crimping

[blacknwhite]

Whats the deal on Lee's factory crimping die? I was going to try a set of lee dies,have used only RCBS so far) and one was labeled "factory crimp". Would this be good or bad for accuracy?

 

[jo191145]

Mostly Bad.
While it is possible to see an improvement in accuracy with a crimp its generally short lived and indicitive of a flaw in the original load.
The factory crimp is basically the same as a military crimp.
They generally bite into the brass quite deeply although this can be adjusted.
Controlling neck tension which now becomes crimp tension with brass that repeatedly gets tortured is near impossible.

If you were trying to squeeze the utmost accuracy out of a 223 for example would you rather start with Lapua brass or some used Lake City brass with notches in the neck. I would go with the Lapua.

Unless your firearm requires a crimp forget about it. JMO

 

[fdshuster]

Over the last 48 yrs., I've loaded around 3000 rds for my M1 Garand, and 15 to 18000 rds for my ARs'--- not a single round ever received a crimp, and I've never had a "lack-of-crimp" related malfunction. Req'd. for military full-auto, as is the crimped-in primer pocket.

 

[varmintslayer]

Forget crimping rifle bullets.
I've read both the Lee and Sierra reloading manuals and the Sierra manual tells you that crimping is only for handgun bullets, in fact some handgun bullets don't use a crimp either.
The Lee manual is basically a selling tool for their products.
You will notice that other die companies don't sell crimp dies for rifle loading.
I have yet to meet anyone that crimps.


VS

 

[BigJim]

VS now you have meet someone that uses the factory crimp die.

BlacknWhite - the answer really depends on the type of round you are reloading for. Most bolt action rifles will not require a crimp as a general rule however there are exceptions.

The process of crimping a bullet is really for the safety of having the second, third, fourth and there on rounds in the magazine remain at the correct OAL while the recoil of the previous rounds do its work on the bullet in the chamber. You do not want the bullet to shift it's position in the case while it is in the magazine and become a shorter OAL or longer OAL becase that will change the pressure level when it is fired effecting accuracy and safety.

Rule of thumb - if it is a hot or mag load then crimp. If it is a bullet for a tube feed round then crimp. If it is for an semi-auto then crimp. If the bullet has a crimp ring around it them crimp. If the bullet is seated long and not much of the heel of the bullet is in the case them crimp. If the round is for a wheel gun,revolver) then crimp.

There are two types of crimps. By setting the seating die down a quarter to half turn you can get what's called a roll crimp. This is where the mouth of the case is turned in a bit to form a gentle crimp on the bullet. The second is a factory crimp that presses the mouth of the case onto the bullet, this can be adjusted to give a light to heavy crimp.

Part of the rational in crimping is to give the powder extra time to completely burn and bring the pressure up to get max speed by the time the bullet leaves the barrel.

Like everything else in shooting it is a matter of personal preference. To crimp or not to crimp that is the question. You will have to decide upon what type of shooting you will be doing. Hunting rounds - yes. Benchrest shooting - maybe. Competion shooting - no.

When you crimp the bullet to the case there will be some deforming of the bullet around the area of the crimp, however when you fire the loaded round this will all change due to the hot gasses that propel the bullet out the barrel.

If you set the bullet to the lands of the rifle then I would not crimp. If you set the bullet in the case to jump .02 or .01 before reaching the barrel then I would crimp.

If you shoot single shot then NO crimp. If you shoot auto-loaders then you DO crimp.

ALL factory ammo is crimped. Will you be more accurate if you do not crimp - maybe.

You need to decide what you want to do based on the type of shooting you do and what you are loading for.

To test this out take 20 rounds of whatever you shoot and load 10 with crimp and 10 without crimp. Go to the range and test them out and see what does the best for you.

Safe and happy shooting.
Jim

 

[REELDOC]

I'm on the fence with this. Jim, how much crimp is enough? I have a Lee crip die and did some test rounds. I did not like the fact that I didn't have a benchmark or a method quantify a measurement.I don't like to do things that I can't quantify. Why would not increasing neck tension do just as well? I can control the neck tension.

 

[RichAllen]

Don't crimp your rifle bullets, even if they have a canelure.




Rich