Bowed Barrel

[Joseph Scott 0]

I just put sporter barrel in lathe to install lug and sight. Found barrel is bowed in middle at .052". Worse I have seen. I don't have experience in straightening barrels. Looking for someone who I can refer owner to. It may shoot straight but I don't know. This barrel should have never been sold like this. Does anyone have a barrel press and knowhow?

[Ed Johnson 0]

Joe, as we already know from Johnson Automatic's films, they used a barrel straighting press during production. I always did wonder about accuracy if a barrel had to endure such a proceedure.

We can assume that either heat or physical damage caused the warp, in your case.

Back in the '60's, a friend heated up a .45 ACP Thompson barrel in a standard gas kitchen stove and was able to straighten it to proper form. However, this would hardly be the most professional method.

I suggest you contact someone like our 5.7 Club Gunsmith, Richard Hoffman, who also manufactures a .22 rimfire replica of a Gatling Gun. He is at:

Bwefirearms@aol.com

Another source, rather obviously, would be a machine shop and/or barrel manufacturer. What about someone like Springfield Arsenal?

Good luck and keep us posted. Ed J

[Joseph Scott 0]

Ed, thanks for the leads. A Johnson factory staightening press is located in Mass. north of Providence. It and a deep hole barrel drill were purchased at the auction and are still being used. I think name is Gartman or Goutman Arms. Walt knows them. Most barrels were/are cold staightened so they could be handled while sighting through the bore. I suspect this was a surplus barrel which was machined to Johnson contour thereby releasing stresses which warped it. Most war production barrels were not doubled annealed which left stresses. They were cold straightened in their original contour.

[ArtR 0]

I am neither a ballistician nor gunsmith, so bear with me here.

I cannot believe all arms manufacturers test all barrels for true straight prior to assembly. Neither can I believe that all manufacturing stresses are relieved prior to assembly. While any barrel deviations out of true straight would create stresses on the projectile and the barrel, the real question is, how many other barrels are out there today with minor issues with out of true straight? My guess is there are more than we would want to count.

Also consider where the out of true straight may have come from? Did it occur originally in the factory or did it happen one day when a hot barrel went through some abnormal cooling? Or was it the result of normal built in stresses realigning themselves? That is, maybe this was a barrel that was cold stressed to a straight position at the factory just realigning itself?

The next question to pose would be, if there are barrels that are out of true, what is an acceptable deviation? Is it as little as .001" or is a much higher number acceptable? We seldom worry about throat erosion until it gets well above a 2 or 3. While none of us want this, after the first shot, it begins.

Johnson Automatics employed the use of a cold straightening press. At what deviation did they need to begin to straighten? To what level did they straighten it? What was considered straight enough?

Another question that needs to be answered is has it affected the accuracy of the barrel? Is it the dynamics on the projectile going down the barrel or those acting on it just as it leaves the barrel that are going to really affect accuracy. Once the projectile has achieved velocity and rifling has begun its rotation, after it leaves the barrel, other than an unanticipated obstruction, normally only gravity, drag, and wind forces act on the projectile until it reaches the target.

Unless the barrel was truly out of round or was bent so grotesquely that it would be an obstruction, at what point does this become an issue?

[Joseph Scott 0]

The description of checking a barrel for straightness describes looking through bore at a horizontal line such as on a window and rotating the barrel. The line should look same (straight) in all positions. I have no idea how this translates into mechanical measurements. A certain amount of off center-line bore is allowed in commercial guns, but not usually in military. The books on making 1903 Springfield rifles (also K98 Mausers) call for checking all and straightening as needed. No specifications given, just that lines are right. For the Shilen barrels that I use, they told me it is a specially inspected "ordnance grade" steel and is bought stress-relieved. After boring, they stress relieve again, before rifling, to insure straightness. I suspect only premium barrels are so done, not commercial production. This barrel also has below minimum headspace for .30-06, so I suspect unskilled person built it from a surplus barrel.

[Joseph Scott 0]

I test fired the bowed barrel with customer's bolt and it shoots 8" to right and 3" low at 25yds. With windage adjustment all the way over, it is still 3" to right at 25yds. The barrel had numerous half-moon pits on it and owner says receiver has same. I now think it was in a fire and warped while stored in a corner. The moon shaped pits may be water drops corrosion as the moons are all in same direction. Anyway, we found several gunsmiths who straighten barrels and also a barrel press made by B-square. Will post results when done.

[Alasdair MacDonald 0]

Bowed barrels are a normal condition that barrel makers have to live with. When I visited the Springfield Armoury they had several of the look through devices as described by Joseph Scott. They are mounted from the ceiling and are at a 45degree angle so the operator can look through them. The circular wheel has mutiple handles around the edge that resembles a ships steering wheel(helm). They look through it and apply foot pressure to a device that puts pressure where the bow takes place. When this same condition occurs in males, it is called, "Peyronie's Syndrome" and also causes one to shoot in the direction of the bend a la our former President. Cordially, Alasdair

[Joseph Scott 0]

Straightened the bowed barrel from .052" to .003" and it now shoots 1" low and 1/2" right at 25 yards, about normal. Staightened it by puttin it in v-blocks on a milling maachine table with a heavy bar across top to pull down while watching a dial indicator. It took .325" down bend, (and lots of pucker power), to straighten. I now think this gun was in a fire as the op handle plunger spring was dead soft. Rifle is in NJ. Can anyone nearby offer to inspect receiver, etc for overheating/warping?