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Discussion Starter · #21 ·
COMB

The raised comb of the Boyd’s Monte Carlo style stock is pretty but impractical.
Using the same stock on the M44 project, I left the comb at the original height.

While the M44 does have a recoil tube and LimbSaver pad, it still has a kick.
If you press the comb into your cheek too tightly, it will nip you quite solidly and painfully on the cheek bone.
Son, who is a lefty, finds the comb most annoying to a left handed shooter.
Small frame people tend to find it annoyingly high.
As evidenced by the wear mark,
The back of the comb routinely rubs against headphones and if it happens to pinch skin between the stock and the headphones, is extremely painful!
I plan on addressing this with a redo of this stock over the winter as this just has to be fixed!

In order to remedy this problem, I decided on a lower “Swept back” comb. The height was reduced a good ¾” in this area to provide adequate clearance for the headphones, just about flush with the rear section and a gentle hump in the middle.

Overall thickness at the top of the comb was reduced until son was comfortable with it left handed.
Grooves around the pistol grip were worked down for a better hand fit and grip.

Pics: M44 comb
Pics: M39 comb
 

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Discussion Starter · #22 ·
TRIGGER FINGER GROOVES

As seen in the original from the M44, the stock as it comes, extends down past the curvature of the trigger group.
Pic: original wood area trigger

I found this unsuitable to my grip and trigger pull with far too much “meat” in this area.
It was sanded out to match the curve of the metal on the trigger group.

On this stock, as it is intended to be a bench rest rifle with a particular hold and angle, I not only recessed this area but sanded a groove back towards the pistol grip that particularly suits my desired trigger finger position.
The same was done on the left side, fitting it particularly to my son’s left hand grip and longer finger.
The nice thing about a wood stock is the ability to shape it precisely to your hand and a grip that is comfortable for you.
Work slowly, in small increments, until you achieve the desired fit.
Pics: trigger area sanded
 

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Discussion Starter · #23 ·
RECOIL SUPPRESSION

*IMPORTANT
Before drilling for the recoil tube, mount the LimbSaver pad and check for correct stock length and shoulder fit. The pad will add 1” to overall length. If it is necessary to cut down the stock, this must be performed FIRST as it will be difficult to remove the tube and re-drill the hole later.
If you are mounting a scope, measure for correct eye relief and stock length with the scope mounted.

The only disadvantage of pillar post bedding is that it is so solid that all recoil is transmitted directly to the stock, and your shoulder! It actually magnifies the amount of felt recoil.
Recoil suppression will be mandatory unless you can stand shooting something akin to a steel beam hammered into your shoulder!
The M44, without recoil suppression was absolutely brutal!
The M39, with an even more solid mounting, would be an unforgiving battering ram without suppression!

For this gun, I chose a 16oz recoil tube, MR100785
On the M44 and the Hakim, I used the 10oz MR100345
http://www.precisionreloading.com/recoilsuppressors.htm

Pic: recoil tube

There are numerous “recoil tubes” out there. Some use a piston and oil combination like a car shock absorber. The Precision Reloading mercury filled tube is simply a hollow tube filled with mercury and an air space.
The objective is to place the tube with the rear end slightly down from level with the line of the bore so the mercury settles to the rear, in this case, about 2-3 degrees.
When fired, the mercury sloshes forwards as the stock travels backwards cancelling out movement and absorbing the recoil.
Plain and simple, it works as intended and this will be the third one I have used quite satisfactorily.
I was quite pleased with the performance of this recoil tube on the M44 and Hakim.
The rifles still have a kick, but it is reduced to a strong push rather than a bone jarring crack.
Combined with the LimbSaver pad, you can shoot it comfortably all day with no other recoil suppression or pads.

Additional weight was not a consideration for this rifle as it will be benched with a bipod.
There is quite a noticeable difference in weight and balance with the 16oz vs. the 10oz tubes.
The M44 balances perfectly when standing shouldered as it puts just the right amount of weight in the rear of the stock to make it level very easily. It actually helped make that gun ideal for standing quick shots as it comes to shoulder perfectly and is easier to keep the front sight on target for longer periods compared to a rifle that is front heavy.
The longer and heavier M39 barrel balances nicely with the 16oz tube but is overall a little on the heavy side.
Shooting both side by side, I don’t notice appreciable difference in felt recoil or significant increase in recoil reduction with the 16oz tube using 7.62x54R.

