Accurizing/Sporterizing a Mosin Nagant


July 17, 2012, 09:00 PM
I'd been wanting a laminate featherwieght thumbhole stock for my Mosin for some time. My ultimate goal is to add a scope and do some acurizing mods. Lighter trigger, float the barrel etc. So I ordered stock from Byods stocks, I really wanted something with the blue hues in in the wood, I think that looks really nice. Unfortunately they don't offer that for the mosin. So I ordered what I found to be the next most attractive which they refered to as the Jacaranda. They told me a 3-4 week back order, which was more than fair. But to my surprise I got a tracking number just 8 days later! If finally arrived it was much nicer than the one on the website. Fitting it took a about 30 min of filling a few spots, maybe a 0.001".
I have no dillusions of making a match grade DMR from this but im certain i can clean it up a bit. Its got a shinny bore with sharp riffling, it is counter bored so I have to chop some and recrown it. Its going to be a long and slow process with lots of trial and error. But thats half the fun. Ill post updates as i make progress. Once I get close I'l bedding the action. For now I simply free floated it, and improved the trigger. I use a combination of a single shim, a slight tweak of the spring and a bit of filing down the disconnector. Result: 3lbs pull, and 1/4" of travel.
After much research I decied to chop and recrown with an 11degree target crown. Initally I was only going to cut 2 inches off the barrel where the counter bored ended. Unfortunately the steady rest on my lathe only closed to 1.5" and buying a $70 crowning tool for a $100 rifle seemed extreme. Solution? Eleminate the need for the steady rest. Cut the barrel short enough I could work closely to the chuck to elemenate chatter.
After a few careful mesurments using a TIG rod down the barrle to the bolt face I determined that my barrel was 28.75", where I needed to clamp was right infront of the sight block so that left me 13" to work with...Good thing the barrel extends another 3" behind that! So for safey's sake I cut it at 17 1/4" with a band saw. Chucked her up in the lathe, and ran at about 58 RPM with a No3 Carbide cutting from the bore out to prevent a bur from forming on the I.D of the barrel. Once square cut I repoistioned the cutting tool to 11 degress and again cut from the center out, till I had a nice fat target crown. Then I cranked it up too 300 RPM and did some sanding, then up to 500 rpm for some polishing with machinst scotch brite. (the medium corse red stuff).
From there it was over to the mill to locate a new spot for the front sight to weld down to. Then because I'm no good with silver solder, it was TIG time! Next will be a complete reblue or maybe duracoat for the whole rifle. I'll post pics of the finished rifle after recoating. And of course preliminary range testing, before I move on to mounting a scope. I'll be sure to do a write up for that process to depending on which route I go.

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July 17, 2012, 09:03 PM
Adding a few more pics of the process.

July 17, 2012, 09:05 PM
this is the final assmebled version before recoating.

July 17, 2012, 09:40 PM
Be careful with that trigger, at three lbs on a mosin I bet if it is cocked and you drop it n the but it will be discharging - make sure it is not! if it isn't post detailed pictures on what mods you made. I had the same stock from Boyd's arrive yesterday but have not got around to fitting It yet.

July 17, 2012, 09:47 PM
Thanks for asking, now ofcourse nothing can simulate real world conditions like real world conditions, but the trigger passed the 4 direction rubber mallet test quiet a few times. In short I couldn't make it fail no matter what I tried. The reduction in pull pressure isn't from less contact, but rather the adjusted spring tension, the shim was to create the proper alingment of the disconnector with the new spring angle. As opposed to just using the shim to make minimal surface contact as is popular with most DIY jobs on mosin's.
Being it's a target rifle, (not going to be used outside the range) it won't be loaded besides pointing down range. A hair trigger is never a problem when your practicing your 4 basic rules of saftey.

July 17, 2012, 11:11 PM
How did you adjust the spring tensin on the sear?

July 17, 2012, 11:20 PM
by changing the angle of it in two places

July 18, 2012, 09:53 AM
what were the pivot points? after the sear, and after the mount screw point? Mind posting a picture of the finished Sear angle?

July 18, 2012, 04:20 PM
The pivot is right at the base, and the other right at the sear. I'll post a pic in later on when I get a chance to break her down again.

July 20, 2012, 08:40 PM
I think its cool. Did your trigger work out?

July 21, 2012, 12:15 AM
I won't get it to the range untill next weekend, unfortunately. I'll be sure to include a range report, and thanks. I'm hoping the work was worth it.

