Month: January 2005

Tight Barrels

Posted by on January 23, 2005

I love this sort of technical discussion, it’s how we improve our knowledge. First off, I don’t think Barry’s remark about idiots fooling with guns was meant to suggest that we’re all incompetent, rather that there are indeed a few idiots that need to be saved from themselves, and that might well be why barrels are so tight, well beyond the degree of tightness needed for safety. If it emerges as a result of discussion and experiment hat barrels can safely be fitted less tightly it will be an important step towards the sort of home gunmaking that might be necessary in future.As for Gary and Brett’s comments about professional gunsmiths, I have uncovered a stack of similar stories from reliable sources, and I too have fixed guns that were butchered by some of these charletons.Gary’s story about plating was interesting. In the last few months I have seen three electroless nickel plated pistols that were corroding under the nickel. It seems that most metals including nickel are porous to some extent and that moisture can penetrate. The nickel was not actually peeling from any of these guns but the corrosion was clearly visible. All were carry guns worn on the right and all the corrosion was on the left side of each gun, obviously from perspiration. Although electroless nickel is a better and harder finish than the electro variety the problem is stripping it if you need to. Electro plating can be stripped by reversing the process but electroless can’t. Brownells has a safe and easy chemical stripper but won’t export it. The only other method I know of involves cyanide. Basically therefore, once you’ve electroless nickelled a gun you’re stuck with it, and if corrosion starts there’s no way to stop it. Hence my preference for old fashioned blueing. Less durable but light corrosion can be polished out and blued about as often as necessary. Can be done at home at minimal cost.Brett’s comments about the 98 raise interesting points. Truing the receiver ring and internal shoulder is desirable for accuracy provided the possible consequences are understood. 98s were all made from a low carbon steel and case hardened. In some cases, depending where and when they were made, the case is very thin, sometimes as little as five thousandths. Truing the internal shoulder on a lathe would be likely to cut through the case. Such truing is best done by hand with a tool that can be made, and is basically a lapping job. Even then Jerry Kuhnhausen recommends re heat treatment afterwards because of the risk of thinning the case too much. Same goes for truing the receiver ring for the same reason. I set them up on a mandrel in my accurate lathe and check the receiver ring with a DTI. That shows how much out it is. If it’s very slight a little lapping will true it or almost true it without taking off more than a thou or two which can safely be done. If it’s more than that, you can take of the same one or two thou but no more unless you are prepared to have it re heat treated.The matter of how a 98 barrel should be fitted is simple enough provided you take the trouble to understand the principles. What distinguishes the 98 is it’s internal shoulder. That is the primary tightening shoulder. The receiver ring is the secondary shoulder. That is apparent on all the actions I’ve seen. The tight engagement of the barrel could be seen in the slight depression it had left in the face of the internal shoulder. The idea is to machine the barrel shank to the same length as the depth between the receiver ring and the internal shoulder so that the barrel face and shoulder both tighten up equally. A refinement is to make the barrel shank one thou longer so that tightening is slightly more on the internal shoulder.Is it important ? I can’t say, but I can’t see why it should be. After all, if the barrel shank is left slightly short you’d have the same situation that you have on all other bolt actions, so I can’t see that it would be a problem. But, as the internal shoulder is there, it makes sense to cut the barrel shank to fit the action in accordance with standard practice.Barrel threading and chambering is straightforward if you’re doing it yourself. The best bet for most amateurs, however, is to buy a barrel profiled, threaded and chambered. For one thing profiling is a lot of work, and what people like Truvelo charge for doing those things is so reasonable it’s not worth doing them yourself. Ideally, threading is best done to fit the individual action, but the one we’re now working on was prethreaded and seems very accurate despite the barrel and action threads being a slightly loose fit.Chambering is where it gets interesting. As far as prechambering is concerned there are two ways to go. You order it long or short chambered, about half a millimetre long or short. It should be remembered that it is impossible to chamber to the correct headspace without the action. A long or deep chamber is cut a little deeper than neccessary. The barrel face and shoulder are then trimmed back a thou at a time on a lathe on a cut and try basis till the headspace is right. That’s the cheap and easy way.A short chamber, which is what we are doing right now, is cut shorter by about half a millimetre. It is finished to the correct headspace with a finishing reamer by hand using a tap wrench, a thou or so at a time until headspace is right. A chamber reamer costs about R1000 which is the disadvantage if you’re cutting only one chamber. Both methods need a lathe for trimming the barrel shank to fit the receiver.Both also need headspace gauges. Those are not expensive at R300 a pair, and the go gauge is sufficient on it’s own.Chambering and headspacing is easy and well within the ability of anyone with handyman skills and the necessary theoretical knowledge.BTW it’s interesting that Brett’s 98 that was heat treated again was made in 1944. Quality began to deteriorate from 1941 and was very poor in some factories by 1944. That would probably explain the need to re heat treat it. All 98s are now more than 50 years old. Most are well used. All should be approached with some circumspection. Generally though, those made before 1941 right back to pre WW1 are usually OK if they are visibly in good condition and haven’t been worked on by some incompetent who might have left them unsafe in certain respects. To those who are interested in the finer details of the 98 I strongly recommend Jerry Kuhnhausen’s ” The Mauser Bolt Actions.” The detail is extreme and exceeds everything I’ve got from all other sources combined.[Originally posted to SATalkGuns -- Admin]

