Sunday, June 3, 2007

Trigger job for your Mosin-Nagant 91/30

I picked up a 1943 Soviet Mosin-Nagant 91/30 recently for $89 at Big 5. The 91/30 (if you don't recognize it) is the second from the right in the following picture.

Nothing spectacular. It's a fine shooter that can group to 4" at 100yds. But the trigger was heavy and chunky. Naturally, this had to be remedied.

There are lots of websites discussing disassembly of the 91/30, so I won't repeat the recipes here -- consider it an exercise for the student. Here, we'll discuss only
  1. how to lighten the trigger, and
  2. smooth out the trigger pull.
After disassembling the rifle, and placing the action upside down on a table, you'll see the trigger and a leaf spring, screwed to the action, holding the trigger in place. This leaf spring serves two purposes. It provides trigger tension and is also the sear, which engages the bolt striker.

Unscrewing the screw holding the leaf spring in to the action, and pushing the trigger pivot pin,

frees the trigger and leaf spring from the action.

The tension in the leaf spring is what gives the trigger its weight. One can reduce tension to reduce the weight of the trigger. Simply put it in a vice between two pieces of hardwood

and bend, in the direction you want, to increase or decrease weight. Note, the nub sticking out is the sear, so be very careful not to damage it. Using very light HAND PRESSURE ONLY, bend the leaf spring in small increments, testing repeatedly. My trigger was too heavy. I wrapped a towel around the sear and pulled on the towel away from the sear to reduce tension in the spring.

You know you've achieved the right amount of tension when the spring lies flat when placed in the action and doesn't acquire any more tension when the screw holding it to the action is screwed tight.

The crunchiness/chunkiness in the trigger can be eliminated by gently stoning the surface of the sear and removing any burrs from the edges.

If you're feeling adventurous, and wish to reduce the length of pull (distance trigger has to move before the gun fires) of your trigger you can remove some material off the top face of the sear. This can be done with a file or with bench grinder. Be sure to take off small amounts of material at a time and retest often. After grinding/filing, apply the stone to the face of the sear and edges to give a nice smooth finish.


Weetabix said...

Does all the crunchiness come from the sear/bolt interface, or does some also come from where the trigger slides on the sear spring to push it down?

Does any come from the sides of the trigger rubbing on stuff as it rotates?

Does any come from the part of the bolt that the sear slides on ?

Felix Estrella said...

YMMV, but on Soviet guns parts are so loose that, at least on mine, I wouldn't worry about the trigger rubbing against its pivots.

The bolt side of the bolt-sear interface could be stoned too, if it needs it. Again, YMMV.

Weetabix said...

You had linked to the Brownell's stone in your GP100 post. Is it the M-Fine or the X-Fine?

Felix Estrella said...

Weetabix: I have one of each. The black is M-fine and the white is X-fine.

Kevin said...

I have a 91-30 also and I took the bolt apart to clean it. The instructions I read about that said the screw head at the back had to be flush, but when I did that the firing pin extended too far out the front. I adjusted it to where the firing pin is where it should be, but the screw head protrudes a wee bit. Is this a problem? I have not shot it since, and am a bit leery of doing so...

Felix Estrella said...

Hmmm. Firing pin protrusion would be a problem. Kevin: if you're local to me (Bay Area CA) drop me an email and perhaps I can take a look at your rifle.

Kevin said...

Alas! I live in SoCal... and I haven't had a whole lot of luck finding a decent gunsmith out this way...

Weetabix said...

Do you get any good out of bedding the action & floating the barrel?

How would you float it with that long old handguard on the top?

Felix Estrella said...

Hmmm. Never tried floating a Mosin barrel. May have to give it a shot. :-)

Weetabix said...

I think I'm ready to try this. You'd posted a link to some Brownell's stones in your GP100 post. I'm going to be ordering some other springs & stuff from Midway. Can you recommend any of their stones?

Here's a graceless link to the page I'm looking at:


P.S. Hope I did the link right.

Felix Estrella said...

I can't specifically recommend any of those stones, but I'd say ... generally, get the finest stone you can get and one grade rougher than that.

RenoRosso said...

I was pretty happy with this trigger mod, but might add in burnishing/polishing the sear spring where the trigger comes into contact with it. I noticed a lighter trigger pull after bending the spring, but also a little crunchiness about half way through the trigger pull. This crunchiness was gone after polishing the trigger/sear spring interface. Next step is to shorten the sear height, any recommendations for building a jig to use with a bench grinder?