Rifle assembly

Discussion in 'Long Range Hunting & Shooting' started by rossneder, Dec 29, 2006.

  1. rossneder

    rossneder Active Member

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    I'm in the process of obtaining a 338 Lapua for long range lead delivery.

    I love the Sako TRG 42 but have a hard time with the cost.
    In researching this it seems like it would not be to hard to assemble some well made parts and have an equivalent gun for significantly less.

    I'm thinking of an AI stock, the new Predator XP action, Shilen select barrel, Jewel trigger and the misc minor components all based on the Rem 700 parts.

    The action comes ready to go, the barrel can be ordered chambered and threaded on both ends, trigger is drop in as is the stock.

    So what am I missing, where does the gunsmiths artful ability come in that adds a considerable expense to an already accurate gun?

    Clearly I will need to develop loads, but is there something else that would make this hard?

    Thanks,
    Ross
     
  2. murf

    murf Well-Known Member

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    Ross,

    There are a few smiths on this board that could probably answer your question much better than I, but I'll take a stab. A rifle is a precision instrument and every piece has to fit and function precisely for safetys sake, let alone accuracy. I am a machinist by trade and still to this day have never built my own gun. Like any trade, there are techniques and knowledge that are only acquired by years of hard work, love and dedication for the task at hand and rifle smithing is definately one of those trades. It may seem expensive to have a top notch smith like the few here on the forum build you a shooting stick, but piece of mind knowing it's done right in the end is all I need. By all means you could probably do it yourself, there's no better experience than just plain getting your hands dirty and doing it, but remember safety should be your #1 priority. Accuracy would be #2.


    Murf
     

  3. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Ross,

    I have built a few rifles that are working pretty well at long range and will tell you there is no rocket science to doing it. BUT, what it does take is fine attention to detail to make everything absolutely as near perfect as we can get them to get the most consistancy at long range.

    I have never seen a Shilen barrel set up for a Rem 700 that was prechambered and threaded in the 338 Lapua chambering. That aside, a properly built full custom rifle shoots so well simply because every part of that rifle is hand machined and fitted for perfect fit and alignemt. Again, not rocket science but every custom rifle is built with one goal in mind from the time you get the componants in shop until you tighten that last receiver screw on the finished rifle, perfection!!

    Now, your receiver choice is a good one and from what I hear yes they are ready to build on right out of the box.

    From there though, I would have to steer you away from a pre fit Shilen. Spend some extra money and get a world class barrel, Lilja, Rock, Krieger, Lawton, Broughton, Hart. Any of these will get you world class performance if fitted properly.

    Fitting properly means that when your cutting the receiver threads, you go from the barrel threading into the receiver in a 1/2 thou cut pass. Before the cut it will not fit, after the 1/2 thou cut pass it will.

    That takes time and the desire to make it as quality as you can.

    Then the desire to strive for perfection also comes in the tooling used to machine the barrel from live piloted center cutters to set up the barrel for machining to live piloted chambering reamers and crowning tools and the vast selection of varying bushing sizes to get that perfect bushing to bore fit, not just close enough.

    These tools are expensive but the only way to do it right, I suspect the prefit shilen will not be machined with these tools and there is no way the threads will be as quality fit as they should be for extreme accuracy in a finished rifle.

    The larger the chambering the more stress is applied to the rifle system when fired. The more stree, the more the flaws in the rifle will show up down range. A big rifle like a 338 Lapua need the best componants and fit to get extreme accuracy.

    Its easy to build a 308 Win to shoot 1/2 moa or less. YOu need as close to perfection to get a 338 Lapua to shoot to this level of consistancy or better.

    Mainly what you are missing in your project is the desire and experience to built that "perfect" rifle. No rifle is perfect but for me and many other smiths on this board, that is our goal everytime we start a rifle project.

    Thats what you get for your considerable expense.

    Ya ever heard the phrase "been there done that" Well, you may well get all your componants and assemble them and you may well get a fine shooting rifle but it is at least as likely you will get a rifle that will shoot no better then most factory rifles. Its a crap shoot. If it shoots great, if not, you spent all this money and will have to spend alot more to really get what you want and in the end you may well end up spending much more then you would have if you just ordered a full custom rifle from an experienced smith that knew how to build a rifle to meet your goals.

