Accurizing the Mauser Rifle
Thank you for your purchase of a Mauser Accurizing Kit. I have gathered this information through many surplus rifle forums, Mauser rifle books, German ordnance documents, and my own experiences. The Mauser rifle is outstanding for the money and can be tuned into a more accurate and 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. These shims are laser cut 26 guage galvanized steel and are made in the USA. If you have any questions regarding this process please feel free to contact me at Milsurpaccuracyinc.com or Raupleminze@yahoo.com. Please also feel free to give me your feedback and to share your results.
Engineers and armorers made sure that the Mauser rifle was manufactured within certain specifications during production. However, many rifles lose accuracy over time. This can be for a number of reasons. For some rifles it can be a worn out bore or a damaged crown. Such problems would have to be addressed by a qualified gunsmith. However, a lot of rifles have accuracy issues as a result of poor stock fitment. This problem is caused by a number of reasons. Most commonly it is due to wood compression and/or mismatched parts being used together. Russian capture rifles are a prime example of these issues, but they can be common on other capture rifles and even veteran bring backs. Accurizing is the answer to put these rifles back into specification and restore their accuracy.
Accurizing is an attempt to tune your rifle so that the barrel harmonics do not affect accuracy when a round is fired. Barrel harmonics can be affected by uneven pressure points where the barrel/receiver and stock come into 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/crown condition.
-Quality set of slotted screwdrivers
-Deep well socket set
-100 grit sandpaper
-Sheet of paper
-Rubber cement, house hold glue, or Rust Inhibiting Grease (RIG) to hold shims in place (optional)
-Super glue/epoxy (may not be needed)
The first thing that you want to do with your Mauser rifle is disassemble the entire rifle and give it a good cleaning. This includes taking apart the bolt and cleaning that as well. At some point a lot of these rifles have gone through a refurbish process and were coated in cosmoline afterwards. Or they may have also been coated with dirt and grime from sitting in an attic, closet, basement, or garage for years. 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 your rifle. You want to look for any stripped or missing screws ("capture" screws), obvious damage, and bore/crown condition. This also gives you the chance to inspect the stock for any shimming previously done, cracks in the stock, or repairs that were made. While inspecting the stock look for any dark spots in the channel near the bayonet lug and the forward band area of the hand guard. Dark spots in these areas are likely indications of barrel contact points.
During reassembly of your rifle place the action in the stock and check for any forward or rearward movement. Movement of the action may indicate excessive wear of the recoil lug socket of the stock and may require shimming. This should be corrected before firing the rifle as the recoil may damage the stock. An easy way to repair the stock is to ad a shim/shims to the face of the recoil crossbolt. Shims can be created out of brass sheeting found at your local hardware store. You can also trim down one of the extra square shims from your Accurizing Kit (if you can spare one). The shim(s) can be glued in place using super glue/epoxy.
Next you want to check if the action "rocks" in the stock at all. While the action is sitting in the stock apply downward pressure to the tang of the receiver and on the barrel just in front of the rear sight. If the action "rocks" on the recoil lug you will need to shim underneath the rear tang during the process. If it does not rock you may still need to shim, this will be determined later in the process. There is no need to add any shims underneath the action at this point, just make note of your findings. Shims will be added after your baseline accuracy results are obtained.
As you are assembling your rifle remember to start each action screw but tighten the front action screw FIRST. Take notice if your action screws are properly "timed" for the capture screws. This will likely change with the addition of shims. Also once the rear barrel band is in place check to see if there is any barrel to hand guard contact. Also look for barrel contact with the front band and the bayonet lug. These areas will likely have to be relieved or "honed" for proper barrel clearance. Also check to see that you have proper contact between the rear barrel band and barrel band spring so that no movement is allowed during recoil. With all of the problem areas noted make sure your rifle is fully assembled and oiled properly (except capture screws).
Now that your rifle is clean you want to obtain a baseline for its accuracy before you begin the Accurizing process. I would recommend starting out shooting seated at the 50 yard range with 196 grain ammunition. Lighter grain ammunition will work, but these rifles were designed to use heavier projectiles. When choosing a target I would suggest using a large one, especially if you have never fired the rifle before. Using a target that is 24"x 24" or 24"x 36" is ideal. That way you can see where the rifle "prints" even if the sights are off. Make sure that your rear sight is set to 100 meters, it will likely shoot high at 50 yards. It has been found that while supporting your rifle you want to place the stock on a rest at the "belly" of the stock. This is usually found in the area in between the receiver ring and rear sights. This practice is done to minimize harmonics.
