I cringe every time one of these threads are started. I'm no ballistics expert, nor do I profess to be. I have pressure tested extensively and experienced a double powder load twice. Thankfully I've never experienced a total double load. Anyone can make the mistake of discharging an SML. I've seen people shoot out a ramrod and also a loading funnel. You can never be too careful when loading, no matter who you are.
The beginning of the end for the MLII was an ex disgruntled employee of Savage who blew one up. Many of the blow-ups were due to accidental double loads and others were due to experimentation with non Savage approved loads. Folks were trying different combinations with no way of knowing what pressure they would produce. My extensive experience with QL and SML's allows me to accurately predict pressure within 1kpsi as proven by my pressure traces of said loads.
Rifle blow ups can happen. Try replacing your 72gr load of Reloder 22 in the old 300WM with 72gr of pistol powder. I promise it will not be a pleasant experience. That's why you should never have more than one powder open on the bench at any given time.
The first double powder load was a 50cal single shot with 72gr of N110 (2 loads of 36gr) under a 250gr saboted bullet. Quick Load estimates just under 80kpsi. Recoil was stiff but the barrel was NOT harmed in any way.
The other, I believe was a double powder load under a 300gr sabotless bullet. It was loaded by an elder in our SML group at a competition. my mistake was allowing another person to load the test load. I had my pressure test gun set up off the end of the firing line, testing loads on request. The barrel is 1.385" diameter straight with no taper to a length of 30". This is a super beefy barrel. When the load was fired, I knew it was not good. The pressure test equipment spiked to 113kpsi before the primer module ruptured which relieved some pressure. The barrel was bulged .005". Below is the actual trace that was recorded.
