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Thread: Action deflection

  1. #1
    Boolit Master Hannibal's Avatar
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    Action deflection

    I saw a discussion elsewhere concerning action truing, Rem 700 actions to be specific. The discussion revolved around the different methods for action truing. IE - piloted reamers and taps as opposed to lathes, lathe fixturing and single point cutting. The discussion went on at length about which methods were more accurate and how to measure improvements.

    So. The gist of the discussion wound up being, what the gunsmith is attempting is to have the receiver ring, lugs and bolt hole as perpendicular and concentric as possible. Likewise, the bolt face, lugs and bolt body perpendicular and concentric as possible to itself and the receiver. No problem, that's all well and good and I 'get' that.

    Where I became confused was when the discussion turned to 'bowed' receivers. I can certainly see how a receiver could be manufactured with a 'banana' shape to it in a high volume manufacturing facility. Likewise, it seems custom actions are not immune from this condition, either. And the proposed solution was to make the corrections that were possible to true the action to the center line as much as possible, as the bolt body will find center.

    OK. Had to think about that for a bit, but I follow.

    SO. I posed the question, what happens to the finely trued receiver when you hang an 8 lb or more heavy/varmit floated barrel off one end of the action? The answer was, proper bedding will prevent action deflection. So. I asked, just how far from the recoil lug toward the muzzle end does the bedding need to extend to compensate for the barrel weight and prevent deflection?

    As yet, I have received no answer.

    I freely admit I do not know the answer to this question. I suspect complete elimination of deflection is simply not possible, but I'm just guessing.

    So. If anyone here knows the answer to my question, I would appreciate any method and explanation you would be generous enough to share.

    Thanks for lookin' at my post.
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  2. #2
    Boolit Master pietro's Avatar
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    .

    IMHO, if the weight of a heavy barrel bends actions, there would be millions of bent rifles out there - and there's not.

    .
    Experience is a wonderful thing - It lets you recognize a mistake, when you make it again.

  3. #3
    Boolit Master Hannibal's Avatar
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    Quote Originally Posted by pietro View Post
    .

    IMHO, if the weight of a heavy barrel bends actions, there would be millions of bent rifles out there - and there's not.

    .
    I understand your position/point of view. The posters on the other forum were arguing about receivers trued within .003" or less.

    My question is about deflection, not 'bending' as such.

    My position was/is hanging a 7 lb+ bull/varmit barrel off an action is going to cause more than .003" of deflection, so at what point does all the 'anal retentive' action truing REALLY matter?

    Like I said, I freely admit I do not know. I'm hoping someone who knows will come along and show me the error of my thinking.
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  4. #4
    Boolit Master
    lefty o's Avatar
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    there is a reason the old BR shooters sleeved the remingturd action. the 700 action is not all that strong, its greatest feature is the round front rcvr ring, everything behind that was a compromise.

  5. #5
    Boolit Master
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    Actions are said to bend/deflect under firing loads because they are not symmetrical,ie cutout for loading port.I have alway.s wondered why not free float the action,and bed and recoil lug a length of barrel.With alloy insert plastic stocks this should be easy.

  6. #6
    Boolit Master Hannibal's Avatar
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    Quote Originally Posted by john.k View Post
    Actions are said to bend/deflect under firing loads because they are not symmetrical,ie cutout for loading port.I have alway.s wondered why not free float the action,and bed and recoil lug a length of barrel.With alloy insert plastic stocks this should be easy.
    Interesting concept. I've seen rail guns built on a similar fashion, and while the weight is a limiting factor, they certainly shoot extremely precise.

    You don't see many of these. Extreme precision and extreme weight does not seem to appeal to many. Something to ponder. Thanks for your post.
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  7. #7
    Boolit Grand Master

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    One thing that helps with allievating defection is the biggest share of trued actions are bedded or pillar bedded. some are locked into a metal trough matching the action and the action screws lock them in front and back with torqued action screws greatly stiffening the action from flex. Once locked into the stock the action is held and supported.

    It used to be some 22s had the barrel bedded and the action left to float. Iron Monsters and some bench rest unlimited guns had a block fitted into the stock and a turned section on the barrel ( usually around 4" in length ) was fitted to this clamp block ( like a bearing with half cap) and clamped into the stock. This let the action float some claimed this was harder on triggers and also would hinder feeding from a magazine. But the action floated and the front of the barrel floated. Draw backs were the blocks were a custom made affair and time consuming. They weren't normally interchangeable. And when weight became a consideration in various classes or competition they added quite a bit of weight that had to come off else where.

    The Iron monsters ( return to battery rifles) at 80-150 lbs set up in this manner and tuned in can be quite impressive with the groups they produce in good skilled hands.