I am doing a similar bedding job for a friend on his .338 magnum. He needs heavy recoil suppression as that canon kicks butt! We have still not determined which tube will go in it and he has to decide on the tradeoff between weight and recoil as he intends to carry and hunt with that rifle. I am totally undecided and will leave the choice to him.

Mounting the tube is accomplished by drilling the appropriate size hole with a drill guide.
This drill guide can be found at Home Depot. Sorry, forgot the brand name and the price but they are not expensive and handy for a multitude of projects around the house.

Pic: drill jig

NOTE: On both of these stocks, I did not need to shorten the butt for the thickness of the LimbSaver pad for my shoulder fit and correct eye relief. You do want to check your own fit and eye relief before installing the tube in case you need to shorten the stock some.

Measure and mark the center line at the thickest portion of the stock.
Measure and mark the center line of the top to bottom distance.
Set the angle on the guide to 2-3 degrees off parallel with the top of the stock and barrel.
You want a very slight downhill angle on the rear so the mercury runs to the back of the tube.

Attach the drill guide by clamping it onto the stock, using wood screws and washers and drilling new screw holes, which can be filled with epoxy later. Securely anchor the drill guide to the butt of the stock with the point of your wood bit aligned with your previously measured cross marks.
Align the guide with the center vertical mark using the indicators on the guide. Screw down tightly.

The outer diameter of this tube is 7/8”. As the stock is very hard black walnut and you are drilling into end grain, I strongly suggest spending a few dollars on a new carbide wood bit that you know is sharp. You want this to bore cleanly without chattering in the hole and a dull bit is more trouble and effort than the cost of a brand new one.

Depth of the hole needs to exceed the 5” length of the tube as, due to the angle, it will not seat all the way unless you go at least 5 ¼” deep.
Measure the depth of the hole before inserting the tube and closely inspect it with a flashlight as any ridges created during drilling can cause the wrapper to wrinkle and make it stick. If necessary, ream out or sand the hole prior to inserting the tube.

The diameter of the tube is 7/8” but the outer label and wrapping will make it a very tight fit.
It needs to be carefully started and then tapped in with a rubber mallet until it is all the way in and does not protrude from the stock. One end of the tube has a ¼”x28 threaded hole that will accept a standard bolt. Make sure this end is facing the rear! If necessary to remove the tube once inserted, screw in a bolt and use a slide hammer puller to yank it out again.
Once the tube is inserted and properly seated, fill the back of the hole with wood epoxy filler and sand flush with the butt.
 

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Discussion Starter · #24 ·
LIMBSAVER PAD

Limbsaver Recoil Pad Grind to Fit Small 4-13/16" x 1-27/32" Rubber Black $34.99
http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=118987&t=11082005

I have been satisfied with Limbsaver pads.
The SMALL grind to fit pad is still very much oversized for this stock.
It will need to be marked and sanded down.

Place the pad against the butt and align for best overall fit.
Insert a punch into the screw holes on the pad and mark the holes.
The previous holes from the plastic butt plate that came on the stock may need to be filled with wood filler first as the Limbsaver holes will not line up with them.
Drill new starter holes and attach the pad with slightly larger flat head wood screws than those that came with the pad. I do not like the smaller wood screws that came with the pad as they don’t get a firm and solid grip in the wood. Use a larger and longer screw.

With the pad in place, check alignment. It may be necessary to ream the holes in the Limbsaver base for slight side to side adjustment. It will tighten down securely with flat head screws.
Once you attain the best possible alignment, scribe the area on the Limbsaver plate where it meets the wood. Scribe with an Exacto knife or other blade as pencil and pen marks are difficult to see and rub off.
Remove the pad.

