357sig reloading
igoodness, benzuncle has said pretty what i was going to say. I also started 357sig without anybody's direction, and I concur that 45acp is a Much Better round to start on--for lots of reasons. The 357sig is a high pressure round and can be unforgiving. I HIGHLY recommend AA#9 as the only powder to use (with 357sig), especially when you are still learing. The reason is that it pretty well fills the case and allows only a very small amount of setback. I have both lee and rcbs dies and there's little difference between that I can tell. The Shell holder needs to have .008 to .011" taken off to allow the result to have the proper HS. Everything you read will tell you that the shoulder does not determine HS. That is not quite correct, if the should is far enough forward. Both the Lee and RCBS sizers that I have result in that condition. That's why I ground off the top of my shell holder. (BTW, I have another Lee #19 shell holder that's ground off by a lot more, along with a 40sw sizer die that has as much ground off the bottom as I dared! This was to eliminate the Glock Bulge near the head of 40's, and also to some extent, 357sigs--I use the 40 sizer as the first step for the 357. If you don't do this you have to lube every round. I don't like to do that). If you don't push the shoulder back where it belongs you actually lose some neck length. This was about .011" in my case. I don't know if it is significant or not, but it makes me feel better to have that little bit more neck to grasp the bullet.
There is one other biggy on 357sig--that is the bullet. I have only found 3 that work well for me. Those are the Speer "357sig 125 JHP" and its TMJ counterpart. The next is the Berry 124gr hollowpoint. It is plated and not really rated for the speed, but I've not yet had a problem with it at velocity up to 1450 or so. The third is the XTP 124. (Actually there is a fourth--Montana Gold has a clone of the XTP which is a lot cheaper). Most of the other 9mm bullets I have used don't have enough cylindrical ogive--and the part that is in the neck is starting to become undersized. They are a disaster. (Although I tried some with max charge of AA#9 and got away with it due to high compression of the powder!).
The part about crumpling the cases sounds like you are not flaring (or bell-ing) the round. You will need to use a 9mm flaring die for this. You will need a die set for 9mm someday anyway, so go ahead and get that one. And when you order it, get a Lee Factory Crimp Die for the 357. That will correct mild "crushing" and otherwise make thiings chamberable that wouldn't otherwise.
357sig is a lot of fun. You can see in one of my posts that the .400 corbon has similar issues but IN SPADES.
Best of luck,
Dave