Issues Reloading .40 S&W

I'm sort of a newbie to reloading and I'm having trouble reloading .40 S&W

I'm using an RCBS rock chuker with cabide dies a uniflow and 10-5 scale to reload for my .40 s&w

I'm using once fired brass mosly CCI and remington UMC cases
I'm using Alliant Unique powder at about 7.5-8.0gr
I'm using nosler 135gr HP

my issue is I need to flare the case to an extremely big mouth to allow the bullet to seat to a Case OAl of 1.130" is this normal and on more than one occation I've actually had the case walls collape or wrinkle do to the force required to seat the bullet properly

so here are my ?'s
how big should the case be flared to allow a propper reload?

why are the walls collapsing

any input would be greatly appreciated

Romarm SAR-1 7.62x39
Ruger 10-22 .22LR
Mossberg 500 20ga
Weatherby Orion G3 20ga
Weatherby Vanguard sporter stainless 7mm Rem Mag
Ruger Gp-100 .357mag
S&W sigma .40s&w
2 Sterling Stainless .22 LR's

"The strongest reason for people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.” — (Thomas Jefferson)"

 

You should only have to flare the case mouth enough for the base of the bullet to fit.

Belling it any further will shorten case life, and not enough, well, you found out, the case will crumble.

As for OAL, don't let the books get the best of you. The actual OAL of your final cartridge should be one that allows a full magazine to fire without any problems. And this totally depends on the bullet you are using, your magazine dimensions and your chamber dimensions.

 

ricciardelli is correct about oal. But it needs mentioning that if you go below the listed oal(over all length) you will increase the pressure. The 40 is already a high pressure cartridge so you need to respect the min. oal. As to length you can go to the max. COAL over that and you will start to run into problems getting the rounds in the mag.