Rifle Came Back From Machinist...Claw Mounts Crooked?

[mhutchinson]

Hey folks,
Been a while since I posted here. Been busy and my Honold Mauser project had to be set aside for a while but I finally got it back from the machinist/gunsmith. But to my distress I think they may have screwed up the claw mounts. Refer to my older threads for more pics of the rifle and the claw mounts that I found separately on that one auction site.

The shop I took the rifle to doesn't do much (if any) of this kind of work but they are a good, reputable machine shop that I have gone to before and they do plenty of work on newer firearms. Despite being smack in the middle of a gun-friendly state like Kansas there really aren't a lot of gunsmiths who work on old stuff like this anymore. If you mentioned something like a "guild gun" they'd probably ask you what kind of AR derivative that is. But that's another conversation.

Anyway, they had my rifle for quite a while because the machinist wanted to give some thought to how best to mount the scope before getting to work on it. He was reluctant to mill off the clip bridge because he thought he would have a tough time making the contour blend perfectly with the curve of the receiver. Odd, I thought, because my understanding was that milling off the clip bridge was a pretty standard operation. But whatever, he's the machinist, not me. He ended up deciding to grind off a corner of the rear mount to clear the bolt handle instead then ground off a little at the front of the mount to fit up against the clip bridge. Not as clean-looking as having the clip bridge ground off but I can live with it. Function over form. And I honestly don't know if there is anywhere in town that would take on this project other than these guys.
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Now here's where the problems start.
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I can tell with my naked eye that the front claw mount is not in line with the iron sights. I guess this might not be a problem in and of itself. Perhaps the iron sights are not square to the receiver in which case I'd rather have the scope mount square to the receiver than square to the iron sights, obviously. Anyway, I don't have the equipment to determine this myself since there isn't any easy, flat reference on the receiver.

And now here's a more legitimate concern:
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The two claw mount bases don't appear to be square to each other. Perhaps these old parts were hand-made and the surfaces were never perfect but I figured the top surfaces of the mount bases have to be pretty damn close, right?


Continued below...

[mhutchinson]

The case for the mounts being crooked is strengthened by the fact that with the scope rings tightened onto the scope, I can't get the front mount to release. First I attached the scope with the rings loose and made sure that the claw mounts were as well-seated as I could get them. The rings were loose enough that the scope could be moved around in the rings easily. Upon attaching the scope, it would no longer slide around in the rings so clearly there is some tension somewhere due to something being out of line. But at this point the front mount still released easily. When I tightened the scope rings a little, though, the front mount became stuck and would not budge.

Here's one potential issue:
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The rear mount doesn't fully seat into its base. It wouldn't do so when I got the mounts but I know these things are fitted very meticulously so I didn't want to mess with it. But as it is, if the claw is actually meant to seat more fully, then the scope ring would be canted up a little which would maybe explain the tension upon tightening the rings.

Should I do anything to get the claw to seat more fully other than make sure the parts are all clean from dirt and debris?

It seems to me like it would be reasonable to do this before going back to the machinist and concluding that the bases were mounted incorrectly...but I wanted to check with the council first lest I do any damage.

What sayeth you, o wise and prudent council? Did these guys botch the job?

On a related note, is there any way for me to accurately determine whether or not the relevant parts are squarely mounted? I do have a very accurate (Starrett) combination square, straight edge, and other basic tools.

[Steve Whitley]

Judging just from your photos, I am tempted to say "ouch" and let it go at that. The rear claw mount appears to be canted even further to the right. Hope you can have that corrected.
Steve

[mike ford]

mhutchinson,
The bases are not mounted squarely, as can be seen from the photos. The front ring doesn't fit the contour of the receiver( Military receiver rings are often different diameters, this doesn't affect it's use as a battle instrument. The front ring should be mounted so as to "clear" the base when it swings up and the arc of the "claws" has to have room to swing past the end of the slot. In the other thread, I described how to either mill or file the "clip bridge" off. This is a pretty common operation for anyone working on Mausers. To tell the truth, I was a little taken aback that the grinds were not finished/polished/ colored to match. The first thing you should do is loosen the front ring and move it back enough to swing out of the base. In doing this make sure the reticle is square with the rifle. Once this is done, take the rifle to the range and see how it groups with out taking it off. If it groups, take the scope off, remount it and see if it groups close to the same place. If it does, great. If it doesn't, sight it in again and use the mounts as "fixed" and don't remove them again. If you can't get it to group, at all, then there are other problems.
Mike

[mhutchinson]

Thanks for the replies, fellas.


As for the grinds not being finished, I told them to do that because I am gonna be re-bluing the rifle anyway and I can do the finish work myself. Just wanted to save some money by cutting down on the shop time.

I'm a little ways away from being able to shoot the rifle actually. There are some cracks in the stock that I need to fix first lest they become worse when the rifle is fired.

As for the rear mount, do you guys think it would be a bad idea for me to do some fine polishing so that it seats more fully into the base? After careful examination, I think that is part of what is causing the front ring to become stuck when I tighten the rings--with that rear ring not fully seated the mating surface between the ring and the scope is canted a little bit and when I tighten, it wants to pull the front of the scope up a little.

[mhutchinson]

Just looked back at that older thread, by the way, about milling off the clip bridge. The machinist's reluctance to do that was a bit of a red flag in my mind but I decided to trust his opinion because he's a machinist. Guess I made the wrong call there. Shoulda just milled it off myself.

