jmster: you are correct. Apologies for the disagreement.
No appoligies needed at all....I found this out the hard way when playing with the ILS system. While playing around I tried cutting off a coil or two off the short hammer spring to get the heavy lbs down, and found this caused the spring to be way underpowered, it's pretty short and stiff.
Can't one remove the key lock and circumvent the assorted problems it seems too cause.
Yep, you can actually put all regular GI parts in the MSH, add the retaining pin that regular gi mil-specs all have and the ILS models do not have. Most people just buy another MSH that does not have the extra hole there for the key lock cause it's looks better. As rbwillnj pointed out, mainspring cap is different as well with the ILS system. This ILS design needs a take down pin to take things apart, where the regular GI models already have a retaining pin in there that captures the cap full time.
I was thinking, if someone tried to lighten the trigger pull on this one, just ask what it was they did.
The stock short mainspring on the ILS system is at least 29 lbs...it hits hard. But if you shorten it very much at all to try to ease the trigger pull, there isn't enough length to hit hard enough.
For just a few bucks you could order an ED Brown pin and spring set, it has all the stock stuff that goes in a stock MSH, proper cap, 23 lbs spring, retaining pin, plus a bunch of other stuff. The 23 lbs hammer spring was enough to fire mine even with the light firing pin, although I have changed to a heavier FP since.
Or you could send it to SA...they have good customer service and will fix it. Not sure what the charge is if they can tell someone did a "trigger" job to it...but they are very nice people there.
Still wondering what they did to give you a trigger job.?