Some years ago, I had a gunsmith install a 7 x57 barrel on a G33-40 action. I
I presume, but don’t know if he lapped the lugs in. He had a good reputation. After, I sent it to Blanchards for heat treating. Probably not a good move, but since the action had been surface ground, I thought it may harden the surfaces for smooth operation. The barreled action sat for years and in another flight of fantasy, I decided that it should be a 280. Off goes the old barrel and I order a Brux barrel. Since, the original gunsmith had passed, I took it to a new gunsmith to be Re-barreled. As part of his normal barreling procedure, he laps the lugs. After he barrels the action and when I picked it up, he says that one of the lugs was ten thousands off and it took quite a bit to lap it in. He thought the action may be warped a little, but went ahead and barreled it.

I got to thinking about this and have laid a straight edge along the bottom of the action and it appears to be perfectly flat. Yet, I started thinking if he took 10 thousands off and it would have come off the lug seat, would the lug seat surface be soft allowing for lug set-back. I haven’t shot the gun, but started wondering if I should send the action back to Blanchards to get it re-heat treated.

Any advice would be appreciated.

First of all I would have a qualified gunsmith pull the barrel and measure how much has been lapped off it.
I’d be very reluctant to send it back for another re-carb.

Check the action on a Rockwell Hardness Tester. Then you know.

Lapping lugs by pulling back on the bolt handle will give uneven lugs. I use a jig that pushes back on the bolt face for even lug lapping.





If the face of the action has been trued properly, you can measure each lug using a depth micrometer.

Same say lapping lugs on an old Mauser removes the case hardening on the lugs. Likely a true statement. Time for DPCD to enter and state his opinion.

The way to tell if an action has been warped is to screw a facing mandrel into the action from the front. It won't go into a warped action. You will have to pull the barrel to do this.

Yep.

[QUOTE]Originally posted by WoodHunter:

If the face of the action has been trued properly, you can measure each lug using a depth micrometer.

Won’t the C-Ring get in the way?

.010 is a lot.
If that receiver was warped enough to put one seat ahead of the other by .010 you'd never get the bolt in it all the way.
Something else is going on there.

Thanks for replies. The bolt moves back and forth as smooth as glass. It also closes just find. I’ve used head space gauges and the headspace is fine.

From all outward and operational appearances everything appears fine.

Could there be a problem by re-heating the action. My thought, if everything is working fine and the lugs are properly fitted to the lugs, then I could just heat treat again and I would be good to go. But, I just know enough about this.

Timan, you got me thinking, so I called the gunsmith that lapped the lugs in. He’s an old timer and retired so I didn’t want to bother him, but he was fine. I was wrong about the amount. He said that one lug had to have about 2 thousands taken off. I don’t know if this changes anything

I have never seen a Mauser which had .010" clearance on a lug but I suppose it could happen. I don't think you could warp a receiver enough to create .010 without having the warpage be immediately obvious. I don't think he had to lap .010". So far as testing is concerned, it is difficult to get in and test the locking lug seats. In fact, given the mauser design, it's fairly difficult to get in to the seats to do any thing.
Unless I was absolutely certain the locking lug seats were screwed up and the lugs were not bearing, I would not touch the seats on a Mauser. If the action has been used much, chances are the surfaces mate pretty well. If the action has been re-treated, it's difficult to say what dimensional changes might have taken place.
I think there is more damage done to actions by guys trying to lap lugs than are ever improved by it.
I have a half dozen of my own rifles built on Mausers. All of them work well and I've not touch the lugs on any of them. I've barreled a few hundred or more and didn't lap them either. If there was any sign of set-back, I simply declined the job. Regards, Bill

At the risk of drawing fire from the Mauser haters, (who I expect to come on the net shortly), I have to say this;
There is nothing wrong with your action. The real test for a warped receiver is, does the bolt still work.
Use it as is. It is impossible to Rockwell test locking lug seats; testing the outside tells you nothing useful.
I have seen massive lug setback on the Spanish 93s that guys fired with 308s (much higher pressure than the 7.62 CETME). But never on a WW1 or later 98. Some 1908 Brazilian and 09 Argentine, yes.

quote:

Originally posted by metal:
[QUOTE]Originally posted by WoodHunter:

If the face of the action has been trued properly, you can measure each lug using a depth micrometer.

