I was installing a new factory HK91 semi trigger spring assembly in a semi trigger pack and when I functioned checked it the nose of the sear catches and hangs on the spring bends that are half way back towards the main body away from the roller. When I release the trigger I have to push the sear off the spring to let it up and reset.

Is there a difference in a factory semi pack with the sear or some other part of the trigger group that is different between a 91 and G3, minus the auto parts of course, that might cause the problem? It is a factory semi trigger spring and roller not the auto one. The aftermarket semi spring works fine as it does not have the offset bends half way back. I don't know anyone that has a factory semi to compare the parts.

What semi auto sear spring did you buy?
Is it this one?
https://www.robertrtg.com/store/pc/MATCH-SEMI-AUTO-SEAR-SPRING-FOR-HK-33p10.htm

That's the type I wound up putting in it. I bought this semi HK one years ago with the spacer in it. https://www.hkparts.net/shop/pc/German-Semi-Trigger-Pack-Or-Sear-Pack-Elbow-Spring-W-Roller-107p70.htm

That's actually a full auto that they bent to fit, I had one in my PTR that I bought years ago that I replaced as well. Is it the newest one you put in that has a problem?
If so the trigger box may have been modified out of spec. I have these in all my HK style guns: http://www.hkparts.net/shop/pc/Trigger-Box-US-Made-HK-Trigger-Pack-107p2384.htm

No it is a factory semi auto spring and not one bent. It does it in one of the new US made boxes and in the cut/altered one that came in the 51 when I got it. The two boxes matched up hole for hole when I checked them. You can see one in a pack in the enlarged pic at the link. https://www.hkparts.net/shop/pc/HK-German-SEMI-308-Trigger-Pack-Complete-107p217.htm   I am just curious is there some difference in a 91 and G3 part that would cause it to hang on the part. The boxes have the trigger stop in them. I may take it back apart and look at the trigger to see if it is make correctly where it hits the stop.

It should work fine, maybe take the whole thing apart and put it back together with a you tube video.

Thanks for the replies. I took it apart again and took more time comparing the new US made box I bought to the older converted one. I was wrong as to the holes being in the same place. The hole for the spring and spacer is higher on the new one and matches the location on drawings I found on the net. I pulled out some older drawings I found on the net in 06 and it shows the hole lower than the new drawings. I put the parts in the older box with the lower hole using the new factory semi spring, old spacer, and side shims and the trigger hits the stop before the sear touches the offset in the spring and does not get hung up.
Wish I had access to a factory one to see where the hole really goes and what the parts look like.

All of my "factory" ones are modified FA boxes, don't own a real HK semi, just clones so can't help you even with pics on that one. All I know is the US made boxes I linked to before
worked better than the modified FA and had no trouble at all fitting everything together. Good luck.