Mosin Nagant trigger modification ?

[donws2]

Hey guys,

I saw this trigger modification kit on evilbay and got to thinking it would be an easy home tinker mod.
Removed link

Anyone try this and how did it work out for you? The reason I ask is I really like the triggers in my Finish MN's but the ones in my Russian WWII rifles are so poor compaired to the Fin's. I'm looking for a SAFE, and that's key, way to get a better trigger pull with out doing any permanent part mods. Thanks for taking the time to read my question and looking forward to your thoughts.
Donald

 

[BasraBoy]

Re: Mosin Nagant trigger modification ?

Don, not sure what the one in the Ebay link is that you posted as the item seems to have been removed?

My smith has just finished restoring/converting a Mosin to be scoped clone.

He changed the trigger out for a Timney that has a safety. You can read his notes/thoughts here:

http://www.thamesvalleyguns.co.uk/

and scroll down the Armourer's Notes on the left and click on the "Building a Mosin Sniper" link (No.20 in the list).

Only real problem seems to be the amount of wood he had to remove to get the Timney to fit...but he's very happy with the results.

We don't see that many Finnish M39's over here, but I've got one coming over....will be interested to compare the diffrence between the Russian and Finnish triggers!

 

[ric44]

Re: Mosin Nagant trigger modification ?

Ive seen most of the mods both sold and free for the Mosin rifles. What has worked for me and doesnt cost a dime is to tweak (as in controlled bend) the sear trigger spring to overcome some of the tension, then use a very thin washer or o ring between said spring and the receiver. Polish the sear face and the bolt notch. Reassemble and tighten the sear screw and your done. In the case of using the o ring you can vary the tightness of the screw and get a somewhat adjustable pull weight. Your mileage may vary and always tweak and try as you go......you can go too light. Try at your own risk folks.

 

[donws2]

Re: Mosin Nagant trigger modification ?

maybe this will help. I saved some pictures from the ad.

 

[roggom]

Re: Mosin Nagant trigger modification ?

Don, if you want safe, then dont do that washer mod. All it does is reduce the sear contact area and makes your trigger break sooner/ less weight. You see in the pic, they added a slack spring, because when you move the sear up, you will get a loose floppy trigger (once it is cocked). If you really want a trigger mod, then go Huber or timney.

I am not going to lie, as I have done the mod with aluminum shims (pop cans), but later took it out because it is just an unsafe bubba upgrade.

Whatever you decide to do, make sure to do your cycle and drop tests.

 

[Joop]

Re: Mosin Nagant trigger modification ?

ric44 and roggom are both spot on. I avoid shimming the sear, as it just creates more problems, most of the time. I will typically do a slight bend and polish, as ric44 described. Depending on the parts (shapes of triggers, for example, can vary widely), you can get a quasi two stage pull, or a light, crisp single stage. The single stage type break is the one you want to watch out for, however. There's a fine line between a nice trigger and a dangerous one. The overall best options, from a functional standpoint, would be the aftermarket Huber or Timney, or a Finn M39 trigger. That would bar the rifle from some competitions, however, if that's your goal.

John

 

[donws2]

Re: Mosin Nagant trigger modification ?

Well I have to conceed the fact it's a bad idea. I pulled one of my rifle apart and pulled the trigger and sear out. There is no where near enough threads on the sear screw to hold the parts together if you add a thick shim. I think I'll keep my eyes open for Finish made trigger parts. The Fin's seem to have figured out how to to the job and to the trigger safe. Thanks for putting up with the questions.

 

[Wannashootit]

Re: Mosin Nagant trigger modification ?

Timney.
Adjustable, match grade trigger AND a real, "useable" safety.

 

[Joop]

Re: Mosin Nagant trigger modification ?

Don,

Just for the sake of discussion; IF you were to use a shim, it would not take much, at all to change the amount of sear engagement on the cocking piece. In the pics you posted above, that washer is at least two or three times too thick, in my opinion. If you were to add a shim that thick, it's not only likely that you would have to bend the sear upward, but I can almost guarantee that you would absolutely have to have that return spring. Not only to keep the trigger from rattling around, but to keep the bolt from pulling out when you cycled it, which is another result of this wonderful idea.

