Correct - However, in the case of a rundown - By Rule you DO award next base. And if forces other runners they move up also.

In the OP, For NSA one would have immediate dead ball. Award lead runner home. Trailing runner awarded base they would have obtained absent the obstruction.

Like I said, it stand to hinder the offended team and that is just outright wrong.

The OP doesn't indicate which base the runner was trying to reach when obstructed, just that the runner made it back to 3B safely. The runner may have been trying for home when obstructed and simply turned around. In this case, home would be the proper award to negate the obstruction.

I agree and noted such in my original response, but even then, by killing the play you deny the offended team from advancing, maybe even scoring runs on the play.

So he was wrong about NSA?

Thank you.

At the very least, I'm not alone in thinking there should have been more detail to the question.

What I found in the NSA rules is that NSA states that a runner being played on is awarded the base the runner would have attained had the OBS not occurred, same as ASA.

However, there is an exception for a runner obstructed during a rundown which will always be awarded the lead base of those the player was between during that rundown.

But again, IMO, killing the ball can penalize the offended team.

Play: bases loaded, less than two out. Ground ball to the pitcher, who throws to F3 for the out @ 1st base. F3 throws home and R1 gets caught in a rundown. After a couple of exchanges, as F2 is throwing toward 3B, R1 is OBS by F5 trying to get back to 3B. The ball gets by the player covering 3B, R1 gets up and scores as does R2 & R3 as the ball rolls all the way to the fence. Meanwhile, you are standing near the 3BL with hands in air ruling the ball dead (by rule). Now, instead of 3 runs, the offended team now only has one run and R2 & R3 are returned to the last base touched at the time of the OBS. Even if you ruled they were affected by the OBS, the best case scenario is that they are on 2nd & 3rd, but that still takes runs off the board that would have been scored had their rules been the same as most of the rest of the softball world.

In Fed, obstruction is a delayed dead ball. In ASA and/or NSA, is obstruction an immediate dead ball if a play is being made on a runner?

Not exactly - in ASA it's immediately dead if they tag out the obstructed runner - not just if a play is made on them.

So what is it in NSA. Have never used NSA rules so I am at a loss on this one. I'm see what Irish is saying where killing the ball too quickly can cause harm to the offended team.

NSA has an exception whereby they kill the ball (poor ball...) if obstruction occurs during a rundown.

As Mike said, it could potentially harm the offense by not allowing them to advance on a potential error. But also, how often do we see a trailing runner take an extra base (or two!) during a rundown - killing the ball early when the defense has not been able to tag out the runner even after obstructing them is not fair to the offense at all.

NSA kills the ball anytime the obstructed runner it the one on which the defense is making a play. The rundown exception just notes they will always get the lead base whether or not they would have attained it.

Now, my next question is, what defines a rundown?

True ... and good question. I think it's in the chapter about Hot Boxes in the section regarding Pickles.

IMO, a rundown begins when a fielder with possession of the ball causes a runner to stop: 1. advancing to the next base, or 2. returning the last attained base.

Which rule book?