Ok i think im a little confused plz help me out.       I just got my ta31f and its mounted on top of my SIR with a Ta51 mount and i have not yet shot it,juss looking through it to get used to the BAC but When i aim at the doorknob a couple feet away with 2 eyes open i can see the Reticle pointed at the door knob(non magnified) but when it switches over to the magnified eye or when i close my left eye the reticle moved slightly to the left.
  Is this normal?Where will the bullet actually hit?will it actually hit where the unmagnified reticle is or when it is magnfied.

Bear with me cuz this is the first time im using a scope. Need explanation and tips plz

Thnx-

100% normal and this is one of the side effects of BAC. Its called PHORIA and it is worse for some people than others. We talk about this somewhat regularly here. Not constantly, but it comes up pretty consistent. The bullet will actually strike where the magnified image shows it providing you have it zeroed properly.

For the most part, the majority of shooters just learn to deal with and compensate for the relatively small variance between the magnified POI and the BAC POI. As for me, I figure if I am briskly cruising around in CQB using the BAC, Im aiming in the general area of the body and the small difference caused by phoria will never be enough to cause a problem. If I am having to take a more precise shot where shot placement is crucial, it is very likely that I will be aiming in (even if it is quickly) to take the shot. In this case I shoulf have the opportunity to use the magnified image and make the more precise shot.

"It all comes out in the wash..." is how I feel about phoria.

Great explanation new-arguy.Thank you

Actually, I'm going to nitpick at new_arguy's otherwise informative post just to clarify a small; but relevant detail.

Phoria is a medical condition where the muscles that align and move the eyes have weakened and your eyes no longer align or track perfectly. A majority of people have some phoria and it can become more prominent as you get older.

Even if you have zero phoria and perfect eyesight, you will still see the dot shift you talked about between magnified and unmagnified views. It is just a natural result of looking at anything from two different angles (left eye and right eye). However, the shift will be pretty minimal (less than 10% of the field of view for that scope).

If you DO have phoria, you will see a greater shift depending on how bad your phoria is.

I just wanted to make it clear that even if you have zero phoria, you are still going to see "dot shift" like you described; but for most of us (even those with slight phoria) it isn't a problem.

Thanks for the clarification. I dont know for sure, but I think that Trijicon calls this difference in POA/POI for their BAC scopes phoria. I may be mistaken, but thats what I think. If that is in fact the case, we'd call it phoria regardless of the shooters eye condition.

I shoot right handed but I'm left eye dominant.  Does shooting with your non-dominant (submissive? [:)]) eye cause a problem with an ACOG? ...is the phoria increased?

I haven't seen any change in the amount the dot shifts when using my weak eye and I doubt you would unless you did have some phoria (the medical condition, not the phrase as used here). In that case, you would probably see a difference since the whole issue is that your eyes don't align the same.

The major issue I've seen using my weak eye is that the switch from unmagnified (BAC mode) to maginified view takes a lot longer initially. It is almost like your brain is confused and can't decide which view it wants to use. You can overcome this pretty easily with practice though. Your brain just has to get used to it.

If your phoria free, you can also be experiencing what is known as parallaxing.

Your eyes were designed a few inches apart so that they actually see slightly different perspectives, which after your brain processes the signal, give you stereoscopic vision.  When you switch from using both eyes to just one, you get a different sight picture (which can be magnified by using a 4x scope).

Put your left hand up close to your face so your thumb is pointing your nose.  Open your right then left eye alternately and you'll see opposite sides of your hands.  Open both eyes and you'll see a blended image of both sides of your hand.

I would trust the scope up close.  But I don't think, like new-arguy said, that if something is a close to you as your doorknob it's going to make a difference.