Fine tuning loads lee factory crimp die

[Warbird2006]

Collet crimping (FCD) and increased neck tension TYPICALLY reduces velocity due to more energy being spent releasing the bullet from the case. A collet crimp, or increased neck tension, will also reduce ES because it makes a more consistent contact with the bullet, resulting in a more consistent release.


I use a Lee FL die for several cartridges. I remove the expander ball from it, using it FL size the outside dimensions of the case. Then, I use a mandrel in a separate step to set final neck/bullet tension. My tension is right at .003" and is extremely consistent throughout the length of the neck thanks to the mandrel.


I also turn my necks too, but that's not really necessary when using a mandrel. It's just something I do out of anal retentiveness.


You can get a mandrel setup from somewhere like K&M. You can get one machined to the exact size you want to give you your desired amount of tension. A mandrel and the press adapter are $30 or less.


Use that along with your Lee FL die and a quality seating die, and you can make very consistent and accurate ammo for pretty cheap.


At .003" of tension, you don't need a crimp. I don't crimp any of my bottle neck cases and I run semi-autos as well bolt action. They run very consistent, cycle smooth, and I get no bullet setback. My SDs are under 5fps and my ES is below 10fps.


While increasing uniform neck tension can increase your accuracy and decrease your SD/ES, so can utilizing a FCD. It's not as superior of a method though. Collet crimping puts peak case neck contact with the bullet only on the point of the crimp. If the bullet gets bumped, it's compromised. It may no longer be consistent with your other rounds. Mishandling of the rounds, rough cycling/feeding, etc is all it takes.


By setting your entire neck to a consistent amount of tension, you don't need to crimp and it makes the point if contact with the bullet uniform throughout the length of the neck and bullet's bearing surface. That means it's not easily bumped out of round

Interesting, my crimped loads are faster, I believe due to increased pressure.

 

[coop2564]

Yep

 

[Mike AVM]

I use one on most of my loads. I don't own precision rifles, only ones used for hunting. Anything 338 WM and over I crimp. It doesn't dramatically change things but I know the seating depth I found best accuracy with will remain consistent under recoil. I also don't neck turn except for a tack driver 22-250 I own. All my crimped loads are sub-MOA. With me shooting, and that's the big variable, I have crimped loads in standard hunting rifles that hit the 0.4-0.5 range. Not every rifle and bullet combo will do it but the OAL remains consistent. There are many ways to do the "accuracy" thing and I'd do what works for you. Experiment. It's a hobby!

 

[Mike AVM]

Here's another excerpt from my notes where I've discussed this before with someone:

I can tell you why you're getting better consistency. You're getting more consistent neck tension. The collet on the FCD is applying a consistent amount of neck tension on the mouth of the case.

Nathan Foster has a section in his reloading book talking about it.

I've experienced the same thing, and after reading his book, it all makes sense now.

Consistent velocity is derived from consistent neck tension and consistent pressure, as well as proper bullet to bore concentricity/alignment.

I myself have gone the route of annealing and using a mandrel. I have also experimented in the past with the proper size bushing die, but to achieve true uniform neck tension throughout the length of the neck with a bushing due, you really need to turn the necks to ensure the thickness is even and you're not applying more tension on one spot on the bullet that is more than another. I get great velocity consistency annealing and using a mandrel to see final tension, and I don't have to worry about crimping.

Crimping can actually reduce velocities. More energy is used to release the bullet and thus velocity is reduced. That's a big reason why I don't like to do it. I've never had an issue with bullets moving from recoil.

If you don't anneal, using a FCD is a great way to essentially cheat at getting consistent neck tension. It's essentially a crutch.

Too much crimp can give negative results though. That's why if you're doing a crimp, it's best to experiment and find the best amount of crimp that works best. It's also imperative that all your cases are trimmed consistently to the same length as different lengths will result in different amounts of crimp.

Yep, I anneal and use a mandrel. That was a big change regarding consistenecy and lack of flyers.

 

[Mike AVM]

One other note, the annealing of cases is critical. If the neck is work hardened, you'll never get consistent neck tension. I anneal after 2nd firing. It's a pain but in conjunction with a mandrel, it produces consistent results. I then use a Lee FCD to keep everything right where I want it. You don't need an excessively heavy crimp.

 

[JDD]

Just checking in. I have not gotten to move forward. I had my prostrate removed 4.3 for stage 4 cancer. End of May test confirmed no cancer. 6/1 started feeling like ****. Left the wife in fla to watch grandkids . Last Monday took everything to get to er. a major infection showed up were a lymph node had been removed. I been on IV around the clock since. It may be a month or more to get back up and running . It's that so called
MRSE ( not sure of spelling) not something to play with

 

[WildRose]

Just checking in. I have not gotten to move forward. I had my prostrate removed 4.3 for stage 4 cancer. End of May test confirmed no cancer. 6/1 started feeling like ----. Left the wife in fla to watch grandkids . Last Monday took everything to get to er. a major infection showed up were a lymph node had been removed. I been on IV around the clock since. It may be a month or more to get back up and running . It's that so called
MRSE ( not sure of spelling) not something to play with

Glad you got the cancer under control, the post op infection should be a breeze compared to dealing with that.