Limbsaver’s suggestion to freeze the pad overnight seems to make little difference in sanding, in my experience.
As they suggest, sand the pad with a belt sander.
Do this outdoors as the plastic and rubber sanded off gets all over the place, makes quite a mess, and is very hard to clean up as it sticks to everything!
Hold the pad with the plate facing you and rotate it around against the sanding belt.
I found it is better to go front to back, from the plastic base to the rubber, rather than lengthwise where it will chatter and chew up the rubber.
Work the shape down to within 1/32” of your scribe mark, checking frequently against the stock for fit.

For final fitting, screw the pad firmly onto the stock and HAND SAND until flush with the wood.
You may have to remove it and use the belt sander or an orbital sander for faster removal of high spots, just be careful not to sand deeper than your scribe mark.
During final fitting, you will remove a little wood from the stock until the plastic of the mounting plate and the wood mate flush.
The rubber portion of the pad can be smoothed with hand sanding with fine grit.
 

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Discussion Starter · #25 ·
BOLT, TRIGGER, SEAR tuning

This is a subject with a considerable learning curve and I am still learning!
While a Mosin bolt is a very simple design, not all are created equal and there is considerable room for improvement. Simple design changes from the M91 through the late production models show considerable difference. Minor alterations in the style of trigger and the spring and sear totally alter the characteristics.
Remember that war production rifles were churned out in a hurry to meet demand!
They frequently exhibit signs of that stressed production with very crude workmanship and things like very coarse file marks. A very small amount of smoothing and polishing can go a long way to improving performance! The trick is learning what and where.

The difference between the ’70 and the ’67 was substantial and very hard to figure out.
The ’70, as received and straight out of the box, has one of the sweetest triggers of any Mosin, and for that matter, any rifle in our collection. It has a long travel which comes to a clear stop and then a very light and smooth let off. This is very characteristic of the original M91.
The ’67, as received, was comparable to any stock M91 or later Mosin trigger and nothing special about it. Bolt swapping among several rifles points out the subtle differences.
What was the considerable difference between the two?

Much study, with magnifying lens and calipers, showed that the ’70 had been worked by an expert who knew what they were doing. There was evidence that it had been stone polished.
The ’70 was most clearly someone’s prized “pet” and unlike any other Mosin I have ever shot!
A Mosin trigger and bolt are pretty much the same no matter what year or what rifle it came from, right?
Although I have become pretty adept at smoothing out a Mosin bolt and trigger tweaking, this puppy taught me some new tricks!
 

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Discussion Starter · #26 ·
Trigger

The original ’67 trigger was an early M91 style with the double pin rocker that rides on the spring. I don’t recall what year they abandoned this for the solid cast trigger.
Pic: both triggers

I found the difference rather interesting but since I intended to replace the trigger with a Huber anyway, I set it aside with little further notice.

Later on, I got to looking at it sitting on my desk and had to experiment with it by swapping it out with my custom M44 and doing a little more tweaking on that.
Decidedly smoother, it had quite a bit of travel and creep. It seriously lacked a full return after firing.
Noting the empty hole under the two pins, and a space under the spring, I got a roll pin and spring at the hardware store.
pic: spring and pin

The spring is cut to 5mm
The spring is inserted between the two pins and then held in place by the roll pin placed through the blank hole
Once secured and mounted on the trigger spring and screwed down on the receiver, it provides the necessary return for the trigger and eliminates much of the creep.
This modification has proved to be a much better trigger on the M44 that is extremely smooth with just the right amount of travel and tension.

But, back to the M39,
For a bench rest sniper, I was looking for a very light let off with about a 2lb pull or less.
The simple choice is a Huber trigger.
http://www.huberconcepts.com/Mosin-Nagant_Trigger_Replacement.htm

There are instructions out there, and posted previously in the forums, about making your own ball bearing anti-friction triggers.
The Huber, while a bit expensive, is a finely crafted piece worth the price.
What I prefer about it is the fine adjustment available with the tiny hex screw in the top.
You can set the trigger to exactly the let off tension you desire simply by removing the bolt and inserting the allen wrench in the screw. As little as 1/8 turn on the screw makes a vast difference in the pull. It can be set with little to no creep at all. In fact, go too far and the cocking lug will fail to engage the sear. Even as light as you dare go, you can’t make the trigger drop the pin by banging the rifle, a safety issue. I like it OMG light but had to add just a little more by backing out the screw in small increments until I got it just to my liking. It is still OMG with minimal travel and about 1.5 lb pull. Perfect for the bench or prone, it is a little too touchy for shoulder fire.
 