As for bending the sear, as a general rule, if you can see how much you've bent it, by looking at it, you've gone too far! It's usually a VERY subtle affair. Give it a try and see what you find. You will be able to improve the trigger pull and break without spending a dime and, if you test as you go, it can be done safely. Granted, it may not be the match grade trigger everybody would love to have, but it's a great improvement over what usually comes on the common refurb 91/30.

John

 

[donws2]

Re: Mosin Nagant trigger modification ?

Wanashootit, the idea was to do the trigger on the cheap. A timney would cost more than twice what I paid for some of the MN's I own and I have four rifles I want to improve. I could use the money for four timney triggers and buy four more rifles and have all the spares parts I need to do just about any mod that comes to mind. Plus as I understand it you have to hog out a shit load of wood inside the stock to make a timney fit. All in all not what I'm looking to get into but thanks for the idea.

Joop I've got a busted MN with a shot out barrel. I'll steel the sear from that one and play with stoning the contact surface to smooth up the pull first and then look at putting a bend in it to see if I can get a better pull. But I think the problem that would still arrise is the trigger just flopping arround before in contacts the sear. The idea of a trigger return spring may still be a vaid part to make and install. Anyway I have a couple weeks before all the PU parts arrive so I have plenty of time before I complete the three snipers. Thank for your help.
Donald

 

[Joop]

Re: Mosin Nagant trigger modification ?

Don,

Pictures are worth a thousand words (and in this case, probably even more, if you read Russian!). These are from a Russian manual.

You should be able to bend the sear spring slightly, so that it doesn't case any "flop". To do this, try to make the bend occur more towards the end with the sear on it, rather than in the middle or at the flat with the hole in it. This way, you're not pulling it down away from the trigger, before the contact point with the trigger. I hope that makes sense. Once you get everything apart and your eyeballs on all the pieces, you'll start to see how all the angles work, etc.

John

 

[donws2]

Re: Mosin Nagant trigger modification ?

Thanks Joop, Those are great. I'll use a free translator to figure out what the instructions are. What soviet manual are these from. I may need to find a copy, even if it's a reprint for reference.

Donald

 

[Joop]

Re: Mosin Nagant trigger modification ?

Don,

Most of the info I've picked up on the web, including the diagrams. There is a translated sniper manual/handbook floating around that was done for the US Army, if I recall. Also, there are a couple of books regarding Soviet sniper/target rifles that have the same/similar info. I don't recall specifically what came from where, or the titles. I will try to look them up and can PM you the info when I find it.

John

 

[Clark]

Re: Mosin Nagant trigger modification ?

There is a lot of information and products for MN triggers that is bogus.

The pics I was posting 10 years ago about shimming the sear is not a good idea. It reduces sear - cocking piece engagement and is unsafe.

The pics I was posting 10 years ago about thinning the sear is not reliable. The sear can break.

The $80 Hubber after marked trigger has no effect.

90% of the youtube videos on how to improve MN triggers are ineffective.

Almost all the force needed to pull the trigger is driven by sear spring force.
Not by sear mating angle or polish. Not by cocking piece angle or polish. Not by firing pin spring force.
I have measured the effect of all these and they are down in the noise.

This is a graph of typical MN triggers I am modifying.
The way to understand it is Hooke's law:
http://en.wikipedia.org/wiki/Hooke's_law

In the graph we can see an 18 pound trigger [area on the right].
In the graph we can see a 5 pound trigger with full sear- cocking piece engagement. [ on the left]

<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/DPn8IdNJ_SE"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/DPn8IdNJ_SE" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>

In the into to that video I wrote:

<span style="font-style: italic">There were 8 variables studied:
a) firing pin spring force
b) cocking piece to sear fit geometry
c) cocking piece to sear friction
d) sear spring force
e) trigger to sear fit geometry
f) trigger to sear friction
g) sear to cocking piece take up

The original sear spring force was much more important than the other variables combined.
Much effort was wasted before that was discovered.

Improving the trigger is tested with 4 triggers, 4 sears, and 5 bolts.
That is 80 set ups tested for trigger pull, ranging from 4 pounds to 12 pounds.
Then improvements are made with 400 grit wet and dry paper.
Up to 5000 grit is tried but no improvements are found.
The answer it that MN trigger pull is dominated by sear spring force pre set.

