Timing a Barrel, how much impact in Long Range?

Discussion in 'Gunsmithing' started by AJ Peacock, Dec 27, 2007.

  1. AJ Peacock

    AJ Peacock Well-Known Member

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    Happy Holidays everyone,

    I've been doing a lot of reading about gunsmithing and have a question. I understand that for extreme accuracy, a barrel is timed so the natural arc of the bore is pointing directly up at the muzzle.

    My question is, how much difference does it make?

    For example, with a Savage and barrel nut configuration, the headspace is set with barrel turn so timing the barrel is impossible.

    It make sense in my mind to have a barrel timed for ultimate precision. Maybe this is one of the reasons that gunsmiths like to setup Savage's in the same way that other actions are setup (with a shoulder and no barrel nut)?

    Just curious if anyone has any objective observations, or is timing the barrel one of those things that is 'just done'?



    AJ
     
  2. James Jones

    James Jones Well-Known Member

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    Well think about it ,if the natural curve of the barrel is to the left then the bullet is getting started that way and that will only increase with range and theoreticaly speeking if the barrel is indexed pointing to the left then the windage is gonna be differant to one side than the other :eek: and thats gonna suck trying to find a dope sheep out on that one.

    I think that you would be supprised at the amount of guys that build accurate rifles for a living that are not concerned at all with this , especialt target shooters as their target is gonna be at prepositioned ranges each time and only the windage has to be adjusted most of the time. On all of the guns I have built I indexed the barrel with the curve pointing up just because I feel that little extra is worth worrying about. I have only heard one other gun builder that has mentioned this and thats Nathen Dagley ,this is a big reason that I endorse him whole heartedly as these small attentions to detail all apy off.

    With the Savage its not that hard to install a barrel with it being indexed cuve up , as long as the chamber is not finished cut. The two i did with the barrel nut I installed the barrel so that with the nut snug and the curve up the bolt would just close , the barrel and action were then both whitness marked for the reinstall , the barrel was pulled and then reamed just like you would with a conventionaly shouldered barrel , one of these was done iwht a pull through reamer that worked realy well , it takes two people , one to turn the reamer and one to apply pressure to the reamer with the bolt. Once the bolt closes the reamer is turned with no pressure on the closed bolt till it turns freely , generaly about on revolution. is each case the chambers were cut to the tight side of min spec so that they would just get snug the last 10% of the bolt closing.
     

  3. AJ Peacock

    AJ Peacock Well-Known Member

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    James,

    Thanks, what I meant was 'just installing a pre-fit Savage barrel' you wouldn't be able to index. Obviously if you are cutting the chamber, you can index it.

    I just watched a DVD by Grizzly that had Gordy Gritters chambering a barrel; and indexing it is one of the things that he did.

    Can you tell me a little more about 'pull through reamers'? I suppose with one of those, you could order a short chambered barrel and finish it without need of a lathe?

    Thanks,
    AJ
     
    Last edited: Dec 27, 2007
  4. royinidaho

    royinidaho Writers Guild

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    Excuse me fella!!

    What in the world are you guys talkin' about?

    "natural arc of the bore" what the heck is that?

    Never heard of such a thing:confused:
     
  5. AJ Peacock

    AJ Peacock Well-Known Member

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    When a hole is drilled in a barrel, it isn't perfectly straight (even though the barrel maker strives for it to be perfect). It will not be centered perfectly in the barrel and it will wander a little (hopefully just a single very slight arc) from one end to another. The really picky smith's will want that slight arc to be indexed to point straight up at the muzzle.

    AJ
     
  6. James Jones

    James Jones Well-Known Member

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    Thats right , theirs no way to drill a hole that deep and have it strait , so some barrel makers will straiten the barrel and this is major reason that some barrel "wander around" so much when they heat up because of the stree that was introduced into them during the straitening process. supposedly Dan Lilja is the man to drill deep strait holes and supposedly Lilja barrel have less curve than any others.