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Discussion Starter · #27 ·
Trigger Spring

http://www.surplusrifle.com/shooting2006/improvingm44carbines/index.asp

Follow the instructions in the above for lightening the spring by grinding to the indicated thickness.
Spring tension, and trigger pull weight have much to do with this tuning.
I have performed this on just about every Mosin I have with considerable improvements.
You can go a little too far, which I have not done to date, so it is a good idea to have a spare or two from Numrich in your parts inventory before you begin!

The easiest way to accomplish this is with the Dremel sanding drum.

The important part of this tweak, once you have achieved desired thickness by grinding both sides of the spring, is polishing the top surface where the trigger rides to mirror bright.

This is done by first hand rubbing with 1200 grit paper and then buffing with the Dremel and fine compound until all your grinding marks are completely polished out to mirror smooth.
On completion and final assembly, one tiny drop of Moly Fusion is applied to the surface to give the trigger a smooth as warm butter ride and protect the surface from rust.
 

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Discussion Starter · #28 ·
Firing pin spring

http://www.surplusrifle.com/shooting2006/improvingm44carbines/index.asp

Once again, follow the instructions for shortening the firing pin spring.
This considerably improves bolt function making it much easier to cycle and cock.
I have done this to all the Mosins and the other M39 with similar results.
This bolt cycles like a knife through warm butter and only requires two fingers to effortlessly chamber the next round. The pin will strike with sufficient force to light off the primer. The only failure to fire instances have been true duds where even multiple strikes failed to light them up.

As to "lock time", I have found that combined with the other bolt tuning and sear polishing tweaks, lock time is considerably faster even with the shortened firing pin spring.
 

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Discussion Starter · #29 ·
A brief intermission.
This is where I have to finish the rest of the tutorial.
More to come.
Sear and cocking lug tuning
Bolt and receiver tuning
Scope mounting
Bore conditioning
 

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Wow! Very impressive work. I look forward to the rest of your tutorial, especially the part about the machinist ripping you on that scope mount...bottom half looks like an Accumount. Nice to see what is possible with the M39. I'd love to take my M39/SOV Repro to that level of accuracy, but I don't have your skills nor the cash to spend.
 

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Discussion Starter · #31 ·
BORE CONDITIONING

How do you make a good and accurate rifle ten times better?
There are some tune up steps and treatments I have become a firm believer in, so much so that I have applied them to all my other “shooters”
Of course, the premise is that you are starting with a good bore with strong rifling that already shoots accurately.
I do not dismiss the accuracy of any rifle until it has been “properly” cleaned and conditioned and the crown and lap tuned up. I have had various milsurps that where fair to mediocre which suddenly gained a new life after the proper work and surprised me with new found accuracy.
I have “conditioned” rifles people swore were shot out and worthless only to obtain quite acceptable accuracy. In fact, I’ll be quite happy to buy that “worn out” milsurp for an appropriate pittance and gladly take it off your hands!

Bore Conditioning Cleaning

The first step in “conditioning” is a thorough scrubbing down to bare metal.
This is NOT running a few patches with Hoppes through it until the gunk comes out!
All traces of carbon and all copper and lead fouling must be completely removed.
DO remember to stock a supply of NEW brass brushes as, once crushed down and worn, they no longer reach into the grooves and you are only cleaning the lands!

There is a bit of Economics 101 here …
You can use many other products on the market in vast quantity with a huge labor and time investment. If they fail to do the job, your “conditioning” treatments will not be effective.
The below listed products are not the cheapest to buy but, when used in the order listed, you will consume small amounts of each stretching them far further than the other products for less money! There is also a huge reduction in the labor factor.

