Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Gunsmithing


Reply

secrets of straightening a barrel

 
LinkBack Thread Tools Display Modes
  #1  
Old 05-24-2011, 10:53 PM
Silver Member
 
Join Date: Aug 2008
Location: Houston, Tx
Posts: 182
secrets of straightening a barrel

Several years ago there was an article by a gunsmith who described how to straighten out a barrel at home. I wanted to save it but time has its way and now it is gone when I really need to apply the principles to anew barrel. It seems that most barrels have somewhat of a curve in them due to in advertant heat abberations during contouring. Your help is appreciated. 21 buck
Reply With Quote
  #2  
Old 05-24-2011, 11:23 PM
Platinum Member
 
Join Date: Jul 2004
Location: Texas
Posts: 5,466
Re: secrets of straightening a barrel

Quote:
Originally Posted by 21buck View Post
Several years ago there was an article by a gunsmith who described how to straighten out a barrel at home. I wanted to save it but time has its way and now it is gone when I really need to apply the principles to anew barrel. It seems that most barrels have somewhat of a curve in them due to in advertant heat abberations during contouring. Your help is appreciated. 21 buck

Most barrels makers will tell you that .004 to .005 Thousandths Total indicated run out is
exceptable. most smiths that have accuracy guarantees will tell you less.

I am no expert on what is the max run out so I reject anything over .0015.

I use barrels from makers that are normally close to 0 run out and have very good success
with them.

One such barrel maker explained to me that there is no real reason not to have a straight barrel
and I could send any one that is not back and he would replace it and pay shipping.

I have visited barrel shops and the main reason is that a barrel is contoured taking to much
of a cut at one time and/or stress relieving was not done correctly.

Barrels used to be straightened because the drilling process was not as good as it is now.

Some factory barrels are still straightened but it takes a high degree of skill and special
tools, Plus true north light.

If you have a barrel that is not straight SEND IT BACK.

With all of the barrels makers out there there is no reason to except anything but a good barrel
at the cost of a premium custom barrel.

J E CUSTOM
__________________
"PRESS ON"
Reply With Quote
  #3  
Old 05-26-2011, 12:35 PM
Platinum Member
 
Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,588
Re: secrets of straightening a barrel

most barrel makers are still using Pratt-Whitney gun drills from the 1950's. There are a few others out there, but most folks refuse to change, and for the most part are not anybetter. I'm not sure what they used in WWII for tooling, but I'm certain that many used the P&W's. The big difference between then and now is in the tooling, and cutting fluids (note I consider the bushing box and coolant system as tooling with these things). Drill grinds are very secretive, and often are reground off of brand new drills. How they are doing their reaming processes I can say, but it looks to me like they might be infringing on the Mapol Reamer copyrights (an extremely accurate reamer, but also very costly). The coolant is also closely guarded, and often custom mixed. The system will usually be multi filtered with at least one redundent filter system standing by. They are always at least 75 gallons and some are as big as 350 gallons. They run in a similar fashion as the basic hydraulic systems do with the same type of pumps. The grind and the bushing box are major players in keeping the bores strait and on size, and they are hydraulicly loaded with coolant and very high pressures.

Right now Eldorado is the new kid on the block (actually since the very late 1970's), but the technology is the same. They are extremely accurate, and make gun drill that drill from both ends at the sametime. Only to meet in the middle.

If tooled up right the blank should come out very strait (less than .0075"). But that becomes another problem as the steel lets go of it's stress as you drill; causing warpage as the drill goes thru. I looked at some photos awhile back of a barrel straitening machine in the Savage shop. Interesting, but I asked myself why? They now make machines that you can put the barrel in it, and it will do the job within .0005" in less than a minute! With very little stress involved I might add. Of course the big guys say you should never straiten a barrel after it's finished out. These guys always amaze me at how well they can cut a bore
gary
Reply With Quote
  #4  
Old 05-28-2011, 12:26 AM
Platinum Member
 
Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: secrets of straightening a barrel

I generally don't like cutting, bending, etc if I can't accurately and repeatably measure before and after.

