Ryan P.
Member
Since my other idea on tweaking the Mosin's safety in a different way than I had seen others try did not go as expected (A Different Mosin Safety Mod. Idea); it was a good learning experience that reached the desired end, just in a different way than expected... 
So I figured I would post a SUCCESS on my Mosin-Nagant hobby gunsmithing adventure.
Background: Mosin triggers suuuuuuuuck. I bet you knew that.
So the only gun I had previously to a few years ago was a Remington 870, so to me the feel of an 870 trigger is normal; I wanted to duplicate that on the Mosin as best I could.
Forgive me if I get a term technically wrong, but I figured a trigger has a few quantitative properties as I'll define them here;
play: amount of movement before trigger starts moving sear
creep: amount of movement to fully clear the sear and fire
pull: force necessary to accomplish firing
In stock form the play is large, the creep is long, and the pull is heavy!
I tried the common "fixes;
Shimming out the sear spring; this lowers the pull, creep about the same, but increases the play a lot.
Putting in a trigger return spring, creating the 2-stage trigger; this makes the play consistent, but leaves the creep and the pull unchanged.
Polishing all surfaces, even sear faces, very carefully; made the action smooth, but the play, creep, and pull were essentially unchanged (pull decreased very slightly).
The stock pull actually doesn't bother me; a Remington 870 trigger is "normal" to me, remember? So 5-6 lbs...whatever, fine...big, meaty WI country boy fingers...no problem. But that play and creep...HATED IT! Especially the creep...pull and pull and pull and...is thing thing broken? Will it ever go off? BANG! Sheesh.
So I liked the idea that the Finnish trigger has: move the contact point. THAT is the Mosin's trigger sin in my mind; that goofy curve that touches the sear spring has an ineffective slope to it.
So I graphed it in about 1000x scale so I could see what was going on;
Pinned it as it would be to pivot correctly, and played with generating some graphs of how the sear spring would move for a controlled trigger movement. See how the contact point slopes away as the trigger moves back?
After that, I determined the best path to improvement was adding a 1/16" SS Dowel across it as shown with the red circle.
Note how the stock point of contact for the sear spring remains unchanged (red line).
I bought a second trigger just in case this all didn't work, and then measured about 4x, jigged it all up flat and true, and then made a thin notch with a cut-off wheel, dropped the dowel in, and sealed it up with JB Weld.
Cleaned up the epoxy "flash" and polished everything back up with 600 grit sand paper.
Note how the contact point is now the furthest front edge; maximum sear displacement for trigger movement.
I actually ended up just a hair lower and further forward than planned. But it worked out better; now when the trigger assembly is installed, it puts just a hair of pre-load on the sear spring.
At the final assembly and dry fire testing;
Play is ZERO.
Creep is ~ 1/2 what it was.
Pull is basically unchanged...I might have shaved off 1-1.5 lbs, if I remember right.
But most importantly from the safety aspect, the amount of sear face contact is unchanged, the ratio of trigger movement to sear movement is now just accelerated.
I need to get out and live fire it still, but I am very happy with it as it stands now.
So I figured I would post a SUCCESS on my Mosin-Nagant hobby gunsmithing adventure.
Background: Mosin triggers suuuuuuuuck. I bet you knew that.
So the only gun I had previously to a few years ago was a Remington 870, so to me the feel of an 870 trigger is normal; I wanted to duplicate that on the Mosin as best I could.
Forgive me if I get a term technically wrong, but I figured a trigger has a few quantitative properties as I'll define them here;
play: amount of movement before trigger starts moving sear
creep: amount of movement to fully clear the sear and fire
pull: force necessary to accomplish firing
In stock form the play is large, the creep is long, and the pull is heavy!
I tried the common "fixes;
Shimming out the sear spring; this lowers the pull, creep about the same, but increases the play a lot.
Putting in a trigger return spring, creating the 2-stage trigger; this makes the play consistent, but leaves the creep and the pull unchanged.
Polishing all surfaces, even sear faces, very carefully; made the action smooth, but the play, creep, and pull were essentially unchanged (pull decreased very slightly).
The stock pull actually doesn't bother me; a Remington 870 trigger is "normal" to me, remember? So 5-6 lbs...whatever, fine...big, meaty WI country boy fingers...no problem. But that play and creep...HATED IT! Especially the creep...pull and pull and pull and...is thing thing broken? Will it ever go off? BANG! Sheesh.
So I liked the idea that the Finnish trigger has: move the contact point. THAT is the Mosin's trigger sin in my mind; that goofy curve that touches the sear spring has an ineffective slope to it.
So I graphed it in about 1000x scale so I could see what was going on;
Pinned it as it would be to pivot correctly, and played with generating some graphs of how the sear spring would move for a controlled trigger movement. See how the contact point slopes away as the trigger moves back?
After that, I determined the best path to improvement was adding a 1/16" SS Dowel across it as shown with the red circle.
Note how the stock point of contact for the sear spring remains unchanged (red line).
I bought a second trigger just in case this all didn't work,
and then measured about 4x, jigged it all up flat and true, and then made a thin notch with a cut-off wheel, dropped the dowel in, and sealed it up with JB Weld.
Cleaned up the epoxy "flash" and polished everything back up with 600 grit sand paper.
Note how the contact point is now the furthest front edge; maximum sear displacement for trigger movement.
I actually ended up just a hair lower and further forward than planned. But it worked out better; now when the trigger assembly is installed, it puts just a hair of pre-load on the sear spring.
At the final assembly and dry fire testing;
Play is ZERO.
Creep is ~ 1/2 what it was.
Pull is basically unchanged...I might have shaved off 1-1.5 lbs, if I remember right.
But most importantly from the safety aspect, the amount of sear face contact is unchanged, the ratio of trigger movement to sear movement is now just accelerated.
I need to get out and live fire it still, but I am very happy with it as it stands now.
