I destroyed my 629MG 4.5 yr back with a slow to release bullet. The load was a Magnus 300gr LSWC over 6.2gr Titegroup in a .44 Magnum case yielding 820 fps. The problem was what I had been shooting previously that day - .44 Russians and Specials - 200 of them. The long .44 Magnums had to be shoved into the chambers - I knew better. The physical maximum charge one could put in that case and still seat that long 300gr LSWC was ~10 gr - 11 gr was safe, according to Hodgdon's. 12.4 gr was impossible - I actually tried... but over 10.2 gr started compressing the propellant and offering significant resistance in pulling the lever on my Dillon 550.

In my case, it was late in the day - I was out of Russians and Specials - I had just a box of the subject rounds. The first two determined the drop - the third & fourth shot hit the 16" steel at 110 yd - the fifth one burst the gun - the sixth one was still intact, just squished it's case... I pulled the lead out easily (See photo.). I was blessed - a nick in my safety glass lens and a bloody small spot on my bare left arm were all I had to show for the experience. I found everything but the subject round's primer and a sight screw. It produced no recoil and only a muffled 'Boomff' followed by tinkle tinkle as the parts landed. I had instantly destroyed a $530 revolver only ~1.5 yr old - and which had launched only ~6-7 k rounds - only a few real Magnums - all made on that 550..



I called S&W. When asked, I told them it had probably shot it's only commercial rounds at their factory. Be honest with them. They sent a pre-paid label - and called me with their findings. The gun was dirty - the big bullet didn't exit fast enough for the fast burning Titegroup and a pressure spike occured, bursting the cylinder and the topstrap. The barrel was fine - and returned to me. The metal was tested - and found not to be a problem. They called me back - said they couldn't replace it - but I was a good customer. They subbed a standard production 4" 629-6 - when one came off the line in two days - for my MG - I was elated - the charge, with overnite s/h, was < half what I had paid for that new MG. The dealer didn't even charge me a xfr fee! I made out - honesty pays. Hodgdon's said that 6.2gr Titegroup behind a stuck bullet would have burst a Ruger, too.

Speaking of burst revolvers, S&W's burst upwards - Rugers go outwards and back.

Stainz

Addendum: As it should, such a catstrophe gives one pause for concern. Certainly, existing homebrew ammo is then all suspect. I dissected over 350 such loads - all fine. Of course, it only takes one. I attempted to make double loads - with no primer for safety. As I said, there was no way over 10.2 gr was going in a .44 Magnum case with that long and deep seating bullet without compression. The OP had something else going on - perhaps a high seated primer - to set off that adjacent round. He was indeed fortunate not to be hurt. Let's all be careful with our reloading - double check our powder drop settings... and always shoot the long cased rounds before the short cased ones... I knew better...