[Diz]

From your photo's I agree that the bases are not square. There is a tool that looks like a pair of machined rods with points on the ends for checking the alignment of the mounts. You put these in the scope rings with the points facing and they should be point to point if everything is right. If you have enough clearance between the scope and the gun you may be able to refit things by careful filing but my thought is that the shop is responsible and anything you do will negate that. I would take it back and show them what is wrong and see what they say before trying anything. Diz

[don't]

I would be cautious taking it back to the same machinist myself as they may make things worse trying to "fix" their mistake. Between machinists and gunsmiths I could write a book on the things they either screwed up or could not do. I know not all of them are like this & I know there are still some true craftsman (read as can think thru a problem and take pride in their work)... If you find a good one you are lucky...

Good Luck..
Don T

[mike ford]

mhutchinson,
Do not do any "fine polishing" on the mating surfaces of the rear base/rings, they have already been fitted to each other. If you are "bound and determined" to do something, then you should scrape the bases so they fit the rifle's contours and are square to it. The tool Diz described will show you if the bases are the same height as each other. To check if they are square with each other, you only need two "sticks" of "key stock". They don't have to be the same size. You place one of them cross wise on a trusted square surface. Then place the other, cross wise, on top of one of the bases. Then step back and sight across both pieces of key stock. You may have to squat down to get on the same ( or similar) plane as the key stock. It is amazing how small a deviation can be detected by this method. When you sight across the two pieces, what you are looking for is how parallel the two key stock pieces are, not the difference in height. Different "true" or "trusted" surfaces can be used, such as the flat top of a front sight base, or rear sight base, or a previously squared scope base. If you can't find anything else, you can clamp it crosswise to the flat bottom of the action. Pick one of the bases and fit it to the contour of the action, and in doing so, square it up. Now, here is the tricky part. To do this, you place a spotting compound( Prussian Blue, smoke, lipstick, etc.) on the receiver and transfer the high points to the part being fitted. The fitting is done by scraping the high points identified by transfer of the spotting compound. This is where you can "mess" the parts up so badly you "can't sell them for scrap iron"( a joke). This type scraping is entirely different than what you will find if you check You Tube to see how to do it. They will be working on flat machine surfaces and you will be working on curved surfaces with varying radii. In the case of your rifle it is extremely important to place the part being fitted onto the rifle in the same place every time you "spot it in". If you don't, you will not get a true spotting of high points and can scrape the part to "nothing", and still not have it fitted. To have acceptable results, you can drop the part onto the receiver over headless 6-48 screws turned into the mounting screw holes. This will keep the same part in the same place every time. You can make a scraper from a three corner file by carefully grinding the teeth off and sharpening the three corners( a handle is necessary). The motions required in this type scraping are "circular"( for want of a better word) rather than "flat". It is more akin to scraping bearings than anything else. It is very hard to learn this by reading a description, it is much better to watch someone else do it. If you insist on doing this, I suggest you make up a blank base and practice scraping on it before the actual bases. Once you get both bases fit up, reinstall the scope and see how it works. A major disadvantage to the "drill" you are going through is you have to worry about both the bottom and top surfaces. When a traditional set of claw mounts is fit up, say on a drilling, the bases are fit on the bottom surfaces to the barrels, soldered to the barrels, and then milled on the top surfaces of the bases and dovetails, in the same set up. This insures everything is level and parallel. If you have questions, I will try to answer them.
Mike

[Tom H.]

I completely agree with Mike about not taking any metal off the claws or they fit into the bases. One of the first things I would do is see if the front base was true to the bottom flat on the action. That would tell you if that one was installed correctly or not. If it is then that's fine if not that's another issue entirely. In order to get the rear base parallel and true with the front base I would take the screws out and run a block that you know is true across the front and the rear try to keep it in the same place and see if the holes line up in the back.
The rear might not be off too much so if you had to you could redrill to 8:40 as long as you had a mill to do it with retap and have a rear sight base that aligns.
Good luck, Tom

[Tom H.]

Depending how tight the barrel already is to the action you could always put it in the vice and loosen it a tiny bit more to get it to align with that front base. There's only a tiny fraction of a turn that would allow you to do that and it would have no effect on headspace

[mike ford]

Tom H.,
Both bases are attached to the receiver, turning the barrel wouldn't change the alignment between the bases. To line them up, you have to scrape the high points, to bring it level. It's a slow process. If one base is too high, that is a different problem, that can be dealt with if it comes up. I wouldn't change to 8-40 screws.
Mike

[Diz]

Mike said scrape and I said file, both will get you there if you are careful and that is the operative word. Very careful is more like it because once you remove the metal it gets a lot harder to put it back. I agree with Mike on the screws, change them as a last resort.

Being a gunsmith or machinist puts a person in an awkward position if they make a mistake. If they are ethical and responsible they will do everything possible to correct it. I would at least talk it over with them. Good luck with it.

Diz

[Tom H.]

Hello Mike, perhaps what I said was misunderstood. If the front base is on correctly the barrel can be turned to align the site with the front base as it only looks like a very small fraction of a turn is needed. This should have virtually no effect on headspace as long as the shoulder of the barrel is still tight against the receiver. If the rear base is crooked it may be possible to file one side of it down so that it will become a level with the front base but if the holes are off too far it may be beneficial to either weld the holes up And re drill or to realign and redrill with a larger screw which should clean the old holes up as well.

[mike ford]

Tom H.,
The importance of the barrel and front sight base is that it predated the scope mounts we are concerned with here. Consequently, we can trust the flat thereon as a true surface. Instead of turning the sight base we trust to match the scope mount base we don't trust, it is better to adjust the scope mount base to level it in comparison to the trusted surface. I prefer scraping to accomplish this, because that is the way I learned and we are dealing with curved surfaces. I understand some people may be more comfortable filing. Whoever is doing the work should use the procedure they believe will have the best chance of success. I have some experience with misplaced holes, but we don't know yet that any are misaligned. If we find one, we can deal with it then.
Mike