Fit for purpose
If your chosen gun wasn’t made specifically for you, don’t panic. You’d be surprised at how much can be done to make a shotgun feel as if it was made to measure.
Stock dimensions—within reason— can be made to fit you (of course, if you’re a completely different shape and build to the previous owner, it may be tricky). Purdey craftsmen have altered a great many guns to fit new owners and even not such exclusive guns can be tweaked to make crucial differences. Length of stock can be increased, comb height raised and other changeable measurements made, including: l the length of pull (the distance between the trigger and centre of the butt) l the pitch (the angle of butt in relation to the top of the barrels) l the cast (the distance the stock is offset from the centre line of the barrels) l the drop (the distance from the top of the barrel to the comb and heel).
Ultimately, it’s all about hitting the target more often. Your measurements are unique to you and so your shotgun should be, too.