Dan, I have a Husky M38 dated 1946 whose action was a donor for a 6mm Remington project. I don't load it HOT but pressures are definitely well above milsurp 6.5x55.
I've put well over a thousand rounds through it and haven't seen any signs of stretching or cracking while checking it out magnetically.
The action has been modified with a kit that used to be available to #### on opening, rather than on closing.
It's one of my favorite rifles and has taken a lot of Coyotes and Marmots out of ranchers fields.
The sad reality of the 6.5 Swede case is that it just cries to be loaded to better performances. Same goes for the 7x57 and 8x57, 30-06 etc.
That being said, I've had a M38 receiver give a catastrophic failure with a max load of #44 powder (IMR3031), over standard CCI LR primers under 140 spbt bullets.
The top of the receiver blew off and stuck in the wall of the range.
When we checked that receiver, the reason it failed was obvious. When it was assembled, after its last FTR, it was over tightened and cracked.
I would have been able to detect this if I had bothered to magnaflux the receiver ring. Instead, I just trusted the proof tests done after the FTR.
#44 powder was a surplus Bofors made powder offered by Higginsons back in the day and the equivalent of IMR3031 but just 2% slower.
This powder went bad after a few years and my load may have contained powder that had broken down.
When this powder was used, after starting to turn, it usually caused rusting of the bore. That didn't happen when my rifle failed.
Any surplus rifle can give a negative surprise, when it's least expected.
I sold Potashminer a P14 barreled action a few years ago that was never assembled as a rifle. He went to take the barrel off it and the receiver cracked. Now, why this happened??? Was it cracked when I sold it? Not that I could see and I did check for that, before selling it.
Had it been tightened so much that it succumbed to the stress when PM unscrewed the barrel???
A few weeks ago, I had a lovely pristine 1935 Brazilian receiver crack on me when I went to pull the barrel from it, so I could drill and tap the receiver. If someone had told me this would happen on a 1935, made in Oberndorf, I would have been extremely skeptical.
This rifle still had grease in the bore and action, but someone had cut the barrel back and reprofiled the rear receiver bridge for a sporter back when these rifles could be had for $75, which was about a third of what a commercial action cost back then.
It broke my heart to see that lovely action destroyed, but I did manage to save the barrel, which now sits on another 98. Just need to get it to the range to see how it shoots.