Barrel fitting

Discussion in 'Advanced Gunsmithing & Engineering' started by Cloudrepair, Feb 23, 2018.

  1. JohnMill

    JohnMill Gold $$ Contributor

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    The hardest thing for me to learn wasgiving up the "crush" when dialing in. Thanks Viper. And thanks everyone here. I continue to learn
    John
     
  2. carlsbad

    carlsbad Lions don't lose sleep over the opinions of sheep. Gold $$ Contributor

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    You'll get the best chamber if the reamer is following a bore that is coaxial with the spindle of the lathe. If the barrel is bowed and you indicate the ends, then the reamer is following a bore that immediately starts wandering from the axis of the lathe. That is the answer to the original question.
     
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  3. butchlambert

    butchlambert Site $$ Sponsor

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    Question? Have you ever seen a bowed barrel? Answer this machining question for me. Say you indicate each end, drill, indicate the throat, taper bore to the indicated throat, and ream. As you know the reamer will follow the prebored hole to the indicated throat. How much "bow" is in the bore immediately in front of the throat? .0001 or .001? Now if you just run a reamer in without the afore mentioned steps, it could be off axis and have a chamber that is large at the base.
    I do understand that we each need to chamber the way that makes us warm and fuzzy. I have never came upon a "bowed" bore, but have seen them taking off in a spiral or different directions and not "bowed".
     
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  4. carlsbad

    carlsbad Lions don't lose sleep over the opinions of sheep. Gold $$ Contributor

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    Butch,
    I've chambered dozens of barrels indicating both ends, ignoring the bow, and they all shot great.

    I've used range rods but they depend on having a perfect end to the lands so they can require some barrel prep. They are somewhat equivalent to the grizzly rod since you indicate only the end you are chambering and let the other end move away from the axis as necessary. What becomes obvious is how bowed many top barrels are. It doesn't hurt anything other than now you need to time the barrel if you want to keep it in the middle of the stock and favoring "up".

    Now I'm using the grizzly rod setup for 2 reasons:

    1. It is very quick once you learn to use it. Put it under your spider on the front side for your first adjustment and you will never have to touch that spider again other than to final tighten it and make sure it stays even. I can dial in a barrel ins 3 or 4 moves.
    2. it requires a perfectly fit bushing, which means you need to pick the bushing for your reamer and fit it on your griz rod, so now you've got your bushing picked and tested for 4 inches into the barrel.

    I find that once the barrel is dialed in this way, the other end can be out as much at .050" (.025" radially). More often it is .010 to .020. anything less than .010 is remarkable and an exceptionally straight barrel.

    So how much is that over the 3" length of the reamer? 3" / 30"= .10 x .050 = up to .005". But you'll really only have about 1/2 that since you'll even out the bow by indicating both ends so figure .0025". or .00125" radially

    Now your reamer is going to follow the bore, and if you use a floating holder, you probably won't have a problem. But if you use the tailstock without a floating holder and the nose of the reamer follows the bore off center by .00125", then theoretically you could cut the chamber about .001" to .002" oversize at the base--which is not good for brass or primer pocket life.

    That said, I think most of the time floating reamer holders are used and with proper care this shouldn't be a problem.

    I was answering the original question of what are people thinking using Grizzley rods....not maybe I'm not most people but that is what I'm thinking.

    Like I said, I've proved to myself that great chambers can be cut both ways.

    --jerry
     
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  5. butchlambert

    butchlambert Site $$ Sponsor

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    Jerry,
    Barrels do not have an arc "bow". The bores run out in different directions sometime, but not in a bow. Do you drill and prebore? What does the bushing do for you? It will follow your "bowed" hole because your bushing will be beyond your reamed or pre bored hole. I want my reamer to follow my taper prebored hole and use a very loose bushing. I do this and a lot of times with no bushing because I do not want it following a "bowed" bore. I push my reamer to allow it to follow my taper bored hole with no influence from any type of reamer holder. My reamer holder is kinda like the Bald Eagle and I push it with a machined and ground piece of steel that allows the reamer to follow the prebored hole without the influence of any external tooling.
    I did have a Gordy "Grizzly" rod in the past. If you drill and prebore it will be fine except the barrel is flopping around at the muzzle.
    As I've said before, I've used a lot of chambering methods and in the headstock and steady rest. In the many many years that I have done this, I learn a little each time and apply it to my method.
    You need to do what makes you warm and fuzzy.
     
