How to tell - semi-auto is in battery?

[Jeffpatton00]

In the reloading forums there's much comment about adjusting headspace until the bolt closes with some slight resistance, to show that there's not excessive headspace. Of course, too much resistance (or failure to close) shows insufficient headspace. These indicators are great for a bolt gun with a bolt handle.

I reload for ARs, and I'm curious if there's a corollary for semi-autos. Normally the spring slams the BCG closed, so there's no way to tell how firm or slack the final thousandths of the closing is. If I remove the upper receiver and move the BCG forward with my finger, what indication should I look for to be certain the BCG is fully in battery with the locking lugs?

I don't know that I'd need to do this regularly, but after reading lots of suggestions about this for bolt guns, I'm curious if there's a corollary for semi-autos. thx,
Jeff

 

[jpd676]

Typically, for an AR you load to magazine length. I'm not sure how to measure what you are looking for but there are some people who shoot 1k competitions using single feed methoods in an AR. For me, that defeats the purpose of the AR entirely. I can get better accuracy from a bolt gun. I load to mag lenth and work on accuracy using different primers and powder charges or powders. Then I have other rounds ready to go should my first be a miss.