Bending a Barrel - Part Two

[Marcruger]

I was reading the posts on bending the barrel, and thought I would make a new post so as not to hijack the other. 

Bending a barrel brings up a question that doesn't get addressed.  I wonder what the stresses are in the barrel once bent, and how that affects accuracy and grouping once the barrel heats?  How does it affect harmonics and vibration? 

With modern barrel makers (muzzleloader or back-stuffer), they often tout stress relief though heating or freezing to prevent groups walking due to internal metal stresses. 

My materials engineering classes says that when you bend a shaft (a barrel in this case), one side will have compression stress, and the opposite side will have tension stresses.  Those stresses don't just disappear. 

A very sincere question for makers:  How many of you have accuracy tested longrifle barrels after being bent?   How did they group before and after? 

I imagine the shorter and thicker barrels like a Hawken barrel would be less affected.  That said, a long thin barrel like a 44" A-Weight might be highly susceptible to stresses.   

Not being ugly, but a customer that orders a $4,000+ rifle I would imagine would be unhappy with a barrel bent to get on target.  If they are a shooter, and not a "hang it over the fireplace as art" type. 

I know old-time makers bent barrels.  That was before they had the technology to make long, straight barrels with no runout or bending. 

I am thinking that testing a rifle in the white before finishing is not a bad idea.  This is coming from someone who bought one inexpensive rifle with bad runout (9" left at 25 yards), and one that was either bent from the factory or in transit to be inlet.

Let's hear some discussion folks.

God Bless,   Marc

[Pukka Bundook]

Marc,
Cannot speak for others, but found that once a barrel was bent (Or straightened!) it stayed that way, and shot well with no group walking as it heated up, more than any other barrel.
Of course, the usual provisos apply, lugs not binding, well stocked up and all that kind of stuff.

best,
Richard.

[smylee grouch]

  If a barrel is bent and needs to be bent back, could it already be under stress and then as it gets bent back is no longer under stress? 

[Mike Brooks]

Never had any trouble shooting barrels that I bent. Otherwise, why bend them?

[Marcruger]

Brother Mike.  That isn't the question I was asking.  We bend a barrel to get them on target, with the sights aligned.  My question is what that ultimately does to the accuracy of the barrel.  As in group size.  Unless someone has worked up a decent load before and after bending, we don't know, right?  Respectfully,   Marc

[Herb]

About 10 years ago I was given a GRRW .40 caliber barrel, 7/8 by 36 IIRC.  It was a reject somebody fished out of GRRW's dumpster about 1978.  It had three or four bends in it.  We broke a couple of tree crotches with it with no straightening.  Then I took it to Bill, a gunsmith friend.  He had a hydraulic barrel bending setup.  The first bend was about twice what Daryl showed in his post here.  It took that much to keep the set.  Lesser bending straightened the other three bends.  I built a Hawken St. Louis rifle with it and tested loads in it.  It shot center and did not change point of impact as the barrel got too hot to hold.  It is second from the bottom of these rifles I built.

[Marcruger]

Thank you Herb.  Good to see you posting too.   God Bless,   Marc

[snapper]

Marc

You bring up a good question.   The question I have wondered about since you move the metal beyond the yield, what does that do ultimately for the strength of the metal in that area?  And how does it impact the different types of steels?

Fleener

[577SXS]

The only reason I see to bend a barrel is to straighten it. I haven't seen where anyone talks about the crown of the muzzle which in my opinion is the most important part of a barrel shooting correctly. The crown must be square and true to the bore. Having a straight barrel with a good crown should shoot in line with the bore. If a barrel is shooting way off when those two things are correct then I would start looking for issues with stock binding and putting pressure on the barrel. Also the traditional sights on longrifles were really low and in my mind cause issues with sighting. Drop of the comb and heel can cause issues if the stock doesn't fit the person shooting it. It doesn't take much change in sight height to change the point of impact of the bullet or ball. If a barrel has to be bent to shoot where I want it to then I want a different barrel. I would think that if a barrel is bent to shoot at a set range then it isn't going to shoot at different ranges. It may effect point of impact drastically at a closer or further range.

[bob in the woods]

A friend was " helping" me load my vehicle for a shoot, and slammed the door on my rifle which was jammed against a shooting box.  " A " weight 42 in .40 caliber barrel took a bend , which I discovered at the match when all of my shots hit the target next to mine    Thanks, bro ]   When I got home I removed the barrel and bent it back straight. Accuracy is as good as it ever was .

[Pukka Bundook]

Good post, Bob!

[Daryl]

AND, we've seen that gun shot by Bob over the last 2 years.

[Ky-Flinter]

Years ago I built a rifle with a 38" B-weight, .50 caliber barrel.  First trip to the range it shot a great group, but about a foot to the left at 25 yards, with the sights about to fall out of the dovetails.  Back at the shop, careful measurement showed it was bent left.  I did as Don Getz used to say, "Bend it straight".  It still shoots great groups, but on center now.

Ron