In practical terms, I've only even been compelled to shoot rapid fire in two kinds of situations; National Match Highpower, and Firefight Meeting Engagements in Vietnam. Surprisingly, I used the same firearm (mostly) in both, the M14/M1a.
Weight, recoil, and heat are the main considerations. The weight affects supporting muscles and framework, the mass affects recoil, and the heat affects accuracy (often permanently for that rifle) as it becomes extreme.
For unsupported shooting, lighter weight/mass helps. Shooting unsupported is in no small part a matter of confidence. We acquaint ourselves with the concept of the '
Wobble Zone', and then practice to make our own wobble zone smaller. Mostly, It's about relaxing and accepting the reality.
Rapid fire is not a big part of my training regimen. The only part of it that helps me is that it allows to speed up my recovery from recoil to back on target. Otherwise, I don't really foresee how rapid fire proficiency is going to prepare me for any real world application; and it can also accelerate bore wear.
Contrarily, it's really just a better way to waste ammunition faster, or as LowLight says, you can't miss fast enough to (insert desired outcome here).
I would only employ a heavy barrel in a supported shooting application, and I downplay the concept of a heat sink. While it's hot, the bigger thermal mass takes longer to cool, and all that heat is in there working away at the heat treating/barrel stress relationship.
In more practical terms, you wait longer before the barrel can accept more heat again. Folks rush that and the latent heat in the bore can end up burning up bore throats as they rush the cool down and return to shooting too early.
My heavy barrel rifles are Range Queens, and I bring several so I can shoot some more without having to wait interminably.
My field rifles are lightweight, with my antiquated Model 70 30-06 being the best example. I would never consider it for a firefight, but it did win me a 4th in the 1997 NJ State Sniper Championships by shooting at a reasonable firing cadence. I also know I can carry a rifle like that all day hunting deer.
Practical wisdom often turns out to be pleasing, but wrong.
I will tell you very simply that if your physical debility can be aggravated by recoil, you are doing yourself no favor by ignoring/hedging your medical prohibitions. If it's something your really like doing, hold off until you're certain you can continue it for the remainder of your life. It's worth the wait. Besides, that's why they make 22lr's
Greg