Assuming I knew enough and had the tools to do the straightening piece at home, I'm not sure how I'd measure the straightness of the bore from end to end?

Gary/Jim - How do you measure the straightness of your bore?

thanks!
Richard
Reply With Quote
  #5  
Old 05-28-2011, 08:55 AM
Platinum Member
 
Join Date: Jul 2004
Location: Texas
Posts: 5,466
Re: secrets of straightening a barrel

Quote:
Originally Posted by rscott5028 View Post
I generally don't like cutting, bending, etc if I can't accurately and repeatably measure before and after.

Assuming I knew enough and had the tools to do the straightening piece at home, I'm not sure how I'd measure the straightness of the bore from end to end?

Gary/Jim - How do you measure the straightness of your bore?

thanks!
Richard
Good advice !!!!

I will try to explain the method used to straiten barrels.

Before Lasers, the excepted method was to have a Master Gunsmith place the barrel In a
special barrel press aimed at True north and looking through the bore they would apply more
and more pressure with a hand wheel about 2 feet in diameter with the barrel held between
two supports.

The hand wheel was graduated so he could apply more and more bending pressure to the
barrel and releasing it to measure rebound. the trick was not to over bend it while looking
through the bore and moving it up and down the length of the barrel.

This process was a highly skilled method and was very efective in its day.

Now barrels are checked for straightness using optical methods (Lasers ETC) and mostly
for quality control and rejected if the straightness is out of spec.

I once had a barrel that had fell over and been ran over that was slightly bent to be re
barreled. On the outside It was impossible to see the bend because it was so slight. but
when held up to the north while looking through the bore you could see that it was bent.

And about where , But With out the equipment it would be almost impossible to straighten.

Very few custom barrel makers If any straighten barrels because of better drilling processes
and the cost of straighting barrels in more than the barrel blank.

I don't know what percentage of factories are still straightening barrels any more, but with there
quality and numbers made it's no wonder that they are generally bad with an occasional
good one.

Straighting without specialized equipment would be hit and miss and it is easier to replace
a barrel that is not straight than to fool with it and risk poor accuracy.

When "Properly" placed between centers they can be measured very accurately and dealt with.

My preferred barrel maker has a tract record of nothing but straight barrels(.0000 to .0015)
and a rare one that might be .0025) end to end.

The issue on how much straightness is nessary (Some barrel makers say that .007 to .010
is OK), but as allways straight is allways better.

I have tested factory barrels that had over .050 total run out that would not shoot at all, so
they do exist.

I hope this explained the process.

J E CUSTOM
__________________
"PRESS ON"
Reply With Quote
  #6  
Old 05-28-2011, 10:22 AM
Platinum Member
 
Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,588
Re: secrets of straightening a barrel

Quote:
Originally Posted by rscott5028 View Post
I generally don't like cutting, bending, etc if I can't accurately and repeatably measure before and after.

Assuming I knew enough and had the tools to do the straightening piece at home, I'm not sure how I'd measure the straightness of the bore from end to end?

Gary/Jim - How do you measure the straightness of your bore?

thanks!
Richard
if your talking a gun barrel of any real length it's a pain in the butt. We used a few gauges that read a laser beam, and also the basic probe which reads air flow around it as it moves thru the bore (these are good for about .00015"). This is mostly for size, but will also show you a drift in the bore or out of roundness. I also built gauging complexes that would check every spec on the part including concentricity. Many of these used electronic probes that never actually touch the part. These things are good for less than .0001" variation. But the best one I ever saw in use was a simple ultra sound setup used in a military ap. I thought it was a joke at first, but soon learned it was very reliable and also very quick. All it did was measure wall thickness on a given sized O.D. We used that one on the biggest gun of them all (65")
gary
Reply With Quote
  #7  
Old 05-28-2011, 10:46 AM
Platinum Member
 
Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,588
Re: secrets of straightening a barrel

Quote:
Originally Posted by J E Custom View Post
Good advice !!!!

