At 6'8 and about 115kg I'm a pretty sizeable bloke but it really wasn't a big deal my 300 is suppressed if that matters ? I would do it again without hesitation, it's all in the technique. Wrap whatever arm you hold the fore with through the sling, then using the tension created by that to pull the but nice and firm into your shoulder and get a solid cheek weld (sounds complicated but it's easy as and having a rifle that fits you well certainly helps) you'll probably still wobble all over the place but it's much easier to steady the rifle with your front arm wrapped through the sling.
The recoil wasn't an issue at all, but I love my magnums and rarely shoot anything else.
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