Loading some .358" Penn SWC using Lee sizing and seating dies and Lymans type-M flaring die.No matter how I setup the Lyman die I'm getting "wasp waist" bulge.Do I need to find a larger sizing die to prevent this,and if so,who's should I buy ?

Did you check to see if they chamber OK? The Lyman "M" die will leave a slight bulge for proper bullet seating.

The next question is, what size are the bullets? Are they oversized for the case?

They chamber just fine.I'm using Winchester brass,bullets mic out at .358",not sure about the case diameter.Had some replies on other forums telling me this isn't unusual as the sizing die is for .357" and the .358's will pork them up a little.I may try to score a custom sized die.

Sometimes an undersized die just happens along. since you have a mic. compare the waist on your sized case with a new unfired case. if your case is undersize, just back it out and only size the area where the bullet is to be seated. I had the same problem with a set of rcbs's, used them for a while then gave them to a friend, he doesn't know the differance, and is quite happy with them.
.... I dont think the extra.001 of bullet diameter is the reason, as most people wouldn't even be able to see it. DM

I have no experiance with Lymans "M" die. I do prefer a little "wasp waist" with handgun ammo. It lets me know that I have achived good bullet "pull". A good crimp after that, and I see good results on target and over the chronograph.

I have no doubt in my mind that "too much wasp waist" is a bad thing. It is now a question of "degree"?

Cheezywan

I turn the case expander, flaring powder through spud on all of my Dillon powder measures so that I will have that wasp waist in the case. I can look and see where the base of the bullet stops in the case.
It shows me that I have a very firm grip on the bullet as well as insuring that under recoil in a revolver the the bullet will not get seated any deeper.
Another positive of the wasp waist is the bullet is gripped very well by the case in addition to the roll crimp. I get very good powder burning, little residue. All in all a good thing.
Jim

Like the others, I've found that if they chamber OK, don't worry about it.

I have had trouble attempting to "neck size" .44s, though. While sizing the top half with my carbide die, the downward force bulges the bottom half out a little bit, and then that brass won't rechamber all the way. I was surprised by this, because the force required to resize doesn't seem all that great.

So I could (theoretically) raise my resizing die up so it'll just resize the top where the bullet sits;Then I could just run them thru the Lee Factory die to ensure they'll chamber ?

Wasp waist is no problem. You could try neck sizing the case but I couldnt really find any advantage to it. In a revolver the chambers will vary a little and the fired cases may not fit in all chambers. I like to be sure the ammo will fit under any circumstances. Just my .02. To answer the above question: yes. The Lee FC die is designed to make sure the round will fit in the chamber.

So I could (theoretically) raise my resizing die up so it'll just resize the top where the bullet sits;Then I could just run them thru the Lee Factory die to ensure they'll chamber ?

Why go through the extra step if your reloads will chamber now???

Not unusual for carbide dies to produce wasp shaped reloads. Was a little annoying when I first started resizing with carbide dies since any noticeable reduction in case diameter from my .38 steel sizer dies occurred only at the casemouth. My carbide dies reduced case diameter almost all the way down to the web.

Have since found out that with carbide dies, the bullet is still gripped firmly, everything chambers, and there are no problems with accuracy attributed to the reloads. Your reloads may look a little strange at first but you will probably be the only one to pick up on this. If you attempt to back out your sizer die to only reduce casemouth diameter, you may bulge the lower part of the case as gmd3006 said. I say shoot your reloads for a while and see if this isn't true. Believe you will find out that appearance will not affect accuracy.