An orderly process is developed for resetting the sear spring.

Warning:
Some force should remain to keep the relaxed sear pressing against the bottom of the receiver, for full sear engagement. It need not be the 12 pounds sometimes seen with MN sears, but I would like at least 1 pound of initial sear force, so the safeness of the trigger is not compromised.
If you want to bend the sear so far that does not even touch the receiver and it has limited engagement with the cocking piece, and 1 pound of trigger pull, that is your biz, but I would not hunt with that.</span>

 

[donws2]

Re: Mosin Nagant trigger modification ?

Thanks Joob. I look forward to see what you find out.

Clark I believe the Fin's had descovered basicly the same thing you just posted.
I pulled the trigger on one issue Izhevsk 91/30 and one Fin captured Izhevsk 91/30. There are clear differences in both the trigger and sear. The sear however really was put through a ringer by the Fins. The Fin sear still makes contact with the receiver but as you can see in the pictures I took it is bent quite a bit away from the issue sear and looks much more like the one in Joops picture above.
Triggers

 

[donws2]

Re: Mosin Nagant trigger modification ?

sears

 

[Wannashootit]

Re: Mosin Nagant trigger modification ?

I cringe every time I see posts with total amateurs- not even "garage gunsmiths"- modifying sears. Especially on a rifle whose safety is so difficult to use that most- don't.

The sear spring/trigger mechanism on the Mosin is so crude that I would never consider reducing sear engagement- and your tests seem to bear that out.

The Mosin Nagant trigger is a pig, period. You can put as much lipstick on it as you want, it's still a pig.

Don, while I note your comment, I understand it no more than those that say "Why would I put a $500 optic on a $100 rifle?"

Well, I have a $500 optic on mine, and a Timney, and the justification has absolutely nothing to do with what the rifle cost- rather, the investment was based on it's ability to shoot.
The rifle can hold minute of angle or less with handloads, so there's no reason to not make the same type of investment in it as our Remington 700's and Savages...

I see the topic of "modifying"- let's call it bending- the sears on Mosins come up all the time on various forums, and I find it seems to be taken a bit too casually. I just pray that one day I don't come across a thread regarding an "accident" that's just waiting to happen. Just my $.02.

 

[donws2]

Re: Mosin Nagant trigger modification ?

Whannashotit I own three SN3's and a SN9 by US optics.
I own two Night Force Bench rest and two NXS scopes.
I have Jard, Canjar and Timneys triggers in several guns.
I own Three GAP Rifles.
I own seven 40X rifles.
One rifle by Bruce Behr and several other custom rifles and pistols.
I restore/rebuild Nation Match M1 Garands and M1A's as a source of side income for a local gun shop.
I was trained by the US Army Reserves at Camp Robison near Little Rock, AR to build and maintain NM M14's for the Georgia National Guard in the late 80's.
I've adjusted the triggers on hundreds of Garand and M14 rifles as well as Remington, Winchester/FN, Kimbers, Sako's and to many other rifles to mention. I do not adjust AR triggers as they are only surfaced hardened and it's an unsafe thing to do if to much surface metal is removed. There are a couple dozen Hide members here that shoot rifles I've tuned for them and so far No One has complain or stated the work was subpar.
I think I can handle the single lever system of a Mosin 91/30 with proper instructions.
But I do not need to reinvent the wheel if someone else has done all the leg work so I've asked for people that have had firsthand experience on the Mosin to comment on what works and what does not.
If you bothered to read my first post the idea was not to bend anything as spring steel weakens if bent to the point that it does not return to it original shape after it's been through heat treatment. It well maybe the Fin's annealed the sear and bent them to the shape they wanted and then reheat treated. I'm not going to go to that much trouble. As I said I'll play a little bit with the extra sear I have and keep a eye out for real Finish made trigger parts. I've already emailed a guy in Finland that had the M39 trigger parts for sale on another board and with luck he may still have some.

 

[donws2]

Re: Mosin Nagant trigger modification ?

