Has anyone here or are there outside sources that have proved out Lee's theory?

Lee's theory:

"Tests demonstrate that even bullets with no cannelure will shoot more accurately if crimped in place with the Lee Factory Crimp Die. A firm crimp improves accuracy because pressure must build to a higher level before the bullet begins to move. This higher start pressure insures a more uniform pressure curve and less velocity variation. Even powder selection is less critical. Until now, handloaders seated the bullet to touch the rifling to achieve similar results. This is not always possible nor desirable."

Some people are just never going to be convinced of anything unless they do their self and half of those can't even convince their self of what they already know.

Just buy ONE for your self tighta** and try it.

I'll take this as NO, you have not tried it.

Didn't do anything for me and if you over do it you will get wonky case necks. But it has worked for others so I can't make any hard and fast claim.

Why do you want to crimp? If for a hard kicker or auto maybe yes but for anything else adjusting neck tension is better and I would invest in a collet die before getting a crimp die if accuracy is the objective. Lots written on how to tweak them for best work.

Whether the claim is accurate or not is not for me to say, but have played a lot with varying neck tension which in my book is kinda like crimping, depending on your definition of crimping. Some things make great changes, and others not so great. Always found that 2-4 thou tension is adequate under most circumstances. Anyway a guy over on accurate shooter did a small sample test matching your question. Take the data for what it’s worth. I didn’t see any drastic enough change to brag about.

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

Mine reside in the junk box

I use 'em for every caliber I load for. 44, 357, 9mm, 30-06, 45-70, 223, 10mm...

Now, do you know any more than you did when you started the thread? Some people like 'em, some people hate 'em. You don't know any of those guys, so who are you going to believe?

I'm in the "some people hate 'em" camp.

If you make straight ammo with proper neck tension, they are not going to help you.

If the LFCD makes you ammo shoot better, go back and address the other two variables.

I use them on all straight wall cartridges, it’s just easier and more forgiving if your cases are not all trimmed perfectly. 44,454, 357,45-70, etc

I also crimp every semi-auto rifle load with one, because a setback bullet can ruin your day. As far as accuracy, I noticed no difference in my bolt rifles so I don’t use them for those rounds, but it didn’t seem to hurt either.

I know most people don’t crimp rifle rounds, but I’ve had .223 bullets get set back because they didn’t feed properly out of the mag in an AR so I’m probably over anal about it. I know plenty of folks that don’t and get along fine.

I've tested otherwise identical loads in bottle neck cartridges that were crimped with the Lee die and uncrimped using bullets with a crimping groove and the bullets seated to use this groove. The result has been the same the three or four times I did it: The crimped loads shot slightly worse. I use it when I have to crimp such as a .30-30, but not otherwise.

Consistent neck tension is key to accuracy. If you don't know how to accomplish this through annealing and proper sizing, the Lee FCD may be a shortcut for you. I never could accomplish with it what Lee stated. I had better results annealing cases.

I use them for 223’s I shoot in AR’s also.

I use them to put a crimp on cannelured bullets mostly. A second die for crimping comes in handy and the LFC die performs that task.

You have to work up loads using a crimp die because it does change pressure. If you try and use the crimp die with an already developed load, then accuracy is out the window.

I saw an accuracy increase when using the factory crimp die with the 22 Hornet and K Hornet, otherwise used them on 30/30, 35 Rem, and 444 Marlin.

Swifty, thanks for posting info.

In the context of my question, did you test for accuracy on crimped versus non-crimped?

I did.
That’s why there in the junk box

I use them for 5.56, my M1 Garand ammo, and my Rem 350 mag. I have no idea which works best, crimped or not.

Didn't need to.

I shot and reloaded all those same ammunition for decades before I ever first tried a Lee FC die.

I didn't buy the next one because the first one was worse.

If you are crimping to a cannelure rarely did that coincide with the most accurate seating depth. The Lee worked better crimping this way. When not using a cannelure I felt the crimp distorted both the bullet and the neck which can't be good for accuracy even if uniform.

