Regardless of sticking your elbow out or not...the buttstock still sits in the "pocket" of your shoulder. It doesn't move around depending if you stick your elbow out or not. Or at least it shouldn't.
Your head should be canted naturally (bit forward, bit to the side), not "flopped over" such that your neck feels strained. Your cheek should be on the stock, pretty much so your cheeck bone is sitting on the top of the stock (not quite but that's close). If your neck feels strained you're probably standing too "square" to your target, or your sights are set way too low for your physique. Raise the rifle a bit, turn in a bit more and you should notice that your head straightens up a bit.
Your weak shoulder should be forward of your strong shoulder...otherwise it's extremely hard to hold a rifle (your support arm just isn't that much longer
). Your feet will pretty much mirror what your shoulders are doing.
When you shoulder the rifle, if you find:
- that you have to reach excessively to support the rifle...try turning your body a bit more, and/or shorten the buttstock (either collapse the buttstock or get a shorter one).
- that your strong hand has to reach uncomfortably to take a grip (not strong grip, but natural hold) of the rifle and reach the trigger...collapse the buttstock or get a shorter one.
- that your neck is strained to see the sights that are "too low"...get risers to raise the sights, higher mounts to raise the sights, adjust the buttstock such that the entire rifle is raised higher.
NOTE:...for real steel you would not just simply place the "toe" of the buttplate higher on your shoulder as this would really start to hurt with rounds of significant recoil (or just snap your head back as the rifle slips off your shoulder)...you would position it such that there was as much contact between the buttplate and the "pocket" of your shoulder as possible. However, for airsoft...you can cheat like that...just don't do it with heavy recoiling real steel. Note the pic of the musket for an extreme example. The butt plate is going to go fully in the pocket...but the line of the sights is right up at eye level. There's a lot of "drop" to the buttstock of this rifle...had to do it since there was much of any sights on it.
The difference between sticking your elbow out or in is the shift/difference it makes to your center of gravity. If you keep your elbow in you have less "overhanging" weight, which adds to wobbling/sighting errors. Take a look at olympic/formal target shooters...their elbows are in as tight as they can get them to their core. They arch their backs to get the center of gravity over their hips...again minimizing and swaying.
That's formal shooting. For shooting moving targets where your body is rotating to lead the target a lot of people find it easier to "open up" a bit to gain a bit of balance/control when they're moving.
It's just a toy...but this figure actually has a very good shooting stance.
Shooting in sitting/kneeling is kind of similar to standing, but everyones body folds up a little different.
Shooting prone is totally different.
If you need help with it, it's best to do a bit of reading and then get someone at the next game to show you and correct your posture.
Note in the following pic how high the sights are on this rifle...lends itself to a very comfortable heads up position (his chin is almost on the stock pipe)...but there's a bit differential between the line of aim and the ballistic path of the bullet.
More "weight forward"...leaning a bit forward into the shot is good for real steel...it also rotates the buttstock up around the shoulder a bit to shorten the difference between the shoulder and eyeball position.
There's the "classic rifleman" stance.
