I have tried the lee .223 dies and not to happy with them. I am sure it was me and not bashing lee by any means. I now have a short base .223 dies I decap and expand in one die then if I do not I have a boat tail bullet I crush the case. Do I need a "M die" for flairing the case to accept a flat based bullet? Also the RCBS dies I have taper crimp as well, that is what I want for my AR. Right now I am just plinking until I get the hang of all this and understand the lingo. I would like to get into some quality loads down the line. I bought a rock chucker at a garage sale along with a ton of reloading stuff such as about 4k primers, scale, case trimer alot of new .270 win cases and bullets and about 500 .224 50 grain flat base bullets along with a bunch of Dies. paid 150 for it and everything else I am leaving alot of it out as its nothing I use yet. So back to my original question do I need a M die and if so does RCBS make one? TY

I think Lyman make the "M-die".  See if this is what you're looking for.  

A M type die is normally used with cast lead bullets to keep from damaging the base of the soft lead bullet during seating. I have been reloading for over 45 years and never used a M type rifle die or a small base die. If you are crushing your necks during bullet seating you are not de-burring the inside of the neck enough, not trimming the cases to the correct length or have your dies improperly set up.

I would advise re-reading the die instructions and also reading the front part of your reloading manual that explains so much about reloading.

1. Double check your case mouth de-burring.
2. Make sure your seating die is not set too low and trying to crimp and seat at the same time. Make it a two part operation, seat your bullets first and then go back and crimp by setting the die down until the desired crimp is achieved. (you get a better crimp and accuracy with a two part operation)
3 Setting the seating die down too low will crush your necks because the die is squeezing the case mouth making it too small for the bullet to enter.

All the information in the world is written in books and all you have to do is read.
Attila the Hun

Either use a Lyman M or Lee Universal Flaring die for FB bullets.

When you trim the brass it leaves a small burr on the inside and the outside of the neck.  
These must both be removed with an inexpensive tool called logically enough, a case neck burr removal tool.  One end is a tapered to a poing and de-burrs the inside of the neck.  You hold the case in one hand and turn the tool by hand or in a drill press and just touch it enough to remove the burr AND make a small ramp so that the bullet seats easier.  A little bit here is all you need.

The other end of the tool isconcave and serves to de-burr the OUTSIDE of the neck.  Again just turn it about a full turn or less and the burr is removed.  

You should be measuring your cases after resizing with a calipers tomake sure it is not too long.  I usually have to trim most every time (and then de-burr)

You may have other requirements to get the bullet started in the case, but de-burr is really mandatory after case trimming.

hope this helps,

Bill

^^^This^^^

I discent to the popular school of thought.

Case necks should be chamfurred inside as I do all my precision rifle loads.

Deburring, chamfuring is a basic part in hand loading process..

-that said-

Your question regarding M die deserves more merit than being given.

I use an M die for brass trimmed with Dillon trimmer for all bullets including flat base.

It works well and quite a few who trim with Dillon RT1200 trimmer use M die with success.

-however-

I agree with dryflash3. You need to slow down a bit and absorb some basic principles of reloading.

I've never had need of a small base die for AR brass. If you feel a need to size small base you're working brass hard. Look into annealing.

eta. I load .223 with several brands of dies. These would be Dillon, Hornady, RCBS and Lee.

I've used Lee RGB, .223 dies to size and seat rifle cartridges that flew 500 + meters before ringing 26" steel plate.

Your issue is likely the handle puller, not dies.

I agree problem lies with me. I have played with it a bit now and seem to have a much better grasp on it. I did sixty 55 grain hornadys and ten 69 grain sierra BT will up date as to how I make out with them. Thanks for the advice