  8. #8
    Boolit Master Hannibal's Avatar
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    Quote Originally Posted by country gent View Post
    One thing that helps with allievating defection is the biggest share of trued actions are bedded or pillar bedded. some are locked into a metal trough matching the action and the action screws lock them in front and back with torqued action screws greatly stiffening the action from flex. Once locked into the stock the action is held and supported.
    I understand bedding and pillar bedding, at least I THINK I do . . . but I still have a hard time understanding how any action, Rem 700, Savage, Winchester 70, or any custom is not going to deflect with a 7, 8, 12 lb barrel hanging off one end of it.

    Does it matter? Apparently if it does, it is manageable. My question mostly revolves around the heated discussion about truing the receiver and bolt to within the closest tolerance possible, then hangin' that big ol' barrel off the end of the receiver and all your hard earned tolerance work is dashed right there.

    Or can I not see the tree through the forest?
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  9. #9
    Boolit Grand Master

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    A lot of high power rifles these had pretty heavy long barrels on them My pre 64 model 70 coarse gun wers a hart otc countour 26" long 1.25 at breech and .900 at muzzle. rifle with the tubs stock bedded rail and adjustable buttplate and cheek piece weights 14 lbs ( and to think I lugged that monster around the range all day). The action is pillar bedded on 5/8" aluminum pillars this supports and when bolted in at 60 inch pounds torque helps to stiffen the action. from recoil lug front of action forward 3" of the barrel is also bedded for added support. this covers a little more than the chamber length. SOme used to claim that bedding the barrel would cause more deflection or flex from the heat expansion. Eve in the "rapids" this rifle fired 2 sighters a pause while targets were cleaned up and the line called, then 10 rounds 5 and 5 the longest string normally fired were of hand 20 rounds and 2 sighters usually over 12-15 mins for me. And 600yds slowfire again 22 rounds with a 20 min time limit. When not shooting rifle was cooling while I scored or was in the pits.

    Basically the truing makes the action more concentric the fitted stock and bedding make it stiffer and support it. In actuality reaming or boring a Remington action to true it up is weakening it slightly due to the metal removal. Heres another thing one part of the accuracy smiths truing is to fit sleeves to the bolt body or a new bolt fitted close to the trued action. If the heavy barrel was flexing the action much these bolts would be binding or tight.

    I have see the sleeved 700 short actions used for long range guns and even considered building one. they do stiffen the action a lot, from the lack of the mag cut, the intregal weaver/pickatiny bridge on top and the added size. another added stiffing is the press fit that locks it together. ( this is usually done freezing the action and warming the sleeve shrinking the 2 together) but it does stiffen the action some.

  10. #10
    Boolit Master Hannibal's Avatar
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    Quote Originally Posted by country gent View Post
    -SNIP- Basically the truing makes the action more concentric the fitted stock and bedding make it stiffer and support it. In actuality reaming or boring a Remington action to true it up is weakening it slightly due to the metal removal. Heres another thing one part of the accuracy smiths truing is to fit sleeves to the bolt body or a new bolt fitted close to the trued action. If the heavy barrel was flexing the action much these bolts would be binding or tight.
    AH! Now the wheat is separating from the chaff.

    This is one of my fundamental questions. IF the receiver/bolt were ACTUALLY being trued to .003" or less, how the heck is that same action going to be able to be manipulated in and out of battery unless the deflection is at, or very near -0-. when the barrel is installed. (?)

    Second fundamental question. If piloted thread taps and piloted lug reamers are so poor a choice as compared with lathes and single-point tooling because minimal pressure causes substantial deflection in the piloted tooling, why is this not the case when the bull/varmit barrel is installed on the action? Are receiver actions the only component of a rifle that are immune to deflection?

    And lastly, if there is no significant or problematic deflection of the action, then why, oh why, would anyone go thru the trouble of sleeving an action? A short action in particular?

    I just don't see the consistency here.

    Either perfect receiver/bolt truing matters, or it doesn't.

    Either prefect bolt/receiver truing is attainable, or it isn't and corrections must be applied.

    Tell me where I'm wrong, please.

    I'm not interested in arguing. Just learning.
    Last edited by Hannibal; 03-09-2018 at 11:36 PM.
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  11. #11
    Boolit Master
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    you may want to get yourself a copy of "rifle accuracy facts" by harold vaughn. its getting to be an old book, but covers much of what your questioning.

  12. #12
    Boolit Master Hannibal's Avatar
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    Quote Originally Posted by lefty o View Post
    you may want to get yourself a copy of "rifle accuracy facts" by harold vaughn. its getting to be an old book, but covers much of what your questioning.
    I've been looking. Not easy to come by, or cheap.