Chamber and Throat
Note that all steps below should be equally applied to the chamber and throat area, a part of the cleaning regimen often forgotten and ignored.
These areas need to be brushed during cleaning by finding appropriate size brass brushes that will fit tightly into them. The chamber is bigger than the throat so you will require several brushes. Crap in the throat is the usual cause of sticking empties that refuse to eject and the most common cause of broken extractors. Remember that the neck of the bullet expands slightly in the throat area upon firing to form the gas seal and considerable carbon and fouling will accumulate there. The easiest way to clean these areas is to place the brush on a short rod that will reach from the chamber end and chuck in an electric drill. Spin the brush for twenty seconds with the drill, change to the throat brush and spin that for twenty seconds.


Ingredient #1
The most essential cleaning product I use, in vast quantity, is Advanced Auto Parts Carb and Choke Cleaner. Although the price has taken a jump to $2.59 per can, it is still the cheapest solvent out there that works better than anything else I’ve found to date!
The contents of this product are designed to remove stubborn carbon deposits from engines.
It accomplishes the same job with the carbon deposits in a rifle bore.
Breaking up and removing the carbon also removes the trace metal copper and lead fouling that the carbon holds in place.
The Advanced Auto Parts cleaner has a slower rate of evaporation allowing more time to work with it. It will still eventually evaporate completely with no traces left behind.
It can damage wood finishes but is not as prone to dissolving them as many other products.
Whereas Gum Cutter will strip decades old paint in seconds after contact, this will not.
As one of the “cheapest” cleaning products that will remove 80% of carbon and fouling, it is worth always carrying a can with you to the range for a quick first clean up after shooting.

Step #1: Spray and flush the bore liberally with carb cleaner.
Stoke vigorously with a brass brush a good twenty times.
Flush liberally again with carb cleaner and watch the black junk pour out.
Work a dozen or so patches, soaked in carb cleaner through the bore scrubbing well until they no longer come out black.
Repeat with the flush and brush and again with patches until you no longer get anything out.
This step usually only requires two cycles on a “conditioned” bore and about fifteen minutes.
 

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Discussion Starter · #32 ·
Ingredient #2

Shooter’s Choice Bore Cleaner
http://www.shooters-choice.com/
I highly recommend ordering directly from the web site in the larger quantity bottles.
While some gun stores in the area do carry Shooter’s Choice products, they only have the small bottles and it is more economical to order directly off the web. While the large bottle is expensive, used in the small quantities here, you will get considerable mileage out of one.

We shoot a lot, which means we clean a lot! Over the years, we have tried just about everything on the market and just find Shooter’s Choice products to do a better job, for the money, than any other brand. Personal preference, choose what you want, but I will use nothing else!

Step #2
Following the carb cleaner, soak a patch in Shooter’s Choice Bore cleaner and thoroughly swab the bore. Let stand five minutes and then brush vigorously.
Flush again with carb cleaner and patches soaked with carb cleaner.
Patch again with bore cleaner and scrub with several more patches wet with carb cleaner.
Flush, brush, and patch again with carb cleaner.
Very little should be coming out on your patches by now. If not, repeat the cycle.
You should only require two or three patches soaked in Bore Cleaner.

Step #3 Ingredient #3
Shooters Choice Copper Cleaner
Many of the copper cleaner products on the market are extremely caustic with high levels of ammonia (ammonia dissolves copper – that is the blue that comes out on your patch).
Some of these products are downright damaging to your bore if not used strictly according to directions!
Shooter’s Choice Copper Cleaner is not damaging to the bore when used properly.
Soak a patch in copper cleaner and thoroughly swab the bore.
Let stand 1 (one) hour.
Flush, brush and patch with carb cleaner.
No blue or copper should be coming out on patches or still visible in the bore.
If not, repeat the cycle.

Step #4 Ingredient #4
Shooter’s Choice Extreme Cleaner
This is a more potent foaming bore cleaner. Somewhat effective at copper removal.
Insert the nozzle in the receiver end and spray until foam comes out.
Repeat from muzzle end.
Let stand 3 (three) hours.
Flush, brush and patch with carb cleaner again.
Repeat cycles until patches come out clean.

