Accurizing the Mosin Nagant 91/30 Rifle
(Cork Kit Instructions)
Thank you for your purchase of a Mosin Nagant 91/30 “accurizing” kit. I have gathered this information through many surplus rifle forums, Soviet sniper manuals, and my own experiences. The Mosin Nagant is an outstanding rifle for the money and can be tuned into an accurate enjoyable surplus rifle. I am not a gunsmith and accept no legal responsibility for your rifle or the actions of your rifle. I am not doing the work; I am only instructing you on how to complete the “accurizing” process. If you have any questions regarding this process please feel free to contact me at . Please also feel free to give me your feedback and to share your results.
During WW2 Soviet Snipers and armorers used certain techniques to increase accuracy of the Mosin Nagant 91/30 rifles. These techniques were also used by Finnish armorers who had captured and reworked Soviet rifles. They used what they could get a hold of when supplies were limited. Shims were mostly made of galvanized scrap metal, stripper clips, or pieces of food/ammunition cans. Barrel wraps were created out of uniform cloth or canvas, and even cork or thin cardboard. These simple materials can be used to tighten groupings and make your rifle perform better and a lot more fun to shoot.
“Accurizing” is an attempt to tune your rifle so that the barrel harmonics are not affected when a round is fired. Harmonics can be affected by uneven pressure points where the barrel/receiver and stock come in to contact. By following these instructions and minimizing or eliminating pressure points better accuracy can be obtained. I would also advise you to use the same ammo on every range outing to have one less variable present. For best results you will want to shoot and check accuracy after each step. Please also note that accuracy with any firearm depends on the shooters skill level, ammunition quality, trigger pull, and bore condition.
-Slotted screwdriver (Inch pound screwdriver optional)
-1/2” Deep well socket
-100 grit sandpaper
-8” x 1-1/2” Piece of paper or dollar bill
-Blue Loctite (optional)
-Rubber Cement or a house hold glue to hold shims in place (optional)
The first thing you want to do with your Mosin Nagant 91/30 is disassemble the entire rifle and give it a good cleaning. This includes taking apart the bolt and cleaning that as well. Most of these rifles have gone through a refurbish process and have been coated in cosmoline. By removing any existing cosmoline, gunk, or dirt you ensure that all of your mating surfaces are good and it gives you the opportunity to inspect the rifle. You want to look for any stripped screws, obvious damage, and bore condition. This also gives you the chance to inspect the stock for any shimming done by the factory, which may mean less work for you. Make sure you use oil where necessary during reassembly. Once assembled check the barrel bands to see how snug they mate with the barrel band springs. The hand guard has a tendency to “walk” once the rifle heats up and this can hinder accuracy. Slight bending and/or filing of catch points may be necessary to ensure the barrel bands are locked and the hand guard is secure.
Now that your rifle is clean you want to obtain a baseline for its accuracy. It has been said that these rifles were sighted in at the armory with a bayonet attached which will affect barrel harmonics and accuracy. Unless you intend on shooting your rifle with a bayonet attached you may have to adjust the front sight over. This can be done by using a brass punch and adjusting the sight dovetail, or you can purchase a Mosin Nagant 91/30 sight tool online. This will fit over the barrel and allow you to adjust the sight dovetail either way using screws. I would recommend starting out shooting seated at the 50 yard range with 147-149 grain light ball ammunition (checking elevation should be made at 100 yards, if it is off filing of the front sight post or replacement to a taller or adjustable post may be necessary). It has been said that when supporting your rifle you want to rest the stock on a shooting rest right below the rear sight. This once again is to minimize harmonics. Take 5-10 shots at your target to get a feel for your rifle and give the barreled action a chance to bed since the rifle was fully disassembled. Let the rifle cool and re check the tightness of the action screws. From this point on I would get in the habit of torqueing the front and rear action screws 35 inch pounds. A screwdriver which measures inch pounds may be a good investment at this point. Many have stated that they prefer the Wheeler Firearms Accurizing Torque (F.A.T.) Wrench. Next shoot a few groups of five rounds at separate targets or different points on your target. Be sure to not fire too fast and take a break after each group of five so that the barrel doesn’t get too hot. Heat is another variable that can affect accuracy. Mosin Nagants are notorious for the action screws loosening up during use; this can also dramatically affect accuracy. Be sure to check them after every five shots. You may also notice that with each group of five there is a “flier”, or a round that is stray. This is common with this rifle and should improve with the “accurizing”. Measure the grouping span on the target and this is your baseline. Be sure to save your targets for later comparison. Be sure to give your rifle an intense cleaning after your range session, ESPECIALLY if using corrosive surplus ammunition.
After your rifle is clean and reassembled and you have your baseline accuracy you can begin the “accurizing” process. The first objective is to try and address the loosening action screws by installing the front and rear trigger guard/magazine well shims. These shims have been laser cut and fitted to a rifle but may need slight trimming or filing to work for your application. Keep in mind that it may be necessary to use multiple shims by stacking them during the accurization process. The shims will help against compression of the wood and will also help keep the front and rear action screws from loosening. The shims can also help prevent the action screws from bottoming out before the action is tight in the stock. Later on after the entire “accurizing” process is complete you may use a small amount of blue Loctite on these screws. DO NOT USE LOCTITE UNTIL YOU ARE FINNISHED ACCURIZING. Now since you have changed another variable with your rifle you should repeat the shooting range steps as described in Step 2. Remember to save your target for comparison and measure your group size. Give your rifle a thorough cleaning and oil as needed.