July 24, 2012, 10:51 PM
Okay, Disclaimer first.
Any improper modification to any firearm trigger may result in unintentional discharge and serious injury including death and property damage,criminal and civil liabilites.

Now, on to the technical disclaimer. These rifles have many different tolerances, as many parts were ground and finished by hand. The values I've included worked on THIS rifle and may not work on others safely, or may not work at all. This is included for educational purpose and I'm not advocating you do anything I do yourself.

July 24, 2012, 10:52 PM
More pics

July 25, 2012, 01:15 PM
This is the best info Thanks!!

July 25, 2012, 01:40 PM
I used a set of feeler guages to establish my shim thickness, and constantly checked my pull strenghth. I must've taken that trigger apart 100 times that day. Then I'd hold the gun in one hand and smack the sides of the recevier and the hilt with a rubber mallet and made sure that the trigger wouldn't slip.

July 25, 2012, 05:16 PM
In this thread from 2004 you can see I have a spacer underneath the rear of a sear.

I have since given up on that after making a lot of measurements.

These days I do a single bend on the sear or put in a Timney trigger.

I have worked on about a dozen Mosin Nagants.
In the 1960s, it was very well documented the ways of sporterizing Mausers.
But we are just now learning how to do Mosin Nagants.

Here is a 5 minute video about MN trigger jobs where I measure the effects of:
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
h) Hubber trigger
i) Timney trigger

Then I show how to bend the sear using a dial indicator and a force gauge.

July 25, 2012, 11:40 PM
Thanks for the contribution Clark. Hopefully this thread will become a comprehensive tool for those who are interested in these projects. I just don't have the drive to make videos. Once I start working I usally get to focused to think about even taking pics.

Alan LA
August 29, 2012, 04:38 PM
Nice job! I'm starting the same on my MN. I've installed a Timney trigger set at 2.5 lb. Next will be a Rock Solid scope mount. After I get the scope mounted, then I can REALLY see what the gun will do. If it lives up to it's potential, I'll get a Boyd's thumbhole stock and shorten the barrel to 22".

August 30, 2012, 10:27 AM
The last MN I built got ugly, the next one will be a hunter.

I have a video about making my own Mosin Nagant scope mounts.

You may be able to use the Advanced Technology mount instead of the Rock Solid.

August 31, 2012, 12:10 AM
Thanks for the kind words guys!
I just recently finished fabricating my own scope mount. I set it a little high so I can still use the open sights out to 200m. It was a bit more work than I anticipated, but the resulting mount is VERY solid.

August 31, 2012, 02:50 AM
Nice mods everyone. Clark thanks for the post and link / video. I was planning to shim the sear but you may have convinced me to bend instead. Any recommendations for bending without a dial gauge force meter or vice? Pliers and be careful bending just a tiny but at a time? Or without the gauges is it safer to shim?

Shadow 7D
September 1, 2012, 04:12 AM
Can someone post the Finn trigger blue prints (with translation please) they actually thinned and bent the sear slightly and adjusted the engagement angle of the sear.

Alan LA
February 18, 2013, 06:53 PM
Clark, will the ATI take the abuse the Rock Solid mount will? By abuse, I mean recoil.

February 19, 2013, 01:06 AM
Shadow7D: it's late and no translation but are these what you're after?

February 19, 2013, 01:55 AM
Awesome info.

April 9, 2013, 12:35 PM
Really late to the party, but here's a quick translation.

Tolkachi Robotnik
April 9, 2013, 09:52 PM
You can also live with the trigger action as it usually is, a long take up, an obvious scritch or friction, and then you know it will go off directly if you keep pulling on it.

April 9, 2013, 10:20 PM
Careful bending that sear. I broke two of them before I got it right. In my last two builds I sprung for the Timney trigger. I also got a thumbhole stock for mine, though not from Boyds. I am in the process of a metal refinish, and am considering DIY parkerizing.

April 10, 2013, 11:30 AM
Alan LA
Clark, will the ATI take the abuse the Rock Solid mount will? By abuse, I mean recoil.

The mount will take the abuse.
As I said in the video, the stiffness is a function of the height cubed.
I built a mount that shook the reticle out of a Leupold 2x7.

The ATI design does not make that mistake. It has the height for the stiffness that raises the resonant frequency and reduces that amplitude of shaking.

I drill a third hole, because I pull the barrel, but it works fine with just the two holes.

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