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LAPLAPING THE LUGS OF A MAUSER BOLT ACTION RIFLE

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72 usmc
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LAPLAPING THE LUGS OF A MAUSER BOLT ACTION RIFLE

#1 Post by 72 usmc » Tue Dec 11, 2018 7:53 pm

This is a repost of Metzler's sticky "LAPPING THE LUGS OF A MAUSER BOLT ACTION RIFLE". He must have paid photo bucket to allow his pictures to remain on the Wayback. This was one of the greats so I am reposting the first part lacking comments. This is his meat of the post. Pictures will be fixed by the forum method and I think they should stay independent of photo bucket. It will be reposted in sections to allow for the 5 photo limit per post. This is a direct copy & paste except I re added his photos through the forum.

Here is the Wayback link, if it works, of the old original sticky & original comments. SEE
https://web.archive.org/web/20170318224 ... 15edfbecef


Metzler 15 May 2009


LAPPING THE LUGS OF A MAUSER BOLT ACTION RIFLE

I recently received a Swedish Mauser barreled action that was put together from a new old stock (NOS) receiver and NOS barrel in 6.5x55. The first thing I did when I unpacked it was check headspace with my Forster Go/No-Go Gauges. Right off the bat, it wouldn’t pass the Go Gauge (Figure 1). I then dyed the lugs and worked them in the receiver and found that the left lug (Figure 2) was contacting only about 40% and the right lug was not contacting at all.

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Fig. 1- First attempt to close the bolt on a 6.5x55 Go Gauge
fig1.jpg
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Fig. 2- Dyed bolt lugs showing very little contact
fig2.jpg
After much online research and asking questions, I decided to lap the lugs. This does two things; first it increases headspace so the bolt will pass Go gauge. Secondly, it ensures a good flat fit between the working surfaces of the bolt lugs and the receiver lugs. Lapping consists of introducing a grinding medium between both sets of lugs and working the bolt up and down. This takes metal off the lugs. To check progress, a layout bluing dye (non-permanent) is applied to the bolt lugs and the bolt is worked up and down. When the bolt is removed, you can see where the bluing dye has been rubbed off and those are the contacting areas of the lugs. It is very important to check the headspace as you progress with the Go/No-Go gauges. A perfect 100% fit of the lugs is often unattainable but from my reading, 70-80% fit overall is fine.

Below is my experience lapping the lugs. None of what I show is new. It is discussed in other topics but I have never found it shown with pictures, so this is my tutorial.

CAUTIONS
-NEVER force the bolt to close on a gauge. Use minimal pressure and if the bolt doesn’t close on a Go gauge, the headspace is not right.
-As stated above, lapping increases headspace so as you progress, check headspace with your gauges. Once headspace is increased, it’s really hard to reverse it. Too large of a headspace (not passing No-Go gauge) can be dangerous to fire.
-In most cases, you do not want to lap the bevel of the bolt lugs (shown by the red arrows below in Figures 3 and 4). As you move the bolt up/down, you’ll be able to gauge where the bevel starts. Stay away from lapping this area.

Image
Fig. 3
fig3.jpg
Image
Fig. 4
fig4.jpg
THE MATERIALS (Figure 5)
-Lapping Compound (I use Clover 320grit; considered valve lapping grade)
-A Non-permanent Layout Dye (I use Dykem) and Black Magic Marker (I used one for this project and will explain that later)
-A Completely Stripped Bolt (removing extractor ring is optional, but recommended. I found that after I was finished, I had lapping compound in the groove and had to remove the ring anyhow to clean it.)
-A Spring Loaded Jig to keep rearward pressure on the bolt during lapping. (Explained below)
-Go and No-Go Gauges for your specific caliber (not shown)

Image
Fig. 5
fig5.jpg
Last edited by 72 usmc on Tue Dec 11, 2018 8:04 pm, edited 2 times in total.
To old to fight and to old to run, a Jar head will just shoot and be done with you.

72 usmc
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Re: LAPLAPING THE LUGS OF A MAUSER BOLT ACTION RIFLE

#2 Post by 72 usmc » Tue Dec 11, 2018 7:55 pm

SPRING LOADED JIG
There are no specific measurements for this jig. Each caliber will be different. You’ll notice the body is longer than the shoulder/neck. This is so the body still rides inside the chamber when not compressed; otherwise, the edge of the body will catch on the breech and cause a jam. For this jig, I used two spent cases, a Mosin-Nagant firing pin spring and some wood dowel to plug the neck of the case (not shown).

