Barrel interference with mainspring

[twobirds]

Greetings. I'm trying to pair up a Davis "Trade Gun" lock with a pretty wide barrel...1 1/4" at the breech, if I recall (shame on me for sending this from work, where I can't re-measure the barrel!). However, the lock's mainspring hits the lower side flat of the barrel when I try to place the lock in the correct position beside the barrel...which tells me that this barrel is probably too big for the lock. Of course, I can move the lock down, but this would place my touchhole in the lower half of the barrel flat.

I seem to recall that grinding the width of the mainspring is a bad thing to do. How do y'all handle this problem...lower the position of the lock, narrow the mainspring, or get a bigger lock?
Fortunately, this project is in the planning stages. I've cut no wood, and I already had the Davis lock on hand.

 

[Stophel]

Leave the lock alone. File a notch in the barrel to clear the spring. :wink:

 

[Birddog6]

Not but 4 options I can think of, if you don't want to lower the lock.

1: Change the lock.

2: Change the barrel.

3: Grind the mainspring down.

4: Grind a tad off the barrel to get the clearance.

If it is just hitting a tad, I would take it off the mainspring. Grind it longways, a little at a time, cooling it often. When I have to do one I use a belt sander & smooth it up nice & slick when done & have not had any issues with them.

And of course, it depends on the lock & the mainspring too. (I am not familiar with the one you are using)

The ones I have done this on had big mainsprings & plenty of metal.

Keith Lisle

 

[ApprenticeBuilder]

3: Grind the mainspring down.

If it is just hitting a tad, I would take it off the mainspring. Grind it longways, a little at a time, cooling it often. When I have to do one I use a belt sander & smooth it up nice & slick when done & have not had any issues with them.


Keith Lisle

I have done this, have seen no ill effects, I only take off what is needed to clear.

 

[rich pierce]

I'm with Stophel on this one, but I generally inlet my locks a little low on the side flat so this rarely happens to me.

 

[jsn]

I inlet the lock where the th is at the 2/3 mark from the top of the flat, makes for a more slender gun also.

 

[wulf]

Take a little off the barrel and a little off
the spring...instead of all off one ...just a
guess.... wulf

 

[Stophel]

Mine almost always at least touch the barrel and require some clearance, though usually I don't need a big notch. Sometimes I do, though.

 

[Eric Krewson]

I panicked when the main spring on my first build came in contact with the barrel.

I read several solutions and ended up draw filing my main spring to narrow it. I took a good bit off(1/16") and went from a 30# spring to a 16# spring which I actually liked much better, real easy on flints.

Seems like Barbie Chambers said on one post to file the spring, sand it with progressively finer grits of sand paper and polish the area you filed to a mirror finish. I did this with the final result of no contact with my barrel and a great functioning lock.

 

[matt denison]

"... a pretty wide barrel...1 1/4" at the breech"


That's a real fat barrel. You should be able to remove material from the barrel no problem and leave the main spring alone. That's what I would do for what it's worth.

 

[Stophel]

Notching the barrel is S.O.P. on old guns. Not uncommon at all. :wink:

 

[twobirds]

Thanks, friends. This lock has a REALLY strong mainspring. In the past, I've worked a little of the thickness of mainsprings to lighten them, rather than reducing the spring width...but I think I'll take a little off the width, lower the lock placement, and then notch the barrel if it still touches. Thanks again! :hatsoff:

 

[Stophel]

You can only lower the lock so much. You need to keep the nose end of the lockplate in the right position to have the front lock bolt pretty close to centered. :wink:

 

[matt denison]

Just a warning.

If you modify the main spring to get the lock to fit then you will have to modify any replacement that ever goes in that gun. Many obvious and not so obvious problems can be avoided by simply taking a little off the barrel. No moving the lock up or down, no chance of missing the web with the front lock screw. It's a very common thing to do. With your big fat barrel you aren't creating any safety problem unles it is an 8 bore or something.