I have been studying the various custom actions available, and the machining processes use in their production, and a thought occurred to me.
This is a bit of a long stretch of the imagination, but heck, here goes...
Why hasn't anyone produced an integral one peice barrelled reciever?
Seriously, all of the disadvantages of the design are on the production side, and the advantage such a layout would have in strength and trueness would be worth that trade IMHO
Yes, there are some complications. Namely, the chamber will require some fairly complicated custom tooling and machinery to get it reamed and headspaced properly, but such tooling can be made, it's just that doone has done it yet.
As an extension to this idea, I have long been of the opinion that the bore can be handlapped after chambering by modifying the order in which certain processes are done. For a moment, picture this:
The barrel is gun drilled, but not rifled. Next comes the heat treat. Finally, the gun drilled hole is polished to final dimension for the lands. Next, the chamber is reamed BEFORE RIFLING. A chamber plug, drilled, heat treated, and polished to match the bore exactly can be threaded onto the barrel, occupying the entirety of the chamber. This extension allows you to cut rifle the length of the chamber (at least) behind the neck. The reason for this is you can then, after rifling, hand lap the barrel and not worry about "funnelling" at the stop point, as that stop point is in the chamber plug.
The advantage to this is you can hand lap the reamer marks left at the throat by chambering at the same time as you lap the bore. Cut off the traditional 1" from the muzzel, unscrew your chamber plug (which is now scrap metal, as it's a one time use only thing)and you have a hand lapped barrel with no remer marks in the throat!
These ideas could very easily be combined. Also, some custom makers include a scope rail on the top of their actions. I would like to see more of this, as all togther, you would have a rather superior platform for building a hell of a rifle! It has always been my opinion that the more different mechanical joints (screwes, threads, pins, stc.) can be eliminated, the more consistant and precise the overall package. Imagine it, reciever, barrel, and scope rail, all once peice, guaranteed true, square, and straight!
The one non production disadvantage I can see is the eventual problem of barrel wear. However, when the time comes, the integral barrel can be cut off, the reciever face polished square, and the tennon threaded to accept a more traditional barrel installation!
I must, for a moment consider the cost. This is probably the real reason it hasn't been done. All that custom tooling and exotic processing would mean it would be a costly setup. $3,000.00 or so would be my guess.
Considering people pay much more for that for some of the "custom shop" factory rifles (like the sub moa weatherby's) I don't really see that as too terribly much of an obstacle.
If any of you out there are entrepenurial enough to build or extend a buisiness with these ideas, I give you full locense to do so. I want no money or patend on them, as it would be of a good deal of benefit to the community as a whole, and right now I am without the means to pursue it myself. I would ask that if someone does develop this, a few units be sent my way as a thank you, but that's all.
Good questions. As I pointed out the real disadvantages are on the production side. With some of the rediculous lengths people have gone to in the past to achive a marginal increase in performance, this just seemed to me to be an idea long since overdue.
With the minute and precise capabilities of modern CNC and EDM machining, and a bit of out of the box thinking, I really feel that there's an idea to be had here. Maybe the time for it hasn't come yet, bit it will.
Heck, even if you have to come in at the back end and create a modified machine not unlike what is used for single point cut rifling, the recesses for locking lugs could be cut in from behind if you have a full body bolt diameter like the weatherby actions.
Yes, there are a thousand problems, big and little that make the idea wholly impractical.
Of course, they said the very same thing about repeating rifles about a year before they became the only thing to own...
While I'm at it, instead of integral rail or dovetail for mounting scope rings, skip the mount entirely, and make the bottom half of the rings integral! One more mechanical joint eliminated. One more tolerance meeting tolerance stack removed from the equasion!
I think you would have to show in the end that a one piece setup would be straighter with regards to the action/barrel than a tradition two piece setup. I think you have to find a different kind of interface between the bolt and the action to eliminate the alignment problems we see now. There would be problems lapping anything without cutting the ends off afterword. The lapping produces a bell shaped hole on each end. The chambering could be done with a plunge style EDM with an electrode long enough to reach through the action section. I know there are people cutting chambers with edm's now. I just don't know if you would be emilinating one of the causes off lost accuracy. It would be nice to see more actions with integrated bases at least. Have a good one.
Typically, the tolerances for runout and out of square are held to under 5 ten thousanths... rediculously precise, and there is nothing WRONG with this.
However, bear in mind that the tolerance applies to the action AND the barrel. In a worst case scenario, that means that a barrel that just makes tolerance fitted to an action that just makes tolerance could add up to 1 one thousanth runout AND one one thousanth out of square!
In a one peice setup, with the same tolerance level, the best case scenario is no better, but the worst case scenario is twice as good! What I'm really exploring is the upper end of quality control and consistancy in production.
Further, this would be a much stronger setup. Weatherby, for example made great claims about the strength of their "three rings of steel" ensrhouding the head of a cartridge. With good reason, it's a very strong setup. However, it isn't as strong as one ring of steel with a diameter equal to the aggregate diameters of those three, the mechanical joint between reciever and barrel is a weakness in the design that was neccessary only because of older machining capabilities.
As far as lapping without cutting off the end, please re-read above a bit more slowly. The bell shaped area where the lap is reversed would be contained in the disposable chamber plug designed for just this purpose, leaving the rifling, chamber, and throat fully intact. As stated above, the lapping plug would be useless after one use. Quite an expensive peice of tooling for a disposable unit! That is just one of the reasons the idea is impractical. The whole reason I came up with it in the first place is because it is the impractical that pushes design forward!
The remington three rings of steel would just be two rings of steel. It would be a little stronger because of the loss of the thread joint between the barrel and the receiver but you still have the inner ring......the bolt. The weak point then just becomes the recessed ring that is cut to allow the locking lugs to turn in. It would also be a challenge to drill the bolt hole in the action itself. Do you drill/machine it as straight as possible or follow the hole that was drilled for the bore section of the barrel? It would also eliminate the possibility of using a wire EDM to cut the bolt raceways.
I would go with a full bodied bolt with a recessed head, locking lugs the same diameter as the bolt body, very similar to the weatherby mark v. This way, the reciever could be drilled as concentric with the bore as possible, and polished out to final diameter. As added insurance, I would leave very minimal clearance between the bolt body and the reciever, and I would gas nitride them both to prevent galling. As near as I can tell, it should be possible to gas nitride these areas, while masking off the bore.
Bear in mind that this hole has to be drilled so the chamber can be cut, although if the chamber can be edm cut, that would be preferrable, so a reamer that bloody long dosn't have the chance to chatter and ruin the whole mess!