Clark just watched your video. Very interesting. After you made your adjustment to the sear did you try other triggers with the same sear to see if there was any improvement by carefull sellection of parts? Just curious.
As i wrote above the sear from the Finish capture Izhevsk has a compound bend like the picture Joop posted. I did not state that it looks like the Fin's thined the sear quite allot. Both on the upper and lower surface the Fin's removed some matterial. I'm sure this was done to make the sear spring force weaker. Have you looked at this as a posible way to improve the pull force. I could see several problems with this myself with the most obvious being the sear is to weak and it breaks or folds up. It would be great to have access to the technical data the Fin's developed for the different models of these rifles. They figured out how to make a winning 300 meter gun out of these in the 1920's Olympics. They must have put allot of work into those gun alone.

 

[Clark]

Re: Mosin Nagant trigger modification ?

Don is SC.

I was swapping all the parts around.
There were 4 sears.

<span style="font-style: italic">av Sear 1..8.4
av Sear 2.. 5.25
av Sear 3.. 6.175
av Sear 4.. 6.075
Sear spread 3.15 pounds</span>

Then I bent the sears.
I think the last one I bent was for the camera.
I don't think I did any more swapping after bending.

What killed me after a week was that if I measured the trigger force to move the sear back to where the trigger would normally release, the force was equal to the force to make the trigger release. Granted there is some sear - trigger friction but that turned out to be small.

I could have saved a week if Obi-Wan Kenobi's ghost had whispered to me, "Bend the sear, Clark, bend the sear."

 

[Wannashootit]

Re: Mosin Nagant trigger modification ?

Don,

You misinterpreted my post.
Nowhere did I claim to know YOUR level of knowledge and expertise in doing trigger jobs, or any other smithing skills.

I was commenting, in general, about the fact that I see this topic come up on forums very frequently, and that- IMO- it gets tossed about quite casually; and I've read posts from some guys doing trigger mods that don't seem to have the knowledge to mount a scope.

My only comment to you, in particular, concerned your statement that seemed to tie the "sense" of doing somewhat costly upgrades to what is a "cheap" rifle. I was only saying that I, make that judgement based on whether the rifle shoots, not what it cost me.

Hope this clears it up, was not making a personal attack, or judgement of any kind.

 

[Clark]

Re: Mosin Nagant trigger modification ?

When most people talk about trigger jobs, they talk about:
1) take up
2) force to release
3) over travel

Unless it is a target trigger, I leave the first and last alone.

In the case of the Mosin Nagant, I think there are two prudent ways to go:
1) Bend the sear to reduce the force to release is as low as possible and still have consistent sear - cocking piece full engagement. This should result in ~ 2.5 pounds force to release.
2) Pay $100 and get a Timney with a built in safety.
Adjust per my drawing to 1.5 pounds force to release.

My 26 second video about that trigger.
<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/iSmvBGYFUK4"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/iSmvBGYFUK4" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>

 

[Wannashootit]

Re: Mosin Nagant trigger modification ?

THANKS!

Timney provides NO instructions on adjusting pull weight, even though it is advertised as "adjustable"!!!

Going to work on mine tonight

 

[JL]

Re: Mosin Nagant trigger modification ?

Those mods work, have done it with several rifles.
Bending spring by tapping is safe method- you can always come back if trigger starts to brake too easily.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Joop</div><div class="ubbcode-body">Don,

Pictures are worth a thousand words (and in this case, probably even more, if you read Russian!). These are from a Russian manual.

You should be able to bend the sear spring slightly, so that it doesn't case any "flop". To do this, try to make the bend occur more towards the end with the sear on it, rather than in the middle or at the flat with the hole in it. This way, you're not pulling it down away from the trigger, before the contact point with the trigger. I hope that makes sense. Once you get everything apart and your eyeballs on all the pieces, you'll start to see how all the angles work, etc.

John

</div></div>

 

[MrBigg282]

Re: Mosin Nagant trigger modification ?

I've toyed with shims didnt like the idea the more i thought about it bending the sear did change it a little i'v stolen the set screw idea tried this and that and i have come to the conclusion the next 100 bucks i have squirreled away is going to buy me a timney. The most noticeable change to my trigger feel was building of the surface of the trigger that contacts the sear with weld and filing it back until the sear barely set flat against the receiver which eliminated a fair amount of the long creepy but the geometry of the trigger is poor and i'v given up hope of saving it