There is 1 internationally agreed standard (2 if you include Champagne) for crown closers, all bottles are made to fit the caps not the caps made to fit the bottles.
This is an urban myth; we represent are such a small proportion of the beer produced that the big breweries dont give a stuff about us.
Get a new capper or a new bell, the one you are using is worn out.
You should have checked your calendar... You're 3 days late for April Fool's day. :blink:
Seriously I doubt that we'd even trouble the megabreweries.
Is the trouble you're talking about is the neck snapping on the bottle?? You're not using one of those 2 lever cappers are you? If so toss it. The jaws would snap the neck off anything. If this is the case grab yourself a bench (single lever capper). If this is not the case then follow MHB's advice and replace the bell on your existing capper.
Do you use twist tops? I don't bottle anymore, however I tried to use the 2 lever, metal jawed job that came with my Coopers starter kit 9 years back and it was forever breaking the necks on 375ml twist tops.
OTOH Once I moved up to a Superautomatica bench capper they rarely broke.
As for using the two lever on stronger (non twist top) bottles I'm not sure as I never tried.
I see where your comming from. I mainly used 375m Hahn Premium bottles (non twist top) as the glass is thicker. Shame they are now 330ml as I had non-home brewers giving me supplies.
My longnecks are 750-800ml twistops and I also haven't had any problems with these. I don't think I have ever used it on a 375ml twist top but I did use the capper that you hit with a hammer on a 375ml twist top. Knowing how thin some of these bottles were I always used this type of capper with caution.
I suppose this is why they introduced PET bottles.