    Thanks for the reminder.
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  13. #13
    Boolit Grand Master

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    When building a true accuracy rifle, NR high power, benchrest, long range fclass or others the main reason for the truing blueprinting is to keep everything as straight and true as possible. The action is touched up cleaned up from the threads to the bolt race way the lugs. the bolt is also sleeved up to the new fir and face recut to center. Luggs are squared and receiver face squared, The barrel is indicated in at both ends the tenon is cut and threaded then the chamber cut. Countour may be touched up if there is run out between hole and outside also. All this is don't to maintain the straight true concentric center line off the chambered cartridge with all the bolted together components. Threads in the receiver are cut larger and the tenon threads there are cut to a proper fit for the new threads in the receiver. Once all this is done and the rifle properly bedded into a stock then any flex in the action from the heavy barrel becomes a constant. A unstressed action bedded into the stock will match to the bedding when locked in place. One of the tricks bench resters use is to bed and tune the rifle then glue it into the stock, making the 2 as close to onepiece as possible.
    Ive seen many rifles barreled with "drop in barrels simply screwed in and chambered. These shoot a little better than factory. The ones trued blueprinted and all the accurizing done will get under 1/2" and some bechrest get in the 1s and 2s at 100.

  14. #14
    Boolit Master uscra112's Avatar
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    How is this relevant? If you are shooting off a bench the weight of the barrel is on the front bag, is it not?
    flectere si nequeo superos, acheronta movebo

  15. #15
    Boolit Master Hannibal's Avatar
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    If your barrel is being supported by the front bag . . . .

    Where did you place your front bag?


    And I think I'll just stop right there.

    My head hurts.
    Missing the target is not the worst thing you can do.
    Not taking the shot is.

  16. #16
    Just try making a shim washer, tapered from one side to another, to go under your shellholder and size a case with a slightly canted base. It won't be at all easy for firing with anything but very high pressure loads to restore that base to square - or the 89.8 degrees of a production Remington action. The awful thing shown in this picture, someone's attempt to develop, if you can believe this, an Improved .244H&H on the full-length .375 H&H case), would do so. But my .40-82 Winchester, firing medium pressure but far from limp-wristed smokeless loads, doesn't even shift the case back to reseat primers extruded to the full extent of its .005in. headspace.


    Click image for larger version. 

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    It wasn't me, honest!

    There must be some reason why we bother with bolts at all, when they are such a nuisance. I suppose a wet or oily chamber, or a case separation, is a game-changer. But I think blueprinting a Remington action is only likely to be of practical advantage to someone trying for benchrest records. But how many people who are that keen are really using Remingtons nowadays?
    Last edited by Ballistics in Scotland; 03-10-2018 at 09:28 AM.

  17. #17
    Boolit Master
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    I understand that the action may not be perfectly true in relation to the bore but what matters is the relationship of the bolt head, lugs and locking recesses when the bolt is closed.

    Deflection of the raceways might have some effect on the bolt travel when the bolt is open but on a receiver with forward locking lugs, most of that receiver is out of play when the action is closed. Or in simpler terms, when the action is closed the only thing we need to worry about is the receiver from the locking recesses forward.

    Now in a rifle with a bedded receiver and a free floating barrel, all of the stress from that free floated barrel is transmitted to the receiver but again, as long as the forward portion of that receiver/bolt remain concentric with the bore, who cares if the rear of that receiver deflects a bit?

    When we get into the giant heavy barrel bench rest guns, things change a little in terms of where we attach the stock to the action and the strength of the receiver. However, when we start talking about custom made giant bench rest rifles, we are no longer comparing apples to apples when talking about average rifles and bench rest rigs.

  18. #18
    Boolit Master
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    Quote Originally Posted by uscra112 View Post
    How is this relevant? If you are shooting off a bench the weight of the barrel is on the front bag, is it not?
    the weight is still on the action. there are some people ive seen actually rest the barrel on a bag, but that causes untold problems with accuracy.

  19. #19
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    If you want a seriously good action, just buy a Defiance to start.
    http://defiancemachine.com/
    The solid soft lead bullet is undoubtably the best and most satisfactory expanding bullet that has ever been designed. It invariably mushrooms perfectly, and never breaks up. With the metal base that is essential for velocities of 2000 f.s. and upwards to protect the naked base, these metal-based soft lead bullets are splendid.
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  20. #20
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    I have no business participating in this conversation but I was under the impression that the "floating" bolt head as savage is what aids those type of actions have very good accuracy for what they are. That would maybe cover for flexing?
    Look twice, shoot once.

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