[size=2]For a first line of defense...

... any reasonable comparison or why should I keep 1200 rounds of I.M.I on hand.

Soliciting your opinions and comments[/size=2]

I'm not quite sure what the question is; I've used both rounds and they worked fine in a couple of different rifles.

As far as keeping 1200 rounds on hand I would think that the only reason for that is because you shot up the rest of your ammo stash practising at the range [;)]

... mostly asking because I hear a lot about SS109 Green Tip ammo and I'm not really sure why it costs twice as much as the next grade.

... inquiring minds wanna know

Basicly the greentip ss109 has a steel penetrator in the stip(mild steel core).It is suppose to have better penetration than the standard ammo but is not considered an ap round.

I read an article awhile back that explained how the SS109 bullet was made. Unfortunately I cannot remember the details but the bottom line was that when the steel core was inserted, it was not exactly centered in the bullet. This of course detracted from the accuracy.
I had a bag of the ss109 so I loaded some up & did a comparison against some 55gr FMJ in a 1in7 twist AR15. My initial thought was that the heavier bullet would be more accurate in that twist rate. But, the lighter bullet was more accurate. Now consider that it was a windy day & I was shooting prone on some very uncomfortable ground.
The ss109 had 2" groups & the 55gr. had 3/4" groups @ 100yds.
IMHO the ss109 has it's own uses but reliable accuracy is not one of them.

ColtShorty

GOA KABA COA JPFO SAF NRA

"I won't be wronged,  I won't be insulted
and I won't be laid a hand on. I don't do
these things to other people and I require
the same from them."