Sleeve length and shoulder width considerations

[Newmexican]

I've been thinking about the relationship between the length of the sleeves and the width of the shoulder relative to determining a correct sleeve length on a new A2 yet to be ordered . For example, if I have a jacket that fits me well with respect to sleeve length with the following measurements:

Sleeve length = 26"

Shoulder width = 18"
If I take the sleeve length, double it (26×2) and add it to the shoulder width (26×2) + 18 = 70

Now, if I see an A2 for sale with the following measurements:

Sleeve length = 25.5"

Shoulder width = 19"
So (25.5×2)+19=70

Does this mean that the sleeve length would fit the same on both jackets?
If true, knowing this would be helpful in determining the correct sleeve length in jackets with different shoulder width. Nor sure if this is even a valid way of doing this.
Thanks for your comments and opinions.

 

[mulceber]

Generally yes, but the patterns of different contracts varied so widely that this doesn't make for an exact science. It'll probably fit, but I wouldn't expect it to fit in the same way.