Am I holding on too tight

[Duey]

I
Would say try taking the shot after taking a couple of steadying breaths and then hold for no more than 2-3 seconds, actually taking the shot on the held breath stage
Any longer than 2-3 seconds and you will get slight shakes as the body hunts for oxygen

Surely better to breathe twice, then shoot during the 2 second natural pause between breathing out and breathing in again.

Thats the way I was taught.

That was what I was explaining! Obviously badly

[22short]

I don't know if it works the same in rifle shooting, but with Pistol shooters the advice was deep breath in then exhale about half, then you have a maximum of 20 seconds to fire before the shakes come, the optimum being around 10-12 seconds. As for the heartbeat throwing you off, I now suffer that whereas never before so it is probably a health or fitness thing.

[bsctiny]

I was taught to bring right leg up 1/4 to 1/2 way up.
To take aim and at same time take reasonably sized breathes,
And to exhale half a breath and take shot,then when shot has
struck target to exhale.I was taught this in the army cadets
by a police fire arms officer on Lee Enfields then in the regular army
on the smg.I still follow this training when using my air rifle.

[Mattnall]

The only trouble with holding a half breath is getting it exactly the same each time. Consistency is the key here.
Letting a relaxed exhale go until the natural pause is more consistent.

[bradaz11]