avoiding double charges

I blew the top strap off a revolver yesterday. It was one of those aluminum/scandium/titanium jobs. I saw the hole on the target from the shot before and there is no barrel obstruction. The ejector rod was shot out and landed about 15' to the right. I never found the cylinder or the top strap. The load was a 158 gr. Berry's plated cast HP over 6 grains of BE-86 at 1.480" OAL in a new Starline .38 Special case. This is on the upper end of .38 Special +P, but the gun is .357 magnum. The revolver in question was problematic. It had broken twice before and each time went back to S&W to be fixed. They replaced the cylinder and crane the first time. The sear spring and the hand the second time, besides adjusting it. The gun had also cracked some nice cocobolo wood grips under recoil. I definitely wasn't getting along with it. Nevertheless, I have to consider the possibility that I fed it a double-charge.

I had loaded 126 cartridges the same day. I weighed the remaining half of them and found they are all within 0.1 grain (complete cartridge weight). I'm using a Lee ABLP with an Auto Drum Powder Measure. It's pretty hard to get a double-charge without trying. Nevertheless, I frequently observe the powder level in the case before placing a bullet, but yesterday I did not look at every one. The press has not been disturbed since I loaded it, and everything is working as expected and the measure is dropping the correct mass of powder.

I'm thinking about ways to avoid this:

* go back to loading powder off the press and checking every load in a loading block

* visually inspect every load on the progressive press before placing a bullet - while this is sensible, it is more prone to failure than observing a batch of cases at a time

* weigh every cartridge after loading

* use a powder that fills the case (can't get a double-charge of H110 in there)

* Use a Dillon Powder Check

I decap, clean, and prime the cases off the press. Because the ABLP is somewhat flimsy, I think I'm determined to change to resizing separately. The press will operate more smoothly during critical operations if I'm not resizing at the same time. I have a carbide resizing die and I can easily resize the same operation I decap prior to cleaning. Besides making the press run smoother, it would free up a station for a powder check, though I've not determined that is the solution.

What do you do to make absolutely certain you never double-load a cartridge?

To answer a few questions asked:
The press is a Lee Auto Breech Lock Pro progressive press. It auto-indexes.

I am certain it wasn't a squib load, because I observed the hole in the paper from the previous round. The barrel was clear.

It could have been a timing issue. I had just received the gun back from S&W after I sent it to them because it was sometimes failing to advance the cylinder and was striking primers way off center since the previous time I sent it to them and they changed the cylinder. They changed the hand. Now, of all the cases I shot, the primers are struck on center. But I don't have the case that blew it. I searched for almost an hour. It's out there somewhere in the brush or grass. I saw when it fired it ejected stuff both to the left and to the right. I only found the rod to the right which is what I think nicked my trigger finger just above the middle knuckle.

I also notice the trigger is jammed in the rearward position. It didn't reset, but that may be because the cylinder release has moved forward. I see a lot of orange dust in the forcing cone. I suppose it is copper from the plated soft-cast bullet. I also see a concentric line from the 9 o'clock to 11 o'clock position.
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I think I'm going to get a lock-out die. It looks like a simple solution to help me make sure I do my part right.

Yes. I have one of these "Brightech LightView PRO LED Magnifying Clamp Lamp" on my bench/stand. The magnifier is good for looking at things up close, but the light by itself works good to see inside cases on the press. But when you're loading hundreds of cases, it takes unbroken discipline to check each case one at a time. I'm not making excuses, but there is a chance that I won't look that one time out of hundreds or thousands and that's all it takes.

With the Lee ABLP and Auto Drum Powder measure you can double-short-stroke. I use that feature all the time to set the powder measure for example. I short-stroke it, pull the case and measure many times until it throws correctly. Same thing with bullet seating depth. Short-stroke, pull the cartridge and check it with the calipers. But once it's setup, there is no reason to short-stroke it and I think I'd have to be pretty careless to bumble that way.

I remember that reloading session quite well. I had one jam, but it was when I was using same-weight TMJ bullets that I use in a longer-barreled revolver that would exceed maximum velocity for plated cast bullets. The powder-through die was not flaring the case mouth enough. I tend to set it to a minimum to reduce wear on brass. I crushed a case with a misaligned bullet during seating. I cleared it and turned my powder-through die down two more complete turns. After I started up again, the case mouths were taking bullets nicely. But that happened when I was using TMJ's and there's no doubt I was shooting the cast hollowpoints that were all loaded well after the case mouth flare adjustment was made. I had closed the case of TMJ and opened a different MTM case of the plated-HP and was half way through it when the snub nose revolver failed.

I've looked at the Hornady Powder Cop and the RCBS Lockout die. I like the Lockout die for now, but I'm also thinking about a couple other solutions.

* Swearing off aluminum revolvers, which I had pretty much done after the first two times it broke. But recognize steel guns won't survive if I make a mistake.
* Simplifying my recipes to only bulky powders. The only reason I wasn't using H110 for everything is because minimum loads of it produced too much recoil with that little ultralight revolver. Well, that problem is solved. I've only got heavyweights left. I've also got some IMR4227 which is another nice powder that fills cases and while it doesn't produce as much velocity as H110, it's more than enough out of the longer barrels I've got left.
* You can bet I'll be looking at every powder charge for a while. Not miss a single one for the rest of my life? I don't want to bet my fingers on it. I'll probably use the lockout die where it's appropriate. For rifle (lockout die won't work), besides everything else I can do (powder cop maybe), I think I'll weigh every finished cartridge. I don't use range-pickups but only brass I buy new all the same headstamp. I had something like 50 cartridges leftover from yesterday and they were all within 0.1 grain. A double-charge or squib would be obvious.