Here's one more opinion.....they have their place. I own a few that I use for 357 and 44 magnums, .223 for my AR, and 45-70 and they do a great job. Beyond that, I have never really seen the need and think increased accuracy for most calibers is better achieved other ways.

I loaded 20 of a proven load for an '06 sporter of known accuracy, crimped 10 and launched all 20 at alternating targets. Results: SD went down significantly on the crimped rounds but groups sizes remained statistically similar...within 1/10 of an inch. Conclusion for my rifle, waste of time since I don't shoot at game at long ranges. SD means nothing to me at 250 yards.

I use them in all of my larger bore five or sixguns. I knock out the carbide ring though.

I am convinced that you have to try it and see. The crimp die worked for my 303 British No 4 MkI's, but that could be because of their longer, worn throats. That, and my brass hadn't been annealed in a while. My 30-303 rifle, used today, has a new Shilen barrel, and I used freshly annealed cases.

The math junkies won't like this, but I loaded up 100 cartridges to test the effectiveness of the crimp die for my 30-303 book. 50 were crimped. 50 were not. The crimp was light. I think most people apply too much force when crimping.

The load consisted of a .308 dia. 150 gr. Remington PSP FB bullet, IVI cases, annealed and trimmed to 2.210 inches. Win LR primers. 46.1 gr. IMR 4895 powder. COAL - 3.040 inches.



Stats:

5x10 shot groups were fired. both crimped and uncrimped..

Avg group size - crimped - 3.06" at 100 yd.
Avg group size - uncrimped - 2.35" at 100 yd. 23% smaller.

I believe annealing makes a bigger difference on group size than crimping. Cases that are regularly annealed will make smaller groups. This is based on years of annealing and testing with various cartridges, including the 308, 222 Rem, 30-30 and some others. Now the 30-303

Avg velocity for 50 shots - uncrimped - 2708 fps
Avg velocity for 50 shots - crimped - 2703 fps

In the photo, crimped on the left. Uncrimped on right.



With the exception of compressed loads, I probably won't bother crimping for my rifles anymore.

I have a load for 150 grain SSTs in 308. I tested crimped verses uncrimped. The crimped had higher velocities, and better accuracy over the uncrimped.

Crimped: Avg 2836, SD 13
Uncrimped: Avg 2778, SD 16

I dont crimp the match bullets without cannelures, but those SSTs get crimped.

Good test. How were the cases resized?

Thanks. I used a body die and a Lee collet die.

i used a a lee crimp die on my hunting brass ,my reason is regular brass is not as uniformed as like Lapua brass so it does help to use a neck crimp die on regular brass and it kinda uniforms the neck a little around the bullet for better acuracy.plus Barnes bullets also recommends to neck crimp some of their bullets .

I use them on EVERY lever gun

I have will explain later got a day planned. Tag.

I don't tend to crimp on bolt guns anymore, but I did once in awhile with some '06 rounds in the past using the LFCD and got some really good results.

As I mentioned in another post, I use the Lee Crimp in straight wall cartridges for pistols and any cartridge for tube magazine lever rifles.

I crimp on the Cannelure and my motivation was two fold. First to keep bullets from moving into the brass on tube magazines/cylinders on recoil, second, as part of the load process to minimize crushing thin wall cases such as the 44 WCF. Both reasons have worked for me. I note that I use the Lee instructions as to how much crimp is to be applied.

I do not use a Lee Crimp in bolt or single shot rifle cartridges; though if I was loading heavy recoil rifles such as the large 40 caliber magnum calibers and hunting dangerous game, I would consider it, but again would look for a cannelure to apply the crimp.

My recoil reason above has been a little thin because I do not use a Lee crimp on my 99F Savage in 358 WCF. However, after one occasion of having recoil move bullets on neck sized cases I now always full size the 99 loads but do not use a Lee Crimp.

As for improved accuracy I am a skeptic and give more credence to the mystery of primer, powder, bullet and barrel as the key in the quest of accuracy.