So since 40 SW requires a tapper crimp can I use the Lee Factory Crimping die and still be able to run the ammo through my semi auto?

What you do is flare the case MINIMALLY and you will not need to crimp at all. Most bullets have at least a little bevel at the base so the flare doesn't have to me much at all.

Yep. leeprecision.com/carbi...w10mm.html

Yes, you will be fine with the Lee die. Crimping makes sure that the bullet doesn't get shoved back into the case or work forward under recoil. Granted, a properly sized case provides a certain amount of tension to help hold the bullet, but since all cases (and bullets) aren't created equal a crimp is necessary for reliability and, in many cases, safety. And, as Grumulkin mentioned, minimal flaring of the case helps as well as not working your brass as much.

Grumulkin...You are correct, but you still need to do at least a pliminary crimp to insure that there is no flaring left or that occasional round will jam when feeding.

The Lee FCD die is a very good way to insure this.

tlo7mm... Am wondering why you don't use the seating die to remove the bell. Lee dies for 9mm, .40, and .45 already have a taper crimp if set properly.

So, tell me, under recoil does a bullet go further into the case or further out?

It is a trick question by the way.

Once again, you do not need to crimp 40 S&W bullets for either dependability or safety as long as you flare the case minimally. I actually load for a 40 S&W so should know. I also load for things that do require a crimp like a 460 S&W Magnum and a 454 Casull; for those I've found the Lee Factory Crimp die to be essential.

My flaring, by the way, is so minimal that there is no residual flare when the bullet is seated.

The only bullet movement I have suffered is having to chamber the same cartridge over and over. Other then that no problem.

All of my 9mm X 19 and .45 ACP cases will have some percentage of crimp depending on how much flare is left after seating. You must remember that most (if not all) don't trim straight wall cases [as I do] and therefore some cases will be shorter and some longer. I, also, use no more flare then is necessary to start the bullet.

As to your "trick question" It's called "bullet creep" and can jam a revolver, but really will not do much in a semi-auto except cause a failure to go completely to battery.

Yes, in revolvers, bullets move forward under recoil.

In heavy recoiling rifles where cartridges are in a magazine, the bullet can hit the magazine well and push it further into the cartridge.

Not suffered that problem with rifle box magazines nor tube magazines. Bowning A-bolt .30-06 and Winchester M94 .30 WCF (.30-30)

If you set your die up properly, keep your cases trimmed to the same length, and use just enough bell to start the bullets then the die will return the case mouth to the right dimension and remove the bell. Essentially the bullet seating die will put a very light crimp or just remove the bell when it is set up right.

If you want to spend extra mone to get another die you are free to do so but it isn't necessary for reliable feeding or function.

Yup...What I said...

Now I have wedding dresses showing up on my huntingnut. Gotta have a talk with the wife. I already told her we were not getting married again.

So I have an RCBS carbide die set, you are saying that I really do not need to invest in a Lee FCD. I was just curious if it was a wise investment or an unnecessary one.

Way I see it mate...it is a wise investment...but not really a necessary one. It really comes down to what you want. Set you RCBS Die up correctly and it will do the job for you nicely...A Lee FCD will also do a great job.

It's really your call mate, and armed with the info provided above it should be an easy decision.

Take a factory round, and measure the case case at the top. This will give you the crimp of the round. Set your die to that measurement. If you are loading lead, then use a little less crimp.

All you really need to do is iron out the flare.

I run a Dillon 1050 in 9mm, 40S&W, 38 Sp and 45ACP.

I should have been more specific...Yes, the flare can be removed and the case crimped using only the seating die, but if using cast bullets it is better (in my opinion) to use the seating die to only seat the bullet while using a separate die (such as the Lee) to perform the final crimp and make sure all cartridge dimensions are correct. Lead bullets have a tendency to "shave" as the case is closed while still traveling upward, as is the case when using the normal seating/crimp dies, which can cause head-spacing problems in "rimless" cartridges if not removed. Not such a big deal with jacketed bullets, but it can still happen.

And Yes, recoil causes the bullet to move forward, but slamming into a feed ramp on a semi-auto can cause the bullet to be seated deeper which can cause pressures to skyrocket. Always safer to have a firm crimp on such rounds.