First, FL size your cases to get a nice fit in the chamber. Next, cut the cases. I used a pipe cutter for this and chamfered the cut edges inside and out with the Lee Neck Chamfer Tool. The pipe cutter gave a nice clean cut and didn’t deform the case. The chamfering is necessary so the case does not stick in the chamber. (Figure 6-7) Not shown here, but necessary, plug the neck of the jig so it can be pushed out with a cleaning rod. If that portion gets stuck in the chamber, it is very hard to remove otherwise (believe me, I know!!!)

Image
Fig. 6- Use Vise Grips to grasp/turn the unwanted part
fig6.jpg
Image
Fig. 7- Jig’s case compared to uncut case
fig7.jpg
Lastly, cut the spring. For this chamber and this round at 55mm, I found the spring cut at 55mm gave good back pressure on the bolt. (Figure 8.) And, there you have it, the final Jig. (Figure 9)

Image
Fig. 8
fig8.jpg

Image
Fig. 9
fig 9.jpg
PROGRESS
The next series of photos show my progress. Figures 10-12 show the progress after 120 strokes (up/down=one stroke). You will need to clean the lapping compound from all lugs and bolt before checking with dye and gauges. Also, clean the dye off before lapping again. This is the most time-consuming part. Figures 13-15 show the progress after 240 strokes. And Figures 16-18 show the final end results after 440 strokes. I stopped when I got the bolt to close nice and snug on the go guage. No force applied, just a solid close of the bolt. As should be, the bolt never budged on the No-Go gauge. I did not know how fast the lapping process would go, so I stopped after every 60 or so strokes to clean up, check headspace and recheck bolt lug fit. All told, I spent two evenings for about 3 hours each lapping. Notice in Figures 16-17 I switched to using a black “Sharpie” magic marker to color the lugs. This is because as I neared the end, the lugs were too smooth to rub off the bluing dye. The marker, however, did the trick. Also note that the dye wear didn’t progress as you would think it should. This is why it is best to back it up with the headspace gauges and check often.

Image Image
Fig. 10
fig10.jpg
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-----------------------------------------------------------------------------Fig. 11 missing from original Wayback
To old to fight and to old to run, a Jar head will just shoot and be done with you.

72 usmc
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Re: LAPLAPING THE LUGS OF A MAUSER BOLT ACTION RIFLE

#3 Post by 72 usmc » Tue Dec 11, 2018 7:58 pm

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Fig. 12
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Fig. 13-----------------------------------------------------------------------------Fig. 14
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fig14.jpg
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Fig. 15
fig15.jpg
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To old to fight and to old to run, a Jar head will just shoot and be done with you.

72 usmc
Firearm Fanatic
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Posts: 1792
Joined: Fri Jun 02, 2017 10:28 pm
Age: 67
Location: Menomonee Falls, Wi
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Re: LAPLAPING THE LUGS OF A MAUSER BOLT ACTION RIFLE

#4 Post by 72 usmc » Tue Dec 11, 2018 8:00 pm

Image Image
Fig. 16-----------------------------------------------------------------------------Fig. 17
fig16.jpg
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fig 17.jpg
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Fig. 18
fig18.jpg
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THE MESS
This is only ½ the cleaning patches I used. (Figure 19) Note the Denatured Alcohol. I used it to clean the dye off the lugs. As a final note, make sure you thoroughly clean the receiver and bolt (all nooks and crannies) of the lapping compound. Pay special attention to the chamber and inside the receiver. You don’t want to continue lapping further.

Image
Fig. 19
fig19.jpg
Go slow, clean thoroughly and check often. Lapping the bolt lugs of a Mauser rifle isn’t hard, but it does take some patience and time. Good Luck!!

metzgeri

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Words to Live by: "Proper Planning Prevents Pi$$ Poor Performance"
Words to die by: "Arbeit Macht Frei" and "Molon Labe"


Last edited by metzgeri on Fri May 15, 2009 2:09 pm, edited 1 time in total.
To old to fight and to old to run, a Jar head will just shoot and be done with you.

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