Won’t the C-Ring get in the way?

Darn, think my 74 year old brain had M700's and M70's in mind. I guess the assisted living facility is not far away.

quote:

Originally posted by dpcd:
At the risk of drawing fire from the Mauser haters, (who I expect to come on the net shortly), I have to say this;
There is nothing wrong with your action. The real test for a warped receiver is, does the bolt still work.
Use it as is. It is impossible to Rockwell test locking lug seats; testing the outside tells you nothing useful.
I have seen massive lug setback on the Spanish 93s that guys fired with 308s (much higher pressure than the 7.62 CETME). But never on a WW1 or later 98. Some 1908 Brazilian and 09 Argentine, yes.

True, true.

I had my doubts about the 0.010 also.

I crushed a 1909 years ago with an action wrench. Bolt would not go in all the way after removing the barrel. I made up a tight fitting mandrel that I now use on 98's, stick it up into the action before tightening the action wrench.

All those Mauser haters can send their actions to me.

I was thinking a Rockwell test would reveal if the action had actually gone through a recent heat treat. And, if the readings are taken just under the lug as shown, low numbers would indicate a soft lug.

BTW someone that knows tell me what type of Rockwell C numbers are obtained with a re heat treat on a M98.

There we go again, too much thinking on my part that may be in error. Getting old is hell!

I have seen setback on the 1908 Brazilian Mausers when they were loaded hot but never on the 1935 (Oberndorff) models.
The hardening done on many of the Mausers is fascinating, to me. In some, the locking lug seats are hard, the extraction cam surface is hard, and the rest is relatively soft. On others, the whole receiver is quite hard. The aforementioned 1908 DWM Mausers are relatively soft and easily deformed.
I kind of think, when a gunsmith speaks of the necessity to lap .010" to achieve full contact, especially on a mauser, he is likely blowing smoke. Regards, Bill

quote:

Originally posted by Bill Leeper:
I have seen setback on the 1908 Brazilian Mausers when they were loaded hot but never on the 1935 (Oberndorff) models.
The hardening done on many of the Mausers is fascinating, to me. In some, the locking lug seats are hard, the extraction cam surface is hard, and the rest is relatively soft. On others, the whole receiver is quite hard. The aforementioned 1908 DWM Mausers are relatively soft and easily deformed.
I kind of think, when a gunsmith speaks of the necessity to lap .010" to achieve full contact, especially on a mauser, he is likely blowing smoke. Regards, Bill

Well said!

quote:

Originally posted by Bill Leeper:
I have seen setback on the 1908 Brazilian Mausers when they were loaded hot but never on the 1935 (Oberndorff) models.
The hardening done on many of the Mausers is fascinating, to me. In some, the locking lug seats are hard, the extraction cam surface is hard, and the rest is relatively soft. On others, the whole receiver is quite hard. The aforementioned 1908 DWM Mausers are relatively soft and easily deformed.
I kind of think, when a gunsmith speaks of the necessity to lap .010" to achieve full contact, especially on a mauser, he is likely blowing smoke. Regards, Bill

I agree. Some of the M98 bolts I have put into the Wilson tester have been up to 37 on the Rockwell C scale.

I have a Corona action: Tests at Rockwell C 20 on the receiver, but the bolt is Rockwell C 53 on the bolt body just behind the lugs. Might be a heavy case.

Thanks for the input. I really appreciate this from those what they are talking about.

I’m not going to have it re-heated treated. I’m going to shoot it next week when I can get out on the range. If there are any problems, I’ll post it. Thanks again for the help

The G33-40 and the Brno mod 21 and 22 and the German Custom Service Mauser (mod 35??) are awesome small ring actions, and normally don't need to be reheat treated or so Ive been told, and Ive owned a number of each and made them cook in the high pressure loads..