Step #5 Ingredient #5
Wipe Out Foaming Bore Cleaner http://www.eabco.com/WipeOut.htm
While this is probably the best product on the market, it is too expensive to use for regular cleaning duties. The small spray can goes a long way but, it is not practical for routine cleaning chores. Wipe Out will dissolve copper safely and it is safe to let it stand for long periods, in fact it is necessary to let it stand for proper chemical reaction.
Insert nozzle from receiver end and spray until foam comes out. Repeat from muzzle end.
Let stand for 3 (three) DAYS. You can speed up the time and reactivity by placing over a heater vent but it must stand at least twenty-four hours to do the job.
Pay attention to the foam that runs out either end. If it is blue, there is still copper in the bore.
Flush, brush, and patch with carb cleaner.
If you are still getting blue, go back to step #3.
It is often necessary to apply a minimum of 3 (three) treatments of Wipe Out for “bare metal” conditioning.

The bore should now be completely cleaned to bare metal and ready to condition.
 

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Discussion Starter · #33 ·
TUBB’S FINAL FINISH BORE CONDITIONING BULLETS

http://www.davidtubb.com/ff_tests.html
http://www.davidtubb.com/finalfinish.html

Read the technical specifications and the testimonials!
Believe what it says or not. I believe!
Having seen what these polishing bullets do to the bore and the improved accuracy, I am sold on them. Some calibers can be obtained in loaded cases, others like 7.62x54R (308 diameter) must be hand loaded.
For $34.95, what else can you buy so cheaply that will make a considerable improvement in your shooting?
For 7.62x54R hand loading, you will need decent Boxer primed brass. One of the cheapest solutions is Privi Partizan http://www.prvipartizan.com/. Just buy 50 loaded rounds and shoot them off. The brass will be pretty clean, without tumbling, for reloading and they will stand up to many reload cycles. Nice brass!

The loaded Final Finish bullets are fired ten rounds at a time progressing from one grade of grit to another, coarse to very fine.
Between each grit, thoroughly clean the bore following step #1 and step #2
After all fifty rounds, the bore should be very bright with distinct rifling.
It is now polished.

Bare metal condition again following all the cleaning steps and get down to bare metal with no residue of any kind remaining in the bore.

MOLYFUSION TREATMENT

http://www.shootersolutions.com/mol12ozkit.html

Once again, read the technical specifications and testimonials on the web site.
Believe or not! I believe!
Although I have no way of proving claims of improved accuracy, I can certainly swear how effective this product is when it comes to cleaning!
The product is PERMENANT! It binds with the actual metal and the only way to remove it is by grinding. It is a super lubricant! It is very good for treating any surfaces you want super slick, as in sears and bolts! One kit is enough to do many, many guns!

After complete Bore Conditioning and a treatment of MolyFusion, cleaning time will be reduced by 2/3! Very simply, crap no stick! Copper and lead fouling is vastly reduced as it no longer adheres to the bore. Guns, shot heavily all day, come clean in just a few minutes with cleaning steps #1 and #2. Just step #1 with carb cleaner removes 80% of accumulated carbon deposits.

CAUTION!!!
Do NOT allow MolyFusion to enter the chamber and throat area!
Read the cautionary statements in the technical specifications.
A certain amount of friction is required between the case of the bullet and the walls of the chamber and throat. Removing that with MolyFusion can cause very DANGEROUS stress on the bolt. This is absolutely essential for semi-automatics where recoil operation requires a certain amount of delay caused by friction.
Unless you want to risk wearing the bolt, make and insert an appropriate DUMMY round into the chamber during application and do not allow your mop to enter the chamber. A dummy can be made by stuffing an empty case with cigarette filters allowing one to protrude slightly from the neck. The filter material will absorb any MolyFusion that seeps into that area.

To treat the bore, buy a new mop. Apply a few drops of MolyFusion at a time with a toothpick until the mop is saturated. Stroke the bore with it several times, rotating the mop as you pull it out to ensure all surfaces get evenly coated.
Let stand 24 hours.
Flush and patch with carb cleaner.
Repeat twice more.