  6. carlsbad

    carlsbad Lions don't lose sleep over the opinions of sheep. Gold $$ Contributor

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    Butch, Are we talking semantics here? I would call running out a bow. it can't run out unless it isn't straight.

    It doesn't hurt anything since it is always so small that the bullet leaves the muzzle the same every time, which is all you need.

    I agree, both ways will work.

    --Jerry
     
  7. holstil

    holstil Silver $$ Contributor

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    I think he means to say the run out is not in a single plane in that the bore wobbles a bit like a spiral.
    Is what I notice anyway.
     
  8. boltman223

    boltman223

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    I use this, all adjustments, radial and angular are done at the chuck side. I support the muzzle with an outboard "spider" if the barrel is too short I add an extension to the barrel. It doubles for use with receivers too.
     

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  9. INTJ

    INTJ Gold $$ Contributor

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    I am a new guy—have had my lathe operating for a few months now—and am still in search of my “warm and fuzzy” chambering method. So far I have chambered one barrel, a fireforming barrel that was my 600/1000 yd BR barrel in 6mm Dasher. I cut off the shank, rechambered to 6 BRA, and matched the chamber of my competition barrel.

    I have the next barrel indicated in. Four jaw on the front and spider in the back. Using Gordy’s Grizzly Rods and a snug but smooth bushing (.2368 for a .237 diameter) I have the first 2.75” of the bore running at less than .0001”.

    Since I have yet to assemble my front spider and I don’t have jaw shims I have been fussy with trying to keep the barrel stress free. I would frequently have to “unload” the chuck jaws when adjusting the spider and vice-a-versa, but think I am there. It’s easy to feel when the barrel is bending while adjusting it.

    As I think through this I do not like the idea of ME pre-drilling/boring before running in the reamer, and I especially don’t like the idea of a non-floating reamer holder.....again, for ME. I do not trust my setup skills yet.

    I want the chamber and throat area to be concentric with the bore, and it seems to my novice mind that the best chance of that happening is:

    1. By getting the first few inches of the barrel as true as possible—as Gordy shows

    2. Keeping the barrel as stress free as possible

    3. Having the reamer follow the path of the bore as much as possible, which requires a floating reamer holder and a replaceable pilot reamer with a snug but smooth fit

    It seems to me that if you pre-drill and/or pre-bore, you take the chance of making a hole that is not concentric with the bore. And if you use a non-floating reamer holder, you take the chance of the chamber not being concentric with the bore. The best way I see to avoid that is a perfect setup and a perfectly straight bore—none of which is likely, especially for a guy like me.

    Now Butch and others have been making match winning barrels for a very long time by pre-drilling and boring, so what am I missing?
     
  10. GenePoole

    GenePoole

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    Once you've got your barrel dialed in, that 2.75 inches of bore should be as concentric to the spindle bore as is reasonably possible. If you pre-drill, then the drill will follow the hole that is concentric to the spindle. If you bore, it will be concentric to the spindle, so what's the worry?

    Personally, I don't pre-drill nor pre-bore. I have a barrel flush system and it is actually faster for me to just let the reamer do all the cutting. I don't do enough volume to worry about saving wear on the reamer and I have yet to wear one out.
     
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  11. butchlambert

    butchlambert Site $$ Sponsor

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    As I have mentioned before, you will alter your methods as I have as you do this for many years. Not understanding good machining practices will slow anybody's development. Not jumping you as it appears you haven't been doing this long enough to be able to think it all through.
    One of the things that was mentioned above, both the drilled and bored hole will be concentric to the "spindle" bore. So if I indicate both ends with Deltronic pins, predrill, indicate the throat with my long reach indicator, taper bore to that indicated throat, ream with a "pusher" and what am I missing?
    You also need to remember that the bore of your bushing fit to the indicating rod is about .00015 and the fit of the bushing is smaller by .00015 of the bore. If not the bushing will neither slide on the end of your rod or fit in the bore. For example, A .2355 piece of material will not in a .2355 hole.
    I'm feeling that you and others without true machineshop training and practices might not understand this. I had rather get a direct reading from my indicator acting on what I'm trying to indicate and not on a rod and bushing that has as much as .0003 TIR out.
    All of this said, a lot of winning barrels have been chambered several different ways. I've modified my chambering methods a little over the years as I see an idea that just makes machining sense.
    Oh, how thick is a human hair?
     
