6.5-300 Weatherby, 140gr ELD-X, & 63gr of IMR4350 v.BOOM [QuickLoad Anyone?]

[TSFineGuns]

I would love if someone could run this through QuickLoad and get back to me with the pressure!

My cousin picked up a left-handed Weatherby Mark V Backcountry 2.0 Ti Carbon from Sportsman's Warehouse some months ago. Paid a pretty penny for it too. He was coming to visit me a few months ago and I told him to bring a fired case with him so I could make him a Modified Case. He hadn't shot it yet, so he said he'd load one up and fire it before he came down.

He calls me the next morning and said he EF'd Up. He said he loaded a round to fireform it before he left to come down. Turns out it wasn't US869 in his powder hopper. The shot made a hell of a boom, and he couldn't open the bolt. Took it back to Sportsman's Warehouse to see if they could work on it. They couldn't get it open either. So my cousin asked them to send it back to Weatherby to have them look at it.

Weatherby's Response:

"Upon the initial inspection, the gunsmiths found that the rifle is unrepairable from the damage that was sustained. The gunsmith found that the lugs of the bolt and receiver are severely damaged. The chamber is damaged beyond repair and a crack was found in the mortise area of the stock. The rifle is no longer safe to use."

$3,800 mistake by leaving powder in his hopper and not having the hopper labeled with the powder type. I wanted to give him a hard time about it, but damn.

I'm beyond curious to know what sort of pressure that load had to do that much devastation to the rifle. If anyone could run that data, I would greatly appreciate it.

**And legit, this isn't me 'Asking for a Friend'. This was my cousin....lol

RIP

​

 

[Jager]

63.0 grains of either IMR-4350 or US869 behind a 140gr bullet is nowhere near the max chamber pressure for the 6.5-300 Weatherby. IMR-4350 would be very light. And US869 would be extraordinarily light.

If I had to guess, I'd speculate that it was US869 in that hopper, and that he experienced a rare phenomenon called Secondary Explosion Effect. Very light loads, slow powders, and large case capacities are the factors common to that phenomenon.

 

[TSFineGuns]

63.0 grains of either IMR-4350 or US869 behind a 140gr bullet is nowhere near the max chamber pressure for the 6.5-300 Weatherby. IMR-4350 would be very light. And US869 would be extraordinarily light.

If I had to guess, I'd speculate that it was US869 in that hopper, and that he experienced a rare phenomenon called Secondary Explosion Effect. Very light loads, slow powders, and large case capacities are the factors common to that phenomenon.

It was verified as IMR4350. He looked at his reloading logs and the last time it was used was when we loaded a few rounds of .250 Savage Ackley Improved. He never removed the powder from that session.

63gr is a light load in that case, but IMR4350 is way too fast of a powder in that case.

I've read a lot about reduced loads and the dangers of going too low, so that could be something too.

I just figured with IMR4350 in that caliber, it was way too fast and the pressure went through the roof.

 

[SeabeeKen]

well under 60,000 psi and about 77% case fill. I shot IMR3031 at 80% case fill in a 243 for years and never an issue. I cant see 4350 causing that. Are you positive it wasn't a different powder?

 

[TSFineGuns]

well under 60,000 psi and about 77% case fill. I shot IMR3031 at 80% case fill in a 243 for years and never an issue. I cant see 4350 causing that. Are you positive it wasn't a different powder?

Interesting. I will talk with him later today, but when I talked with him last night, he said he hadn't reloaded any rounds for his firearms since winter of 2022. I was up there this summer and we loaded some .250 Savage AI as I said. We used his powder dispenser, so that's the only powder that he thinks it could be now.

Unlabeled, is there really any way to verify that it was or was not IMR4350? I'm not aware of one?

 

[TrapperBR549]

Any possibility of another cause, such as barrel obstruction?

 

[Jager]

So he hasn't reloaded in two years... some kind of powder was left in his hopper all that time... and between his memory and whatever his handlload log says he thought it must be US 869. Or maybe IMR-4350.

With all due respect to your cousin, not exactly a very rigorous system there. I'm not sure "verified as IMR4350" applies.

IMR-4350 is slow enough that it has been known to cause S.E.E. (Secondary Explosion Effect) in certain circumstances. But I don't see that as very likely here. It would be making somewhere around 54K psi in your cousin's scenario. He'd have probably been okay.

US 869, on the other hand, is a much slower powder. 63 grains would be an extraordinarily awful load, producing something around 11-12K psi, with lots of unburned powder. S.E.E. is rare enough that ballistics labs have a hard time reproducing it at will. But your cousin's concoction, if it indeed was US 869, is probably the surest path to S.E.E. that I've ever heard of.

If it wasn't US 869, it was probably some kind of pistol powder.

 

[TSFineGuns]

So he hasn't reloaded in two years... some kind of powder was left in his hopper all that time... and between his memory and whatever his handlload log says he thought it must be US 869. Or maybe IMR-4350.

With all due respect to your cousin, not exactly a very rigorous system there. I'm not sure "verified as IMR4350" applies.

IMR-4350 is slow enough that it has been known to cause S.E.E. (Secondary Explosion Effect) in certain circumstances. But I don't see that as very likely here. It would be making somewhere around 54K psi in your cousin's scenario. He'd have probably been okay.

US 869, on the other hand, is a much slower powder. 63 grains would be an extraordinarily awful load, producing something around 11-12K psi, with lots of unburned powder. S.E.E. is rare enough that ballistics labs have a hard time reproducing it at will. But your cousin's concoction, if it indeed was US 869, is probably the surest path to S.E.E. that I've ever heard of.

If it wasn't US 869, it was probably some kind of pistol powder.

Just over a year, but nonetheless, leaving unlabeled powder in his hopper is not something he should have done. He's the polar opposite of me. I only take out what I'm using, and when done, I put it all away and clean off my bench so situations like this do not occur.

We can rule out pistol powder completely, as he only reloads for his hunting rifles.

So your money is on S.E.E.? I'm not familiar with that, but would that be able to do the damage to the rifle that Weatherby is stating?

 

[Jager]

So your money is on S.E.E.? I'm not familiar with that, but would that be able to do the damage to the rifle that Weatherby is stating?

Absolutely.

S.E.E., when it occurs, produces very high pressure excursions.

 

[TSFineGuns]

Absolutely.

S.E.E., when it occurs, produces very high pressure excursions.

Thanks for your input/ideas. Genuinely appreciate it!