While using the SAME aim point take 5 shots to get a feel for the rifle, check it for proper function/cycling, and allow the action to bed in the stock. Attempt to tighten the action screws starting with the front screw FIRST. At this point you can install the capture screws. Your may notice that your sights are not zero'd, this is normal. When the rifle is Accurized the point of impact may change, you can zero them when the process is complete. This is why I recommend using the same point of aim for all shots. You are shooting for a baseline group size, not points. If you try to use hold over or "Kentucky windage" you will not have an accurate baseline. Next shoot a few groups of 5 rounds at separate targets or different points of aim on the target. Heat is another variable that can affect accuracy. Be sure not to fire too fast and take a break after each group of 5 so that the barrel doesn't get too hot. I usually allow 30-60 seconds in between shots. Measure the span of the groups on the target, this is your baseline accuracy. 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 Mauser is clean and you have obtained your baseline accuracy you can begin the Accurizing process. This step will require the most amount of time due to sanding, test fitting, assembly, disassembly, etc.
Throughout the years wooden stocks can swell or warp when heat, moisture, and/or pressure is applied. Combine that with Mauser's that may have poor fitment due to mismatched parts during refurbishment (i.e. Russian capture) and it is no wonder why they are out of specification. These stocks are now over 70 years old, the wood shrinkage/wood compression that has occurred has stabilized and can now be returned to factory specifications. Many of these rifles have stocks, hand guards, and/or barrel bands that make contact with the barrel, thus affecting harmonics and reducing accuracy/consistency. Modern day rifles have a "floating" barrel for proper barrel harmonics. Proper barrel harmonics are essential in having an accurate rifle. The goal here is to put the rifle back into specification, "free float" the barrel, and increase accuracy/consistency.
First remove the barreled action and install the rear tang shim onto the receiver. You can also place the square recoil pad shim on the flat area of the stock on top of the recoil crossbolt. The shims have been test fit on several receivers but may require slight filing or trimming to fit your rifle. You can use a small amount of RIG to hold the shims in place. Now it is time to place the small cork piece in the barrel channel just before the metal of the bayonet lug. This is to create a small upward pressure point and dampen barrel vibration. Place the barreled action back into the stock and reassemble the rifle remembering to tighten the front action screw FIRST. While the hand guard and barrel bands are removed use the scissors to cut a strip of paper approximately 1" x 8" to check that the barrel is "free floated". Feed the paper in between the barrel and stock at the hand guard retainer on the rear sight. While pulling upward against the barrel slide the paper toward the front sight to make sure there is no contact until the paper hits the small piece of cork providing upward pressure. Any places that snag the paper can be marked on the stock using small pieces of masking tape. These are pressure points and will need to be removed. Repeat the paper test on the area from the receiver ring towards the rear sight. Once again any places that snag the paper can be marked on the stock using small pieces of masking tape. The area(s) of the barrel channel marked with masking tape can then be sanded using the 100 grit sandpaper rolled around an appropriate size deep well socket. The area between the barrel and the bayonet lug should also be checked with the strip of paper. If this area needs clearancing it can be done by one three ways. An additional piece of cork can be stacked on top of the cork piece in place, or the existing piece can be replaced with a thicker strip of cork. Or the channel on top of the bayonet lug can be honed SLOWLY with an appropriate size deep well socket and 100 grit sandpaper. Once clearance is achieved by sanding the bare metal area should be re blued, painted, or coated in RIG to prevent corrosion.
If you have areas that require clearancing you can disassemble the rifle and begin to address them. Work SLOWLY and take your time. Removing material is a lot easier than adding material. You also have the option of adding another shim to one or both areas as long as the action does not "rock" after they are installed. Keep in mind that multiple shims might also create barrel to hand guard and barrel to barrel band contact that didn't exist earlier. This is the part that becomes a balancing act between no stock clearance and too much stock clearance. However, slight hand guard and barrel band contact with the barrel can be addressed by honing the inside of the hand guard and band with the appropriate size deep well socket and sandpaper.
Reassemble the rifle (except the hand guard and barrel bands) and give it the paper test. It may be necessary to disassemble and sand multiple times until there are no barrel to stock contact points besides the cork piece providing the upward pressure. Once this is accomplished it is time to check that there is no contact between the stock and the hand guard retainer located on the rear sight (German models). You can also check this area with a strip of paper which should move freely in between the stock and retainer. If you have barrel to stock clearance you should have retainer to stock clearance at this point. If you do not additional shims may be required.
