I recently bought the Mauser videos that you made and have a couple of questions for you.
First, in the video, you suggested lapping the lugs to where all three lugs were bearing. My question is would this induce bad accuracy since the third lug bears only on the bottom of the receiver and would cause a bind in the bolt somehow? The reason I ask is that I have heard through the years to always make sure the bolt doesn’t touch since this will cause vibrations that can cause erratic accuracy. Just curious as to what your thoughts are on this.
Second, in the video, the receiver you were machining did not look like it was turning concentric. I noticed that you did not run a tap into the threads to make sure they were concentric either, could this be a reason for that. The reason I ask is that from the other videos on doing receiver work, Mr. Holland always uses the tap to make sure the threads are concentric before doing the machine work on the front shoulder of the receiver. I may be wrong about it, but to me if the receiver threads aren’t concentric to the receiver, then the work you did on the barrel and receiver wouldn’t make much difference if this isn’t done first. Also, when you used the dial calipers to check the barrel shoulder, you came up with different measurements. Why would you not take the time to machine them to make them equal? It just seems to me that tightening the barrel up snug to the shoulder that isn’t machined would cause erratic vibrations as well. The reason I ask about this is that I plan to do a build and machine the shoulder so as to make it fit perfectly. Would you think this is a waste of time or should I not machine it at all due to some other reason?
I would appreciate any information you can share with me on this. I know you didn’t say you were trying to make the rifle shoot as accurate as you could and this may very well be the reason you didn’t do what I was asking about. If you rebarrel a rifle though, shouldn’t that be your goal? Thanks.
OK the third safety lug contacting is contacting as well as the front two lugs. When the round is fired the whole bolt takes the rearward thrust, there would not be any bind on the bolt. There would if only the rear lug was touching or if only one of the front lugs and the rear lug were touching. The third lug touching will not be the cause of bad accuracy. We have built multiple Mauser 98 rifles with the safety lug contacting and the accuracy was/is very good. The reason for the safety lug to contact is safety. As I mentioned in the video when that lug is contacting the strength of the system is increased by one third.
Now as far as the threads being concentric, the action mandrel fits thru the whole receiver where the bolt rides. When the face of the receiver is trued to that surface the barrel will tighten down even with that surface. The barrel will be in line with the bolt. That is why we use a mandrel thru the receiver. If the threads were off to where it would make a difference the mandrel would not screw into the receiver, the back would bind in the receiver, then the threads would have to be trued to the bolt position. The bolt face on Mausers are always a bit oversized so the cartridge will fit in the barrel and not bind on the bolt face. The reason the measurements from the front of the receiver varied have to do with the inner ring. They are never true and by the receiver threads are often rounded or some even have a small step in them. Again I don’t true up that shoulder as there is no real reason to. The barrel shoulder needs to touch that surface to insure as much of the cartridge case is supported in the barrel as possible. If the barrel touches that shoulder and not the face of the receivers then you would have problems. There is a tap on the market to re-tap or fresh out Mauser threads, this tap will follow along the same line as the original tap when the receiver was manufactured, so you would end up with the same problem if the threads are off so bad the barrel fits crooked in the receiver. I do not know of anyone who makes a tap with a guide that fits in the receiver like they have for the Remington 700’s. I have seen one Mauser that had the problem you describe and the fix was a very lengthy process of fitting the receiver in the 4 jaw chuck of the lathe and truing the receiver off of the bolt raceway. Then re-machine the threads on the lathe. When we build a rifle we try to do all that we can for accuracy. Much of what we did will help with accuracy as well as make the gun stronger and safer. If you are concerned with the receiver threads on your gun look at the original barrel, (before you pull it off), if it sits crooked you might have to really look into why it is crooked. Again I have found that it is usually the face of the receiver is not true so when the barrel is tightened down one side touches and the barrel is pushed one way or the other making it appear as though the barrel is crooked in the receiver. That is why we always true the receiver face. If you have just an action with out a barrel and you are concerned about this potential problem you may want to take an old barrel or a piece of steel and thread it and fit it up to the receiver and see how it fits. Then if it fits crooked figure out why it is crooked first and address that problem. Great questions, hope this answers them. Ken.
Reply:
Thanks for the quick reply and very helpful answers. When I was talking with an older smith that I know, he questioned me on why the safety lug was brought into bearing and his reply was along the lines that it didn’t need to bear and if it did the Germans or whoever made it would have done so at that time. Had me second guessing the reasoning behind the safety. I am glad to hear that you haven’t had any accuracy problems with it.
The explanation dealing with concentricity makes sense to me as you explained it. As to dealing with the threads, would you recommend me not worrying about chasing the threads unless I had trouble threading the barrel on? I have run into a couple that gave me trouble with binding and the tap chased the thread and made it tighten up without a problem.
One last question and I’ll let you go on the matter. If I machine the inner ring and then have the receiver heat treated, would you think this would cause me any problems down the road? I may be a little anal about the details, but I want everything to be as perfect as possible within reasoning.
Reply:
The safety lug bearing only has to do with making the gun stronger. If only the front two lugs touch and not the rear, and an overload occurs and the front two lugs let go the third is supposed to come into contact and stop the set back. If there is an overload and the front two lugs let go the third isn’t going to stop the bolt. It will slow it down some. With the third lug touching right from the start the whole system is stronger and will take more pressure before the gun gives up the ghost.
Chasing the threads is not a bad idea, I don’t because I fit the barrel to thread in and snug up as it comes into contact with the inner ring. The threads in the receiver have a slight taper to them as they were cut originally with a tap so they will seem loose at first then get tighter as you go. If you have had good luck with re-tapping the receiver then by all means go ahead.
As far as machining the inner ring, go ahead BUT make sure that when the bolt is inserted and locked up that the bolt and the two protrusions that are on each side of the ejector slot, do NOT extend forward past the inner ring. We want the barrel to extend as far back toward the bolt as possible so the cartridge is encased in as much of the barrel as possible. If the bolt and the two protrusions extend beyond the face of the inner ring you will have to move the bolt back and that means you are decreasing the amount of locking lugs you have. Or you will have to machine an area into the back of the barrel for the bolt or protrusions to fit when the bolt is closed. This is a pain and unnecessary.
