So I'll try to keep this short. I spent two hours trying to install a new Texas AK trigger in my Zastava PAP. I had already replaced the stock trigger with an Arsenal but still had trigger slap when firing. Rather than machine the original trigger to fix this or the Arsenal trigger, I decided to buy the Texas trigger "guaranteed to fix trigger slap". Well right off the bat I had trouble getting the hammer pin to seat flush. It would go in all but about 1/16 inch. I thought maybe I had a coil of the hammer spring pinched, interfering with the pin. I tried numerous times to figure out WTF the problem was.
After closer inspection of the hammer from TT, I noticed the counter sink machined into the hole for the hammer pin was not as deep as the Arsenal hammer. This is why the hammer pin would not seat flush against the outside of the receiver. It was bottoming out on the counter sunk shoulder of the TT hammer pin. Therefore I couldn't get the shepard's hook or pin retaining plate in place. Very frustrating to say the least. Now I'm not sure what to do with the Texas Trigger.

Why don't you contact them. Maybe they can help.

Bummer,  little work with a Dremel will fix it though.

I actually bought it from AK-builder.com. I will try contacting Texas Triggers tomorrow. I just started messing with it this evening. As long as it shoots without slap now I'm happy. I could always put it here for sale or I was wondering if it might fit my M77 AK in .308