Rifle Stocks

Posted by on January 2, 2005

In my amateur and professional gunsmithing work ( which has more or less come to an end with the FCA ) all sorts of ideas have occured to me, some of which have been tried, others not. In the latter category is an alternative method of stock making. This isn’t likely to appeal to many as a stock is about the last thing most DIY gunsmiths would need to make. But if one is needed there are easier ways to make them than the “standard” way of carving them out of a solid piece of walnut or other suitable wood.It is based on synthetic bedding. As a perfectionist I see the beauty of a precisely inletted stock. But those who have made them know what a ball aching struggle it is to inlet an action precisely, a couple of thou at a time with scrapers and inletting blue. Fact is there’s no point to it. The most precise inletting can’t equal synthetic bedding for close fit. Synthetic bedding is almost always done for accuracy, but it is also useful as a method of simplifying inletting. If more wood is going to be dug out, and none too precisely at that, to make way for synthetic bedding, why bother doing it so precisely in the first place ?Of course, when talking about short cuts we’re not talking about exhibition grade stocks, we’re talking about practical working rifles. There are two routes to go. The first is to cut out the inletting with a router using easily made guides and templates. The router bit is simply set to the required depth. The shape of the inletting can be done in a series of steps, as there’s no need for the rounded surfaces as they will be filled with expoxy. It’s a bit less simple at the tang which needs to be cut fairly precisely for appearance, but in general the whole procedure is a lot quicker and easier.The second method is laminated stocks. The purpose of laminated stocks is to get a degree of stability, ie resistance to warping, better than can be expected with conventional stocks. But there’s another advantage. If a stock is made up from thin laminations, say 3 to 6mm thick, the laminations can be cut to shape before glueing. If those cuts are carefully calculated, the inletting will be in place after glueing, no further cutting required. The calcs and the cutting are a bit slow and painstaking so it will appeal only to those who don’t want to buy a router, but it works very well.Another perhaps minor advantage is that lesser quality wood can be used for laminated stocks. A good walnut blank is nothing less tha R1000 these days. By good quality I mean plain wood without much figure but hard and close grained and properly seasoned. Figured wood is more expensive. American walnut can be obtained more cheaply in grades that would not ordinarily make a good stock. Other woods are also available such as beech, birch and maple. But they will make good stocks if laminated.Laminating is not difficult. Just a matter of sawing the blank into thin slices, running them through a planer, reversing the direction of each alternate slice, and glueing them together. The type of glue needs some investigation. It needs to be impervious to fungal attack or moisture. I used ordinary wood glue for my experiments but I think something better is needed for a proper job. Right now I can’t say what it would be.It’s not a good idea to laminate the whole stock in one go. That could be as many as 15 laminations. I reckon it’s best not to glue more than three or four at a time, but I could be wrong. A piece of laminated construction timber makes an adequate base for laminating, but those who want something better could use a piece of rolled steel channel. Clamping is by G clamp or wood and screw clamps that can easily be made.This is hardly a complete explanation. I haven’t tested it far enough to offer more. But I’m satisfied that either method will work well for anyone willing to try them.[Originally posted to SATalkGuns -- Admin]