    Good Shooting!!

    Kirby Allen(50)
     
  4. rossneder

    rossneder Active Member

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    Thanks Kirby and Murf,

    I kinda live in my shop and have been fabricating for 30 years, hence my abundant confidence. On the other hand I have spent thousands to make a hundred dollar part along with the huge time investment.

    If I'm reading correctly, setting up the barrel is the art. I guess I thought that threads were threads and that as long as they were square allowed full seating, you were there. That was the reason I chose Shilen, they were willing to chamber and thread both ends. I suspect other barrel makers would also do that if given a few rounds to properly headspace, but as you say it would not likely be done with extreme care.

    I read about using a longer thread area, e.g. instead of approx 1" of thread machining up to 1.5" of thread contact to insure proper alignment, would that make up for less than custom threading?

    Thank you both for your kind response, I suspect this hits a bit close to home, truly there is no intent to offend on my part.
    Best,
    Ross
     
  5. CatShooter

    CatShooter Well-Known Member

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    [ QUOTE ]
    The action comes ready to go, the barrel can be ordered chambered and threaded on both ends, trigger is drop in as is the stock.

    So what am I missing, where does the gunsmiths artful ability come in that adds a considerable expense to an already accurate gun?

    [/ QUOTE ]

    The Shilen barrel still has to be fitted to a headspace gauge - it is NOT ready to screw in - you will need a barrel vise, an action wrench, and headspace gauges, and a lathe with a bore size that will take the barrel.

    The rest you can do if you are skilled.

    Get the pieces parts, and have a good smith put the barrel on, and do the rest yourself - fitting should cost between $100 and $150, depending on who does the work.

    Don't take it to a pipe fitter at the local gun shoppe!!

    .
     
  6. buzzgun

    buzzgun Well-Known Member

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    Fifty (and anybody else that knows the answers)

    I'm trying to learn something here......

    Can you explain why the precise threading you described above makes a big difference in accuracy????

    I guess I'm thinking like Ross......if the barrel/receiver faces are square and screwed together tightly, I don't understand why such precision threads would make any difference???

    Does the barrel shank have to be threaded for the combination to be accurate??? What if the inside of the front of the receiver wasn't threaded at all, and the barrel shank had no threads either......could you machine each so that barrel to receiver assembly was a press fit, held in place by pins, and still be accurate??? Wouldn't that remove ALL clearance issues if you have no clearance???

    What if we machined the barrel shank and the receiver so that the receiver had to be heated slightly to expand and allow the barrel to be press fitted??? I'm thinking about how connecting rods in an engine are sometimes heated in a fixture until they expand enough that the piston pin can be installed.....why couldn't a barrel be installed the same way and remove ALL clearance issues???

    Educate me please! /ubbthreads/images/graemlins/grin.gif
     
  7. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    There are things called harmonics in barrels, if your thread fit is not "almost perfect" varing vibrations will develop, one wants the rifle to vibrate the same all the time. Even if the face of the reciever and bbl shank are square, there will or could be underlying vibrations. Not to mention if the threads are cut to about 50% contact, there can be some mis alinement in chamber to action bore, this can cause loss in accuracy, hence the reason for blue printing, remember we are talking very minor adjustments. We are also talking about serious stresses being imposed on the threads and the locking lug abutments from the chamber pressures, 60,000# will have a big effect on the threads, the better the contact in threaded area will reduce bad vibrations. The only way to achieve good thread contact is have a action that is threaded perfectly and match the bbl to the threads. No prethreaded bbl will perfectly match a action, unless you get lucky, its never happened to me.

    Pinned barrels, maybe on a low pressure case???? High pressure rounds, most everything will shoot is a high pressure case, 45,000# and on up. Eventully the bbl will start to move or shear off the pins, leaving a very dangerous situation.

    Heated and pressed on, how would you know if its pressed on straight? With an interferance fit, there is still metal to metal contact. We measure bbl to action alignment in the "tens of thousands" or tenths...if would work, it would of allready been done. A quality set of threads is the way to go, you need a good gunsmith to achieve this, he has to have patience along the way. You cant rush putting on a bbl.