*See the included images to see where to confirm that you have acheieved a 1-3mm clearance between the trigger guard and barreled action to be within specification. Keep in mind that your clearance will likely increase when the rear tang and recoil pad shims are added in the following step.*
After your rifle is clean and has the trigger guard/magazine well shims are installed it is now time to move to the next objective. This objective will require the most amount of time due to test fitting. Throughout the years wooden stocks can swell or warp when heat, moisture, or pressure is applied. It is because of this that many refurbished Mosin Nagant stocks make contact with the barrel, thus affecting harmonics. The goal here is to “float” the barrel. Modern day rifles have a “floating” barrel to improve accuracy. This occurs through the reduction or elimination of pressure points. Start by loosening the receiver screws and seeing if there is any front to rear motion. If there is the recoil lug may not be seating tightly in the inlet and may require a shim. It is not very common but I have come across this situation before. If necessary trim metal to fit recoil lug inlet, it may be a good idea to use an adhesive to hold in place since it will be on end and the barreled action will be removed frequently. If you do not have any scrap metal you can trim down one of the ¾”x ¾” metal shims included in the kit and use that. Once the recoil lug is tight in the inlet it is time to shim the receiver. Remove the barreled action and place the rear tang shim at the rear tang inlet, and the ¾ x ¾ square shim on top of where the recoil cross bolt is in the stock. This is known as the historically accurate method. Another optional placement for the ¾” x ¾” square shim is to trim it to fit underneath the recoil lug and drill a hole for the front action screw (please note that this is a newer approach to the accurization process). These shims have been laser cut and fitted to a rifle but may need slight trimming or filing to work for your application. Once again keep in mind that it may be necessary to use multiple shims by stacking them during the accurization process. The rear tang and rear of the receiver should be inspected to see if there is any contact with the wooden stock (see images). Contact can affect accuracy and these points of the stock should be filed for best results. The supplied 1/16" (1.70mm) cork can now be applied to the stock (see images to see the proper locations). Please remember that some slight trimming may be necessary for an ideal fit. The 2" x 1-7/8" "peel and stick" cork should be installed in the area just infront of the recoil lug notch. The 2" x 1-7/16" "peel and stick" cork should be installed at the front barrel band attachment point. This will create and area at the front barrel band where it clamps and compresses around the barrel. *Mosin enthusiasts have had positive results using a strip of cork gasket material or poster board on the underside of the barrel inside the channel to create an upward pressure on the barrel. Some have used cork gasket material or poster board on the hand guard at the same location to create a downward pressure on the barrel. Some have used both at the same time which can create more of a damper effect (like the original oiled canvas wrap). Because of this you may want to test your rifle with different combinations of cork installation to see what performs best.* Once the shims and cork are in place reassemble the rifle, leaving the upper hand guard and barrel bands off. Make sure your receiver screws are tightened to 35 inch pounds and re inspect the rear tang/rear receiver area for stock clearance. If filing is needed mark locations with masking tape. At this point all shims are in place along with the cork and it is time to check the stock clearance. Using an 8” x 1-1/2” strip of paper (you can use a dollar bill for greater clearance) attempt to slip the paper in between the stock and barrel at the muzzle end. While keeping it tight to the barrel attempt to slide it up towards the receiver. Any place where the paper snags is a pressure point, and should be marked with masking tape. Once the problem areas are marked the barreled receiver should be removed from the stock and the barrel channel should be clearance. This can be done using a ½” deep well socket wrapped in 100 grit sandpaper to sand the barrel channel. This is the point where the “accurizing” process becomes extremely repetitive. A lot of sanding and reassembly, then checking barrel to stock clearance. This process should be repeated until the strip of paper can move from the barrel wrap to where the barrel meets the receiver. Attention should also be given to the upper hand guard, as it may need to be clearance as well but would be difficult to accurately check. Once you are satisfied with the barrel channel clearance you can put the upper hand guard on. The front barrel band should be VERY snug, as I stated you want this point to compress the barrel. You can check how snug by checking for play in between the barrel, the stock, and the hand guard on the muzzle end of the rifle. Now that you have a “floated” barrel it is time to repeat Step 2 and test for accuracy. Remember to save your target for comparison and measure your group size. Give your rifle a thorough cleaning and oil as needed.
Enjoy your rifle! Take it to the range and attempt to hit further targets. Pay attention to your receiver screws and keep your rifle clean. Accuracy can be increased further through aftermarket or tuned factory triggers and different ammunition. You may find that surplus ammunition from one country shoots smaller groups than the same grain ammo from another. You can also attempt hand loading your own ammunition to control production variables found in factory and surplus ammunition.
If you are happy with the Accurizing Kit please spread the word.