How to straighten a band spring

[Hal]

I recently bought an 1816 percussion conversion. Sometimes when I fire, the front band moves forward. At first I thought I was doing it when I grasped the muzzle end during loading, but it's definitely doing it on its own upon firing. I removed the spring to inspect and found it somewhat twisted, but worse, the pin that retains the band is not perpendicular to the rest of the spring. It leans forward, as the last 1/4" or so of the spring is bent. Can this be straightened without breaking it? I was afraid to do anything to it, so I just reinstalled it.

[Curt]

Hallo!

In brief... Cold bending will likely snap it off before it straightens. (Much depends on how it was hardened and tempered back.

It could be hearted, and heat bent. Then rehardened. And redrawn. (But if you reposition the spring pin, you will need to redo the spring's pin hole to match.)

IF the problem is it is not securing the band, you may just get by by adding a thin "shim" of wood or cardboard under the band spring in its mortise which will raise the height and compression a bit.

Curt

[Jim Brady Knap's Battery]

I've tightened weak band spring engagement by putting a piece of rubber band under the spring. Seems to work well.

[Kevin Tinny]

Thanks, Jim:
Will try the rubber band piece on mine that lets the top band move under recoil.
My spring PIN is just enough loose in the cross-pin hole that it can be moved outward slightly as the spring is compressed. That might be the real issue with mine, so will test with the rubber band piece first.

Tom Nixon shared that if TRULY NEEDED, there is another way to increase the curve in the spring:
FIRST, he lays the spring on its side and traces the existing pin and curvature as a reference.

Then he positions the bottom side of the spring on a block of flat lead so that the cross-pin will not contact ANYTHING. Then he lays a 1/2" drill shank on the outer surface and taps IT with a hammer to create a SLIGHT downward force that "expands" the curve upward. He moves the drill shank contact location about an 1/8" each whack to spread the curve a bit. He does a few whacks and compares the new curvature to the reference one and GOES SLOWLY. He said he's never broken one and has been surprised at how much of a whack the spring will take, if needed.

Breaking the TIP that goes into the hole IN the top band is a PIA situation.

I haven't built up my courage to try his way, yet. But, Tom's a wizard.

Respectfully,
Kevin Tinny

[Hal]

Thanks guys. I'll try shimming behind it, but it's not so much that the spring is weak. It's more a problem of the pin being at an angle to the hole in the band. It just rides down and out of the hole.

[Hal]

Here is a picture of the spring in question. Note bend near the pin that retains the front barrel band.

[Kevin Tinny]

Hello:
THAT's a good photo of a potential trap.

Bending that TIP section was what Tom Nixon warned me about.
Makes me wonder how it got that way without cracking.

I respectfully suggest you find an experienced person here to do it.
If he has the opportunity, Tom might be a good start.
PM me if you need contact info.

Please let us know how the problem is resolved. Thanks.

Kevin Tinny

[Curt]

Hallo!

Aha! A picture is worth a thousand words. :)

I had the Mental Picture that we were talking about the long stock pin at the other end. :)

I still maintain or recommend try a thick shim at the front end of the band spring so that the "pin' that retains the nose cap/band combo sits higher in its hol, snaps in place,
and is more secure?

Curt

[Hal]

I couldn't seem to find a rubber band around the house, but I did have some pretty thin cork. I was able to put a piece of it behind the spring. Another thing is that the front band was a tad loose and I was afraid that since the front sight is on the band, that would affect accuracy. So, I managed to get a piece of that same cork between the band and the stock and it makes for nice snug fit. Hopefully, it isn't affecting the band/barrel relationship and cause other problems. Guess I'll find out next time I shoot it. If everything seems OK when I shoot, I'll call it good. If not, I will see if I can get someone to straighten the spring.

Kevin, PM sent.

Thanks to all,

Hal

[Kevin Tinny]

Here's Tom Nixon's comment:

"They break very easy. Get calls all time about them. I think I would heat thin part then bend back into place. Don't get hot between hump and (cross) pin."

Regards,
Kevin Tinny

[John Holland]

The excellent photo shows the band spring is bent in between the forward band retaining pin and the "hump" for depressing the spring. Because of the forward angle to the retaining pin it will continue to be a problem because it just isn't securing the band. The spring is most likely a bit soft there between the pin and the hump, as you can easily see the downward bend. This is allowing the band to slide forward over top the pin, which is the effect of the recoil. You could bend the narrow section of the spring back up to bring the pin into its proper position to firmly secure the band, by the pin then having a vertical engagement in the hole in the band. I am of the opinion that because the spring is seemingly "soft" at that point it bent due to the effects of shooting it. This would be because of the recoil causing the inertia effect to place extreme forward pressure on the pin. If you do straighten it, it will most likely bend again or, worse yet, break off the next time instead of bending.

As side note, many of the ArmiSport M-1842's have broken that same pin right off the spring due to recoil and cast springs.

[John Bly]

If you get it straightened out soft solder a reinforcing rib on the underside of the spring. The rib should be at least the thickness of part right before the pin and extend back perhaps 1/4" under the hump. You can inlet deeper for the rib and it won't show. I use Brownells Hiforce 44 solder for this kind of repair. It is several times stronger than 60/40 solder and the heat to use it won't temper the spring. Even if you break it off you can repair it this way.

[Hal]

Thanks for the suggestions, guys. I will see how my cork shimming works. If it doesn't hold up, maybe I can muster the courage to try to heat and bend it. I assume we are talking getting it fairly red to orange in the thin flat area before bending?