    Just my .02

    Dave
     
  8. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Think of it this way. If the thread fit is loose, when you tighten down the bore, only one surface will be contacting between the receiver and barrel threads. If you have a precise thread fit, the entire system is much more like one unit then two seperate only contacting on a small single surface of the threads.

    As far as press fit barrel shanks, there are many out there already, on low cost 22 rimfires mostly. If it were a better system we would be using it.

    If a standard thread fit was better then a precision thread fit, all BR rifles would be so threaded.

    I can not explain the harmonics or physics of why it works, at least not to the point anyone would understand what I am saying. I am a pretty simple guy, you do what works, you test things and prove what works. A Precision thread fit will be more consistant then a loose thread fit everytime if everything else is equal.

    Also, if your using long heavy barrels, there is alot of stress in the receiver thread, receiver face, barrel shoulder area. Again, a precision thread fit supports heavy long barrels MUCH more consistantly then a loose thread fit.

    If you want a 1 moa rifle, go for it. Possibly even a 3/4 moa rifle. I will not say you may not even see an occasional 1/2 moa group. But to improve much below that, you need perfection at nearly every point in the rifle building process. Again, its nothing secret or special to do, you just have to do it and do it correctly to get the results.

    Test your press fit theory and run it up agaist a precision built rifle and see how it holds up. One main thing would be strength of such a system with high pressure, high intensity modern rounds.

    Not sure I can educate you but I can tell you that this is the best way to get consistancy.

    Kirby Allen(50)
     
  9. buzzgun

    buzzgun Well-Known Member

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    Dave
    Thanks for the input.

    I understand about harmonics, not sure I agree that 100% thread contact verses 90% thread contact would make any measurable difference if the face of the receiver, the recoil lug and the shoulder of the barrel are both square???

    As far as the heated and pressed fit goes.......are you saying you can get a straghter fit with a threaded connection (which must have some clearance) than you can with an interferrence fit that has NO clearance??? Think about it this way.......you counterbore the receiver 1.5" deep with a shoulder at the bottom that acts as a positive stop for the barrel shank......you then machine the barrel shank so that the receiver has to be heated in order to for the barrel to be pressed into the receiver......after the receiver cools, there is NO clearance.......how could the joining of the barrel and receiver be any straighter???

    By the way.....this has been done on some expensive rifles for many years......they aren't chambered for low pressure rounds......and they don't shear pins......


    Just because we have always done something a certain way does not mean it's the best way.....especially with the improvement in technology we see almost daily.......look at the custom 700 replacement actions on the market right now......nothing like that was available at anywhere near the current cost until recently!

    Just trying to ask a few question and hopefully learn something!
     
  10. buzzgun

    buzzgun Well-Known Member

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    Kirby

    In a threaded system, there must be clearance or the action won't thread onto the barrel....right???

    In a interferrence fit system, there is no clearance between the receiver and the barrel......right???

    So, if we eliminate the strength/pressure concern (and we have the technology to do so)......why wouldn't the press fit be a superior system???

    Unfortunately, I don't have the equipment to test such a system.......but my engineering background tells me it would work......

    Maybe the reason we don't see widespread use of interferrence fit barrels is not because a threaded system is a better system, but, maybe it's because the threaded system is easier to work with??? The biggest problem I see with an interferrence system is the difficulty of getting the headspace correct without having to test fit the barrel and receiver......it wouldn't be easy to pull the barrel to make adjustments! /ubbthreads/images/graemlins/grin.gif
     
  11. Cruizin

    Cruizin Well-Known Member

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    Buzzgun,

    A press fit introduces stresses in the metal and those stresses will increase and decrease as the metal heats up and cools down, therefore, probably causing more inconsistencies. Inconsistencies and accuracy don't work well together.

    I'm not a machinist but I have designed enough parts to feel that a quality thread would be better. If the barrel's center axis is not right in line with the action then your not going to shoot straight. One reason that comes to mind would be that you could ream the chamber and make the threads without having to take the barrel out of the lathe. Reducing the amount of operations usually allows for tighter tolerances.
     