A proper and thorough application will turn the bright shiny bore a dull gray.
Than means it has bonded with and adhered to the metal.
While MolyFusion is permanent, it is advisable to repeat the extreme bore conditioning cleaning and application of MolyFusion twice yearly if you shoot a lot. The kit comes with oil mixed with MolyFusion that is good for a light oiling of the bore before storing. The small amount of MolyFusion in the oil will refresh and preserve the original treatment as well as effectively preventing rust. Read the testimonials and tests on corrosion prevention properties of MolyFusion. I have not seen any rust come out of bores that have been treated.

Note: Apply the MolyFusion AFTER doing the lap and crown.
 

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Discussion Starter · #34 ·
LAP and CROWN

The muzzle end of the bore is the most critical factor in accuracy!
You have polished and conditioned the rifling in the bore to the best you can hope to achieve with it but the slightest nick in the crown will spray your bullets all over the place!

At the precise instant where the bullet disengages from the rifling, there is a huge high pressure volume of expanding gas behind it from the burning powder. As that gas begins to exit the muzzle behind the bullet, it must exit in a perfectly even and concentric circle.
Look up “smoke rings” and smoke ring generators on the web and watch the videos demonstrating how the smoke ring is formed. Note that it should be a perfect donut ring rolling back in on itself. The gas exiting behind your bullet must behave in similar fashion!
The slightest nick or ding in the crown can disrupt this gas flow leading to turbulence.
At the point of the turbulence, the gas will exert more pressure on one side of the tail end of the bullet causing it to yaw in flight. Yawing bullets do not fly true!

When analyzing a spready pattern from a gun that appears to be spraying all over the place with no consistency, it usually points to a problem with the lap and crown.
As compared to vertical or horizontal stringing with a consistent and repeatable pattern, crown and lap problems appear totally random. “Flyers” can frequently be attributed to crown and lap problems when the bullet gets tipped of course as it exits the barrel.

Most milsurp rifles will exhibit some form of crown damage from handling, use and storage.
Even new rifles can accumulate slight buildup of copper and lead fouling deposits at the critical lap juncture sufficient to cause “flyers” and spready groups.
It is important to very closely inspect this area with a strong light and a high magnification lens strong enough to observe even the smallest nicks and scratches.

If the imperfections and dings are small enough, they can easily be polished out without resorting to a re-crown job. Crown cutter kits are an expensive investment if you are not doing a lot of them, will still require polishing, and extremely expensive if performed by a gunsmith.
Polishing is usually sufficient to return the gun to accuracy if you pay attention to detail.

Step #1:
Closely inspect the crown and highlight any imperfections with a dry erase marker. When lightly rubbed off, it will leave visible traces behind in any nicks and dings.
The outer surfaces of the crown can be successfully polished and imperfections ground out using a Dremel with various grit compound ROUND wheels. The trick is matching the angle of the crown with the rotating wheel while rotating the barrel or Dremel so all areas are buffed evenly.
This is a little more difficult to do with a 45 degree target crown and you may have to alter a Dremel buffing wheel to the correct angle to match.

Step #2:
Continue to buff and inspect with each grit until imperfections have been buffed out and are no longer visible. Progress to finer grits up to final buffing with very fine red jewelers rouge (the small red Dremel container). For final mirror bright polishing, add a few drops of honing oil to the compound in the container and spin the buffing wheel in it to apply to the buffer. It should have a thin and oily consistency. This will remove bluing from the crown area. It is of no consequence to leave it “bare” and apply a thin dab of oil with your finger tip when done or apply MolyFusion which will prevent rust. The crown should be perfectly mirror bright all the way to the outer edges where it rounds over to the barrel shank.

Note that for deep or severe nicks and gouges, it may be necessary to round the end of a wooden dowel to the matching angle and use it to twirl a small piece of fine grit sandpaper. Common hardware items, such as an “eye hook” will often fit correctly over the outer surface. Being rounded, the eye hook can be coated with compound and used to polish the “round over” outer diameter.