Install the hand guard and rear barrel band. Use a small strip of paper to check for clearance in between the hand guard and barrel at the rear barrel band. A lot of times sanding will be necessary, especially if there are dark spots on the channel of the hand guard from barrel contact. Working SLOWLY use the appropriate size deep well socket and 100 grit sand paper to clearance the channel. Re install the hand guard and test fit with the band installed. Repeat the steps until the paper fits in between the top of the barrel and the hand guard.
Install the front barrel band on the rifle making sure that the band spring retainer tab is locked in the band. Use a small strip of paper to check for clearance in between the top of the barrel and the front barrel band. If there is no clearance remove the band. Working SLOWLY use the appropriate size deep well socket and 100 grit sandpaper to hone the inside of the barrel band. Re install the front barrel band and check for clearance using the paper strip once again. Repeat the steps until the paper fits in between the barrel and front barrel band. If honing of the barrel band was done it may be necessary to re blue, paint, or coat the inside of the barrel band with RIG to protect the metal from corrosion.
***It is also possible that the small piece of cork that provides upward pressure may be creating too much pressure which makes the barrel to front barrel band clearance near impossible. In such a case you can experiment with removing the front cork piece and replacing it with small pieces of oiled business card (or the envelope your order came in). You can start with one layer or fold pieces accordingly to achieve the needed "balance" of clearance to put your rifle into specification.***
After your barrel is "free floated" you can now work on the bottom end. The first objective is to try and correct any wood compression or bottoming out of the action screws by putting the trigger guard and receiver in specification. If the wood has been compressed the action screws could be bottoming out before things are tight. In such an instance the receiver could be loose and the stock could become damaged.
There should be a slight gap in between the top of the trigger guard "magazine well" and the bottom of the receiver. I would recommend starting with at least one shim per location on the trigger guard (1 rear trigger guard and 1 front trigger guard). The shims have been laser cut and fit to most trigger guards and receivers but may require some filing or trimming. The shims can be held in place during assembly by using rubber cement, household glue, or RIG. You can test for proper clearance by reinstalling the action in the stock and tightening the action screws (front FIRST). Then remove the bolt and trigger guard floor plate. Next insert an "L" shaped piece of paper through the "magazine well" and check that it fits between the top of the trigger guard and bottom of the receiver. If the paper gets snagged or doesn't fit in between it may be necessary to add multiple shims per location. You can do so by simply stacking the shims on top of each other.
Once your trigger guard "magazine well" and receiver clearance is established your rifle is in specification.
Now that your Mauser is Accurized and in specifications it is time to test it out at the range again. When testing your rifle at the range it is important to maintain the same procedures used when the baseline accuracy was obtained. You should shoot the rifle seated from a bench at 50 yards with the rear sight set on 100 meters. Be sure to rest the stock on the "belly" and shoot the same type of ammunition. Make sure you once again use the same point of aim throughout. You will notice an improvement in the accuracy and consistency of your rifle. At this point you can zero your front sights. Some people like to use a punch and drift the sight over accordingly. I feel that makes things too difficult to make slight, controlled adjustments. I would recommend purchasing a Mauser front sight tool which fits on the barrel and uses screws to push the front sight over. Just remember to remove it while firing, the sight tool will change the harmonics of the barrel. So adjustments must be made, then the tool removed before a confirmation shot. Compare your targets and see how the group size is now smaller. That is the difference that an Accurized rifle in specification will have over one that is not.
Enjoy your rifle! Take it to the range and attempt to hit further targets. Accuracy can be increases 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 your Mauser Accurizing Kit please let me know, and spread the word.
Here are the specifications for the Mauser rifle from the German Ordnance Documents:
1. Bayonet lug to clear barrel by .2mm.
2. Forward part of stock channel to bear upward against barrel lightly.
3. Tapered part of stock channel forward of rear sight and shoulder on forward part of this tapered section to clear barrel all the way around by .5mm.
4. Rear cylindrical section of stock channel to clear barrel by .5mm, except at top edge of channel where it can lightly contact barrel and sight base.
5. Recoil lug on bottom of receiver to fit stock uniformly and tightly. Recoil lug must bear firmly against recoil shoulder (recoil crossbolt) on stock.
6. 20mm at bottom rear end of receiver tang to contact stock firmly.
7. 25mm at rear and 20mm at front of trigger guard to contact stock tightly.
8. Front end of sight base projection which retains hand guard must clear top of the stock by .3mm.