TargetTalk

We have an Avanti 887 which had the standard trigger mod performed by mechanic at a CMP camp, with the sear modification and the adjustment screw added. Recently, it started firing when the trigger guard is pressed, e.g. when picking the rifle up, resting a finger against the guard, etc, even with the trigger set at 1.5 pounds. Any ideas what might be loose, where a shim may be needed? Doesn't happen every time, just enough to be disconcerting.

I would check the trigger sear and the mating part on the striker/hammer. What you are looking for is if the angle of the sear has changed, making it easier to slip off the sear.

Also check to see that the trigger sear goes back into position smoothly. If the sear is hanging up, the striker could slip off the sear. Look for; too much THICK grease, binding, etc.

BTW, firing when it is not supposed to is not disconcerting, it is a safety issue.

Also keep in mind that the trigger assembly of the 887/888/, etc were not manufactured to go that low.

Not all of these rifles will allow you to do this. Whenever you are below about 1.8 lbs, it's even money whether you will get it down to 1.5.

Remember you MUST be able to pass the bump test too.... cocking the rifle and bumping the butt on the floor/table ... if it goes off, it is not safe.
Also a regular trigger pull gauge is not a valid method for determining pull weight .... it is lifting a weight off vertically

Rarely, if ever do I set an 887/888 below 2 lbs. If you are in a range where there is a temperature difference from where you set the trigger, even that can cause the trigger to go off.

If your shooter has their gun go off closing the bolt, it's too bad, so sad ... a miss and the RO should require the rifle to be pulled off the line.

That all said, make sure your shooter knows that they can put a trigger back to about 2 to 2-1/2 lbs .... leave enough room in your mod & polish so that even if they start backing that screw out it has some effect.

Root cause appeared to be the rear trigger assembly hold down screw not keeping the aft end of trigger assembly tightly shut.
I took the trigger unit apart and cleaned out the extensive quantity of factory vaseline/grease etc., Dirt wise it actually didn't look too bad for having 15000 rounds through it, I guess things stay cleaner when powder isn't being burnt. I had a tube of Krytox in my tool box, so I re-greased with a thin layer of that, we'll see if it likes it.
Re-assembled and still had issue when not in stock, noticed housing was opening slightly at rear when trigger guard pulled, screw which retains trigger assembly to stock also serves to squeeze aft end of trigger housing shut wasn't in place. I installed the screw, and depending upon torque/degree of engagement of threads, it may not hold aft end completely shut. A new screw that was nominally the same size seemed to hold the aft end shut better at a torque not so threatening to the aluminum casting, so I reassembled with that. Rifle seems to be working fine for the moment.