Your bolded statement is non-sequitur. The compressive force to which the buffer is exposed is not uniquely dependent upon the carrier weight, and the rest of the “symptoms” he’s speculating either aren’t caused by excessive carrier speed at all, or aren’t ONLY caused by said.
Example: Dented brass on the case mouth has next to nothing to do with carrier speed - AR’s do not have a fixed ejector, it’s a spring ejector - so increasing carrier speed does not increase the ejection force. Dented case mouths are over strength ejectors pressing the case mouth against the extension during extraction. If that over strength ejector is over powering the extractor too early during the bolt stroke, it can fall limp in the action before it clears the port, causing a double feed or overbolt jam (really raunchy double feed), or it might cause a stovepipe if it does clear the port and leave the case head in the way of the closing bolt. But equally - an overstrength extractor can cause stovepipes as well, as the extractor doesn’t release the round readily to clear the bolt travel.
What you might be confusing here - dents in the case body below be shoulder where the round is bouncing off of the brass deflector (as it is designed to do) are typically an example of excessive carrier speed. The ejector is doing its job, as in flicking the case out of the port, but the carrier is pulling the case rearward so quickly, it cartwheels around and smashes its shoulder into the deflector. The faster the carrier, the faster the case is moving rearward, the faster it’s moving, the harder it hits the deflector. That’s a different symptom than dented mouths, squished by an overpowered ejector spring.
Not getting “rounds to cycle out of the magazine” might describe symptom of a multitude of operating issues; an undergassed or over sprung AR which is short stroking may not cycle rounds out of the magazine because it doesn’t open far enough to pick up the next round - leaving either an empty chamber, or a bolt-over jam. An overgassed or undermassed AR might outrun the mag and also leave the chamber empty or cause a bolt-over, but it also might just be an out of spec mag catch or out of spec mag leaving rounds too low in the receiver for pick up... Could be under powered ammo causing a short stroke, or a gas system leak, or excessive drag on the carrier, or over length buffer spring, or a plugged RE vent... or the OP may have said “it won’t feed from the mag,” generically, describing what is really a double feeding issue, described above, which has its own systemic solution.
So instead of speculating based on any particular source of a mechanical failure, I asked the OP to better define the symptoms, specifically why he thought he had a “bolt thrust” issue, other than feeling like the buffer was bouncing off of the RE (like it’s supposed to).
If his particular combination of symptoms are real, then a systematic troubleshooting of these symptoms will generally yield the singular solution.
But I rather expect this is nothing more than a thought experiment kind of akin to a hypochondriac perusing WebMD and determining they have EVERYTHING disease... AR’s with multiple concurrent/coincidental, independent failures do happen, but more often, it’s just one issue, and the troubleshooting path is short and sweet.