    I have tried several barrel makers and have found that Kreiger and Hart barrel are pretty damn strait , never tried a Lilja or Rock Creek or any of the newer barrels. I spun the barrel in a static rest thats desgined to check the straigthness of pump shafts (like the units desgined to check your loaded ammo's runout) with the barrel supported at one end and the middle , I put a range rod in the breech end and the muzzel and set up dials on both and gave it a turn , you would be amazed how much a little last word dial moves on the muzzel end.

    Like I mentioned before you would be supprised how may guys don't worry about it when they build their guns and I'm talking about guys that build world class long range target rigs , its probably realy nothing to be concerned with but I feel that every little thing I can do to stack the ods in my favor is worth the extra effort.

    Guys that bitch and whine about the prices that smiths charge to blueprint an action and install the barrel just don't understand , if they new the hassel that goes into doing a quality job they would relize what a bargen they are getting !!!
     
  7. royinidaho

    royinidaho Writers Guild

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    Thanks for the enlightenment fellas!

    I'd never tho't or heard of that.

    Regarding the smith's worth: It amazes me that they work for so little. Pretty much like the pilot that flies me around taking aerial photos. I multiplied his asking fee by 3 so I'd feel good about it. The only thing between my butt and the ground is air in that pecker wood 1974 Balanca Scout and he's the guy that keeps it in shape.

    I just wish I could get the rifles returning a little revenue once in awhile;)
     
  8. lazylabs

    lazylabs Well-Known Member

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    James

    How do you support the barrel in the middle so you are certain that it's concentric with the bore at that point?
     
  9. James Jones

    James Jones Well-Known Member

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    The barrel is restng on the outside , the static resthas two pairs of wheels that just cross eachother and is adjustable for the sapce you need.

    Now I know what your thinking , the outside of the barrel is not concentric with the bore for all 360 deg and in alot of cases your right but for the most part the barrels are finish turned on centers so if proper care was taken to not get carried away with tool pressure and the follow rest is setp right they will be amazingly close but some are way out !! , in either case you will egneraly get a we bit of runout on the breech end maybe .0001" or so and that is taken into consideration. I saw a barrel one time that was to be setup for a Savage nut systen that wa so far off the bore that the threads coulden't be cut correctly so their are some turds out their.

    some guys swear that your barrel has to be supported at the muzzle and dialed in as accurately as the breech when the chamber is cut , but think about it , if your muzzle and breech are both running true with no runout than neans that their is a curve midstream right? Now I indicate my barrel at the muzzel but it is dialed in for the runout I found earlier , another way( much easier) to check this is to use a long needle finger on the dial indicator and rather than using a range rod you simply run the needle into the breech end once right at the mouth and one run further inside where the throat will be and get the barrel running strait this way. I was shown this buy a guy that builds gun for shooting world record quality BR match and is in the BR hall of fame. He dials his barrel in with a brass bushing slid up snug on the barrel about half way down and it rides just loose enoguh to not bind in the bore of the lathe and he dials in by adjusting a "set true" 3 jaw chuck , we argued a bit about ths process and he made a believer out of me , he guarntees his hunting guns up to magnums to shoot 3/8" or less and his bench guns shoot in the .1's or they are fixed !! its kinda hard to argue with figures like that and the fact that he holds some BR world records.
     
  10. eddybo

    eddybo Well-Known Member

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    James I been trying to make him eat one of those warranty guns...because he says he throws them in the lake if they wont make it. There are none in the lake, and probably never will be. He should just guarantee that everything will shoot in the ones and would probably still be okay. All 12 of the guns he has built for me will do it and a couple have shot in the ones at 300 yards. I think his methods are a little strange at times but who can argue with sucess. Let me know next time you head to see the old man, I will buy yall some lunch.

     
  11. J E Custom

    J E Custom Well-Known Member

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    WOW!!!!

    I though the reason for getting a custom barrel was to eliminate
    these kinds of problems.

    First I don't buy barrels that have been straitened .

    There are a lot of custom barrel makers that don't straiten' they are
    rebored to a larger size if they are not strait.

    I place all of my barrels between bore centers and check run out before
    any work is done. If it is more than .0005 mils I re contour the barrel true
    to the bore.