Lapping

Here is the “secret” and most important part!
The critical juncture where rifling ends and begins the crown is the most important point.
This transition area must be perfectly even and concentric.

DO NOT, as is often suggested, perform this with a brass screw from the hardware store or any type of power tool or drill! It takes a very minimal amount of time and effort, by hand, with the right tool and without risk of causing extensive damage that will require re-crowning.

Order several caliber specific lapping tools from http://midwayusa.com/
Just search LAPPING on the site and it will take you to the page.
These are only $7.99 so buy a couple and discard them when worn.

The brass lapping tool is important for two reasons.
It is a rounded ball, unlike a screw which may not be perfectly concentric.
Soft brass is necessary so that the compound works into and adheres to the polishing surface of the tool. Without the proper softness in the brass, the compound will not adhere and “work” the mating surfaces.

Step #1:
Purchase a small tube of valve grinding compound at the local auto supply store.
Wipe the crown area with a patch soaked in carb cleaner.
Apply a small dab of compound to the ball of the tool and spread it evenly around.
Holding the tool between thumb and forefinger, twirl the tool back and forth for twenty or thirty seconds while rotating the angle with your hand so that it is constantly changing and not wearing an uneven groove in the ball head. Utilize the entire surface of the ball.
Wipe the area clean with a patch soaked in carb cleaner and remove all compound.
You should see a very narrow gray “ring” starting to appear between the rifling and the highly polished crown.
Repeat once or twice until you have a very distinct and even gray “ring” roughly 0.75-1mm wide.
Wipe the crown and the tool clean with patches soaked in carb cleaner to get off all rough grit compound.

Step #2:
Using the fine red compound, thin with a little honing oil and smear a dab on the ball of the tool.
Repeat the procedure until the “ring” comes up mirror bright.
Invert the barrel and spray liberally from the receiver end with carb cleaner.
Patch from the receiver end with patches soaked in carb cleaner, discarding as they exit the muzzle so as not to draw it back into the bore, until all compound has been removed.
Coat the lap and crown with oil or MolyFusion.

Lapping is such a critical component of accuracy that every gun I shoot gets lapped!
I have had this “cure” several very sporadic shooting and well worn milsurps and halve group sizes or eliminate “flyers”.
We carry the tool and the compounds in our range box and have often done a quick lap job on someone’s poor shooting rifle with immediate and dramatic improvements!

It may need to be repeated!
Keep an eye on your lap and crown and whenever the “ring” is no longer mirror bright, give it a little touch up with the lapping tool! Don’t forget to inspect for dings and scratches whenever the muzzle comes into contact with something while handling or shooting.

Note that lapping also works with counter bores and muzzle brakes!
For any removable muzzle brake, lap the barrel where the rifling ends as well as the inside and outside of the brake.
For a rifle with a counter bore, find a tool small enough to reach down inside the counter bore and do that as well as the muzzle end at the crown.

Pic: Lapping Tool
Pic: crown with dings before polishing
Pic: crown after polishing
 

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Awesome project!! Im buying an M39 of my own from online within the next couple of days. I'll be getting a '67 unissed with "new bore". I'm really hope to follow your thread and do most if not all of the things you described. I very much look forward to any updates on the progress of this rifle as well as (hopefully!) some detailed instructions on how to do it. Thanks for all the helpful advice.
 

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It seems like you know what you are doing..........I have a M-N 91/30 now but I have been looking at the m39 to turn into a sporter......I have a problem with my hands as I am older, pulling back the safety on the M-N.....I have found that Timney makes a triger assembly with a saftey on it that can be installed into the 91/30. So my question is, will that same triger group from Timney fit into the M39.........I am looking for a shorted rifle to get into the bursh a litter deeper. And The m39 looks like the way I want to go, If this can be done..Thanks
 

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For those of you who may want a pristine barreled m39 action, I have a 1944 in new condition. It's a HEX receiver, and is really nice. Has a few spots where the bluing is off, but otherwise perfect. Asking $275. Contact me soon as there is a gunshow next weekend in New Bern, and it's going with me if not sold here.

Contact me direct at the following email [email protected]
 
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