I'm sure that reloaders of even minimal experience have noticed there is sometimes (often?) varying pressure required to seat bullets in cases which is why I crimp with the FCD firmly.

I would say if you are worried about crimping causing too much of an increase in pressure, Your loads are way too hot to start w/.

Most Factory ammo has a stout crimp. Looks to be much tighter than the LFC crimps but, I haven't compared them side by side while pulling bullets.

I don't think you should worry at all about the crimp causing danger. If it has helped your groups like you say, I'd load em' that way from now on.

I wonder if Lee is going to make the FCD fro the WSMs?

Good Luck!

Reloader

Thanks For the replies,
I don't think I was worried about to much pressure just curious.
It would stand to reason that the pressure on a heavily crimped case would be more and therefore change the point of impact.
Old Timer

quote:

Originally posted by vapodog:
that should serve as a hint to something.

So, factory loads with out cannelures arn't
crimpt?? Don't think so.
JL.

quote:

I wonder if Lee is going to make the FCD fro the WSMs?

They do now. I have had a LFC Die for my 300WSM for almost a year. At that time Lee's web site did not list FCDs for the WSMs, I found it at Midway.

I posed the question to Mark Lee and his reply 10 years ago was the the peak pressure decreased slightly on average while the total pressure curve increased 5%. The major difference, he found, was change in point of impact. The rifle has to be sighted in for one or the other.

I agree with Reloader. I only crimp in my 3030 and do not experience any detectable pressure differences (using my eyes and PRE). I actually found that velocities for crimped were on average, 10-15fps lower, which would support my observations.

Deke.