    Factory barrels are notorious for being straightened after being contoured
    and thats one reason some wont shoot. The worst factory barrel I ever
    saw had .057 tho run out in the middle .

    As james said I have found LILJA to be one of the best and have not had
    to recontour any of his fine barrels.

    But I have had to re contour other brands ( only once ) then bought no
    more from them.

    If you buy cheep barrels they are probably straightened to hold down cost.

    Buy only premium barrels and you shouldent have this problem.

    And as far as supporting the barrels when contouring I use a travel rest
    that attaches to the carrage and moves with the tool.

    Some barrels are tapered off the centers but the breach end is not and
    must be turned (breach end only) before cutting the tennon.

    If a barrel has been straightened and and not re contoured I won't use
    it.

    Just my opionion
    J E CUSTOM
     
  12. Rustystud

    Rustystud Well-Known Member

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    Arc and Indexing

    AJ:

    There have been two different scenarios brought up here that I am reading. One is the natural arc of a barrel due to gravity. This is a natural phenomenon and can be compensated for or just accepted. The other is the alignment of the bore in relationship where the bore points at the muzzle.

    From a gunsmiths point of view there are several schools of thought. We all will agree that barrels are not drilled perfectly.

    One school is to start off straight and end up straight. This means dialing in the barrels on both ends. Most smiths do this within .0002 or better.

    The other school is to align the axis of the case and bullet with the bore. This is done by drilling the bore out about 3/4 the lenght of the case, then boring it out with a boring bar within about .0015 of finish diameter. Then the barrel is redialed in using two points of indication in the throat area. The tendon end is dialed in crudely. Then the indicating rod is indicated near the throat and with another indicator back on the rod near the tendon face. The rod is dialed in by adjusting the spider end of the barrel.
    The muzzle end is left out of center. The high spot is marked on the chuck so the barrel can be indexed to have the high side point up with the finished barrel.

    There is a third philosphy and that is to use a floating reamer holder that floats both co-axially and concentrically. This may leave a little more runout in the web area but aligns off the reamer pilot at the throat area of the chamber. Most chambers cut this way will be within .002 or better in the web area. PT&G reamers are generally tight (small) in the web area and chambers cut with them require a little polishing to open then up.

    The with either method the end results are so much better than factory barrels and chambers that there is no comparison.

    AJ this is a real bone of contention with the BR shooting community. You will have the most heated debates on which methodology is the best.

    The idea of a tight chamber is not always the one that shoots the best. I can tell you this from experience. I chamber a fair number of precision barrels. In my opinion stress and alignment in fitting barrels to actions and bolts to actions, and actions in stocks have more to do with good or bad performance. Todays top flight barrels are all capable of shooting sub .25 moa.

    Hope I have not confused you more. I am sure some others will chime in.

    Rustystud
     
  13. AJ Peacock

    AJ Peacock Well-Known Member

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    Thanks for the info, this brings up something else I've been thinkin on.

    You mention the "Barrel to Action fit", I've seen guys lightly lap the threads on the barrels to the actions, to improve the thread to thread contact (obviously good flush contact is needed between shoulder and action).

    Along the same lines, I've been curious if there is anything that can be done to a Savage factory barrel and Action to insure good solid contact? I've heard of guys surface grinding the barrel nut to be square, replacing the factory recoil lug with a machined lug (because the factory lug is stamped and has different thickness top to bottom).

    I have a Savage that is a consistent 1/2MOA rifle (300WSM) and all I've done is change the lug and headspace it. I didn't use any thread compound, I didn't lap threads or worry about the barrel nut being square. Is there anything along those lines that might improve the fit/squareness when I install a barrel in a Savage? I'm up for some experimenting, but would like everyones opinions. I understand that with the floating bolt face, absolute squareness isn't required with the Savage, but good consistency can't hurt. Wondering about a moly grease on the threads or lightly lapping them??

    Thanks,
    AJ
     
  14. royinidaho

    royinidaho Writers Guild

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    This is a good thread! WOMH (way over my head - but good)

    Keep it rollin'