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  12. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Use the reamer the whole way and use a floating reamer holder to start out. Itll do you up right. Its what id say over 99% do anyway
     
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  13. INTJ

    INTJ Gold $$ Contributor

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    Butch,

    I think I am thinking beyond where you are assuming me to be. As I mentioned earlier I am still searching for my own "warm fuzzy" and I am just not there yet. I also have significant respect for your machining and gunsmithing skills and I am NOT challenging you personally, though I have NO mercy on ideas--yours, mine, or anyone else's. I am in fact much harder on my own ideas than I am anyone else's. So please don't confuse my critical look at ideas at as anything personal. There is much value in the continuous critical examination of ideas, both in theory and in actual application. But then what else would you expect from a trumpet playing competition shooter who used to fly USAF jets............. :cool::D

    The way I see it, the goal before chambering is to ensure the entire chamber area of the barrel bore is concentric with the spindle and stress free. If BOTH of those area's are not indicated in there is no way to know if the bore is aligned with the spindle for the entire length of the chamber. It is very possible for one part of the chamber bore to be perfect with zero runout while the other end of the chamber does have runout. If a chamber is cut with non-floating tooling under that scenario it will be oversize toward the the end with runout.

    Now I have no doubt that the chambers you cut are very precise and true. I think this is how you get there. You indicate in the breech and muzzle with Deltronic pins. You do not indicate the throat yet. You have to drill first so indicator that you have shown me can reach the throat. Now your initial drilled hole will likely be larger in diameter the farther into the barrel you go because you have only indicated the breech end of the chamber and barrels are not straight, meaning here is likely some runout at the throat area. It may be an extremely small amount.

    You get everything trued up after drilling by indicating the throat area and making sure the breech end is still true. At that point, the boring bar will correct any potential out-of-trueness in the drilled hole. Then when you ream you have a true-bored hole for the reamer to follow.

    It seems to me it would be easier just to indicate in the breech and throat to make sure the entire chamber area is aligned with the spindle before doing any drilling, boring, or reaming. That is in fact why I have the Grizzly rods AND and an Interapid long reach indicator. Even though the Interapid is only .0005", when it says there is no movement, there is no movement. Also, a floating reamer holder seems to be less fussy as to barrel bore/spindle alignment, though I don't see it as an excuse to be sloppy with indicating.

    A final thought. Just as a bushing must have a clearance to fit, so must a Deltronic pin--meaning with both methods there will be error caused by the required clearance. One does not need machine shop training to understand that. You will argue that the pin has less error than the bushing because the pin only needs clearance to fit, not clearance to fit AND spin as does the bushing. I have no issue with that, and that is what I have the Interapid long reach indicator.

    Blaine
     
  14. Raythemanroe

    Raythemanroe Bullet Whisperer Silver $$ Contributor

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    I gotta believe if you indicated the chamber end in to a respectable number and the muzzle was out that would tell me that the bore/barrel isn't going to be straight unless you are flexing/bending it to read what you want..

    Ray
     
  15. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    That .0005 indicator with that long stem doesnt show much. @Alex Wheeler posted a video showing that not long ago. You can do the math on it if you like but youll be surprised either way
     
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  16. INTJ

    INTJ Gold $$ Contributor

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    I have the highest amount of respect for Alex (and many of you here—I read way more than I post), but that isn’t what I have seen. When I get the Interapid to no movement, the tenths indicator has no movement either. But who knows, maybe I just have both pushed to the end of their travel.....which BTW is the EASIEST way to get zero movement on an indicator. The next easiest way is to make sure the indicator doesn’t touch anything.............. :D

    Though I am not sure any of this matters with a floating reamer holder. One day I’ll chamber an old barrel in my three jaw (.0006” runout) and my floating reamer holder and see what I get.
     
  17. INTJ

    INTJ Gold $$ Contributor

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    Gordy and others say barrels aren’t straight and to expect runout at the muzzle when the chamber area is aligned with the spindle bore. The Bartlein HV 6mm barrel I have indicated in right now certainly illustrates that. And no, I still don’t have a warm fuzzy about it......
     
  18. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Post that video again
     
  19. INTJ

    INTJ Gold $$ Contributor

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    I concur. Based on a PM I got I see it was a mistake for me to post on this topic. Whether it's chambering, the minimum caliber for elk, what bore size for trumpet, or whether or not you should tune your truck; the Internet has ruined it all. No one knows how to respectfully disagree while debating the merits of ideas anymore.
     
    Last edited: Jun 4, 2019
  20. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Back alley hints.
     

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