I will try to explain the method used to straiten barrels.

Before Lasers, the excepted method was to have a Master Gunsmith place the barrel In a
special barrel press aimed at True north and looking through the bore they would apply more
and more pressure with a hand wheel about 2 feet in diameter with the barrel held between
two supports.

The hand wheel was graduated so he could apply more and more bending pressure to the
barrel and releasing it to measure rebound. the trick was not to over bend it while looking
through the bore and moving it up and down the length of the barrel.

This process was a highly skilled method and was very efective in its day.

Now barrels are checked for straightness using optical methods (Lasers ETC) and mostly
for quality control and rejected if the straightness is out of spec.

I once had a barrel that had fell over and been ran over that was slightly bent to be re
barreled. On the outside It was impossible to see the bend because it was so slight. but
when held up to the north while looking through the bore you could see that it was bent.

And about where , But With out the equipment it would be almost impossible to straighten.

Very few custom barrel makers If any straighten barrels because of better drilling processes
and the cost of straighting barrels in more than the barrel blank.

I don't know what percentage of factories are still straightening barrels any more, but with there
quality and numbers made it's no wonder that they are generally bad with an occasional
good one.

Straighting without specialized equipment would be hit and miss and it is easier to replace
a barrel that is not straight than to fool with it and risk poor accuracy.

When "Properly" placed between centers they can be measured very accurately and dealt with.

My preferred barrel maker has a tract record of nothing but straight barrels(.0000 to .0015)
and a rare one that might be .0025) end to end.

The issue on how much straightness is nessary (Some barrel makers say that .007 to .010
is OK), but as allways straight is allways better.

I have tested factory barrels that had over .050 total run out that would not shoot at all, so
they do exist.

I hope this explained the process.

J E CUSTOM
There's a gauging company (name escapes me at the moment). They sell this machine that is pretty much a custom built one for each application. You simply lay the shaft in two vee blacks that are roughly 20% in from each end. There are two tail stock affairs that use a special centering device on each end. They sorta grab the part and rotate it two or three turns in clockwise and counter clockwise directions (the reverse rotation is key). While the shaft is being rotated a vertical probe comes in and checks for runout, and locates the highest points. It then sets the shaft back down in the vee blocks (these are not conventional as they have radiused surfaces contacting the parts). The secound head will then come in and apply pressure where it's needed to make the part strait (uses a ball screw with an encoder and a device to actually measure applied pressure). It rarely has to check the part three times, and will usually be in the five tenths range when it releases it. The machine is programed to toss out parts that are warped too much (around .025"), and parts that will not straiten after five attempts. We had them big enough to do 4340 shafts 1.5" in diameter over 40" long. But most were in the 20" to 24" range.

Most people don't realize that you can have a piece of steel perfectly strait, but when you start cutting metal it will go all over the place. EDM is not so bad, but a mill or lathe operation will change it. Nature of the beast!
gary
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: secrets of straightening a barrel
Thread Thread Starter Forum Replies Last Post
Secrets to a long Italian Marriage. royinidaho Humor 2 08-23-2011 06:52 PM
5 Secrets To Bowhunting Success ADMIN Technical Articles - Discussion 1 08-27-2010 09:23 PM
5 Secrets To A Successful Elk Hunt By Doug Rellstab ADMIN Technical Articles - Discussion 20 07-30-2010 05:57 AM
5 secrets to ELK hunting kellyzier Elk Hunting 0 06-27-2010 09:51 PM
secrets of the houston warehouse Jimm Reloading 6 02-05-2006 12:22 PM

Current Poll
Do you archery hunt for elk?
YES - 34.40%
118 Votes
NO - 48.69%
167 Votes
Not yet, but I plan to. - 16.91%
58 Votes
Total Votes: 343
You may not vote on this poll.

All times are GMT -5. The time now is 05:37 PM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC