The buffer hammered the rear of the tube pretty hard to break it off. Did the buffer bumper look beat up? Make sure the correct buffer spring was used. If the spring was longer than the buffer when compressed upon itself it would not allow the 'bumper' to soften the impact.

I think the tube itself is a poor design though. Notice how thin the material is machined down at the point it cracked.

If you decide to run it suppressed I would personally=
Use a different type buffer tube and an adjustable gas block.
Or
Try a solid 9mm type buffer or fill the void in your buffer so the weights are stationary. This will slow extraction as much as possible and allow pressure to drop a bit more, it will also slow the carriers acceleration speed.
Try a heavier buffer spring. A heavy enough spring will stop the buffer from hammering the end of the tube. Heavy springs can be finicky though. Switching springs between suppressed and non suppressed may help.

I think mk13 is onto somrthing as well.

PSA is known for having too many varieties and it being a burden upon the buyer to read the fine print for what is specifically being sold and not assuming anything about what they are buying. In other words, did your pistol lower specifically say it was mil spec or that the receiver extension tube was mil spec, or even 7075 for that matter?

Not a PSA bash, but an old, and maybe not repeated as much nowadays because it's a bit of a given, issue.

The unholy trifecta (7.5", radical firearms upper, surpressed) coupled with a commercial spec receiver extension and/or 6061 aluminum and standard carbine buffer/spring combo was too much.

Measurement differences between mil spec and commercial tubes.

You can see in the photos that he has a pistol tube. His tube is not a typical pistol tube that is the same diameter for the length of the tube. His looks to be machined into a thin portion just before the threads and that was the area that broke. The combination of the short barrel and suppressor would probably be fine with a little tweaking to the gun and a regular pistol tube.
Maybe this will get PSA to rethink the machining on their pistol tubes? I think the broken area is machined to thin.

Yes, my bad, I am too used to using certain terms. In adddition to the dramatic step down in diameter just at the threads, do we know if this pistol receiver extension is 6061 or 7075? Or if the threads are commercial diameter or mil spec diameter? ETA: Or even way the threads were created?

“The unholy trifecta”

Out of all of my firearms (and I have quite a collection), to date, to only one have I given a name... my HK MR762, named Mr. Tickles.

But now, thanks to you, I have a second one named ‘The Unholy Trifecta’.  I love it - thanks Lightstriker!

LMAO!

Well, glad you're taking it in stride, as (for the record) it honestly wasn't meant as a derogatory remark against you.

I wasn’t offended at all.  I quite like it. For short, I’ve decided to call it King T.U.T.

Recoil will be higher than normal when the carrier is allowed to travel to the end of the buffer tube and bottom out swiftly against the end of the buffer tube.
In normal operation, the buffer just kisses the end of the tube.

Recoil was minimal, by the way.  Not sharp at all.

Any receiver extension that is going to break as a result of vigorous operation short of a kaboom is junk.