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Timing a Barrel, how much impact in Long Range?

 
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  #8  
Old 12-27-2007, 10:49 PM
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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?
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  #9  
Old 12-27-2007, 11:15 PM
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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.
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  #10  
Old 12-28-2007, 12:33 AM
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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.

Quote:
Originally Posted by James Jones View Post
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.
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  #11  
Old 12-28-2007, 01:30 AM
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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
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  #12  
Old 12-29-2007, 01:28 PM
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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
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  #13  
Old 12-29-2007, 04:54 PM
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Posts: 2,232
Quote:
Originally Posted by Rustystud View Post
AJ:

...
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
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
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  #14  
Old 12-29-2007, 06:00 PM
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This is a good thread! WOMH (way over my head - but good)

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