  12. buzzgun

    buzzgun Well-Known Member

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    [ QUOTE ]
    Buzzgun,

    A press fit introduces stresses in the metal and those stresses will increase and decrease as the metal heats up and cools down, therefore, probably causing more inconsistencies. Inconsistencies and accuracy don't work well together.

    I'm not a machinist but I have designed enough parts to feel that a quality thread would be better. If the barrel's center axis is not right in line with the action then your not going to shoot straight. One reason that comes to mind would be that you could ream the chamber and make the threads without having to take the barrel out of the lathe. Reducing the amount of operations usually allows for tighter tolerances.

    [/ QUOTE ]

    Thanks Cruzin

    Are you saying that a threaded joint expands and contracts less than a press fit joint???? Are you saying a threaded joint doesn't induce stress that increases and decreases as the metal heats and cools???

    Doesn't the coefficient of expansion of a material remain the same regardless of the shape of the object???

    Maybe you are saying that the clearance on the threads gives the barrel expansion somewhere to go??? If so, I don't understand how that could happen since a threaded joint has zero clearance on at least part of the thread.

    As far as the barrel's center axis not being right in line with the action, how will cutting threads on the barrel shank provide a better center axis alignment than a shank turned to a precise press fit??? I understand that you can ream the chamber and cut the threads at the same time....are you suggesting that you can't ream the chamber and turn the shank to finished diamter at the same time too??? Whats the difference??? If you have to turn the barrel shank to the proper diameter before threading, how is it that leaving it unthreaded would cause the barrel center axis to be out of line with the center of the receiver???

    If reducing the amount of operations allows for tighter tolerances.......then wouldn't eliminating the threading operation allow for a tighter tolerance???

    How can a threaded joint, which MUST have clearance to work, be more precise than an interferrence fit that has zero clearance????

    Just thinking outside the box.......
     
  13. Cruizin

    Cruizin Well-Known Member

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    Those are all very good points and I have to admit I didn't think it through before my first reply. Right after I posted the first time I noticed you had posted again and talked about head spacing. I think you nailed it with the fact that barrels are just easier to remove when threaded.
     
  14. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Buzzgun,

    YOu may have hit the button right on the head, just not practical to work with.

    Plus I am not sure that over long term use the press fit system would hold headspace adjustment like a threaded receiver would.

    I believe the fabulous Rem 710 rifle has a press fitted receiver. Have you heard all the rave review of this receiver, me neither!! /ubbthreads/images/graemlins/grin.gif

    Yes there has to be some clearance for a thread system to fit properly without gauling but you can get it extremely close, so close in fact that it limits any directional shifting to really speak of. Using specially designed internal and external matching thread cutters you can get a thread fit that has no preceptible slack of any kind.

    I like my barrels to be tight enough that I have to use a quality anti gaul compound and have to wear a glove to thread the receiver onto the barrel. In most cases I can not thread it on bare handed because the thread fit is so close.

    You have to be careful doing this with some receivers. I have found that with Nesika Bay receivers, they do not like being this tight and have a very high potential for thread gauling even with a quality lube so they can not be fitted quite so tight but there should still be no preceptable loosness between the receiver and barrel when the receiver is threaded onto the barrel but not contacting the barrel shoulder. This is when you know the thread fit it correct.

    In my opinion, with all the development and testing that has been done in the firearm industry, if a press fitted barrel was a better system for accuracy and consistancy it would have been done and would be being used today.

    The boys in the BR world care very little about cost of their rifles, at least the real serious ones. Only thing that matters is getting that group smaller.

    Practicality may be a huge issue and I am sure it is. I just do not see how a press fitted barrel would have any advantage over a precision threaded barrel.

    Headspace adjustment for one would be a real pain in the rear.

    Only way to prove a theory is with actual real world testing which is often spendy. Even if the result was better, would it be that much better to warrent the added trouble in working with such as system? Personally I do not think so but that is just my opinion.

    A better system may be to use a barrel and locking bolt that actually locks into the actual barrel. This way there receiver to barrel interface would really not be a stressed system, just between the bolt head and barrel which would be one system. There are some receivers out there using this type of system already. You see it most common in some rotating bolt shotguns. IT works but it is very labor intensive to build. With todays CNC machines, it would be easy to do but still, is it better then what we are using now????

    Kirby Allen(50)