Mainspring edge hitting barrel

[DiMarco_Mercantile]

Hello,
I recently acquired my first flintlock rifle, and noticed there was a gap between the pan and barrel, maybe a 16th to a 32nd wide. I thought the lock just wasn’t inlet deep enough, but turns out it was the mainspring coming into contact with one of the bottom faces of the barrel! Photos attached. What would be a better method of solving this, filing down that edge of the mainspring, or filing down this particular section of barrel? I imagine it doesn’t matter too much, but thought I’d ask the experts! Thanks!

 

[Phil Coffins]

I would very lightly file the top corner of the spring. Remove the least amount possible.

 

[Hatchet-Jack]

I agree with Phil. Good job troubleshooting the issue.

 

[PathfinderNC]

I’m not a gunsmith, nor do I play one on TV, but my gut tells me to leave the spring alone and grind away the part of the barrel that it’s hitting, if it’s not a lot.

 

[rafterob]

Phil has given sage advice.

 

[tallpine]

I’m not a gunsmith, nor do I play one on TV, but my gut tells me to leave the spring alone and grind away the part of the barrel that it’s hitting, if it’s not a lot.

This is what I do. Commonly seen on original rifles, usually does not take much to get the spring to clear.

 

[waksupi]

Yep, grind the barrel. One of the few acceptable uses of a Dremel tool on guns.

 

[TDM]

I agree with @Phil Coffins, carefully and evenly file the mainspring. Check the clearance often. And polish out the file marks when finished.

 

[Flintandsteel]

Leave the spring alone, file a notch in the barrel.

 

[TDM]

Hello,
I recently acquired my first flintlock rifle, and noticed there was a gap between the pan and barrel, maybe a 16th to a 32nd wide. I thought the lock just wasn’t inlet deep enough, but turns out it was the mainspring coming into contact with one of the bottom faces of the barrel! Photos attached. What would be a better method of solving this, filing down that edge of the mainspring, or filing down this particular section of barrel? I imagine it doesn’t matter too much, but thought I’d ask the experts! Thanks!

After looking closer at the photos I'd draw file that barrel side to clean it up, it would bug me having the dings and dimples in it. So you might gain 2 or 3 thousandth there. Then take the rest you need of the foot of the spring. That's not a critical area, but you still need to exercise care and polish it afterwards.

 

[Art Caputo]

I would file the spring. Prior to doing this I would confirm that the spring is properly seated/fitted to the lock plate.

 

[SDSmlf]

Hello,
I recently acquired my first flintlock rifle, and noticed there was a gap between the pan and barrel, maybe a 16th to a 32nd wide. I thought the lock just wasn’t inlet deep enough, but turns out it was the mainspring coming into contact with one of the bottom faces of the barrel! Photos attached. What would be a better method of solving this, filing down that edge of the mainspring, or filing down this particular section of barrel? I imagine it doesn’t matter too much, but thought I’d ask the experts! Thanks!

Agree with others that one could possibly correct things by removing material from the barrel, but before doing that, price the replacement cost of a new barrel vs a new spring. It has been pounded into my head over the years to always modify the least expensive or easier to replace component. In this example, the spring. A 1/16” is a lot of material to remove from a barrel to get a spring to fit, especially in the breech area. I’d order a replacement spring if it makes you feel better, and once in hand, modify the spring to fit, leaving the barrel alone. Just make sure that you don’t leave any rough or sharp edges on the spring (aka stress risers) to create a potential weak spot in the spring.

 

[Hatchet-Jack]

That area of a mainspring can be altered to clear the barrel with no affect on the lock's function. Look at this example below. Look at how much metal has been removed for clearance.

 

[FlinterNick]

Many mainsprings are chamfered / beveled in that spot to avoid contacting the barrel and stock. I’d go with Phil’s advice. But you may need to reharden and temper the spring. I always do after working on a spring, file marks create stress points.

 

[TrophyGuy]

I am neither a gunsmith not a metallurgist, but a retired mechanical engineer. Given this choice I would make a relief cut on the part that operates undeflected with no special heat treatment, the barrel. There is gross excess material in the barrels to withstand pressure. Were this not true barrels would be bursting at touch holes and dovetail cuts. Thinning the spring's cross section will decrease its spring constant (maybe not much depending on the material removed), and decrease that delicate balance of spring forces between cock and frizzen. Your next post might ask why the lock doesn't spark or why the spring fractured in the return bend.

 

[FlinterNick]

I am neither a gunsmith not a metallurgist, but a retired mechanical engineer. Given this choice I would make a relief cut on the part that operates undeflected with no special heat treatment, the barrel. There is gross excess material in the barrels to withstand pressure. Were this not true barrels would be bursting at touch holes and dovetail cuts. Thinning the spring's cross section will decrease its spring constant (maybe not much depending on the material removed), and decrease that delicate balance of spring forces between cock and frizzen. Your next post might ask why the lock doesn't spark or why the spring fractured in the return bend.

I would not touch the barrel flat, it’s very easy to remove too much barrel and be stuck with a gap which is a critical mistake.

The spring can be replaced if it breaks, if too much barrel is removed, it can not be added back on with a weld.

I would file a chamfer on that spring, it will not detract from its performance in that spot, I’ve done this before.

 

[satwel]

File metal off the edge of the mainspring in small increments until the pan sits tightly against the barrel. I've done this on two of the rifles I have built. You don't want to mess with the temper of the spring by overheating it so file by hand. Do not use a grinding wheel or belt grinder. A gap of between 1/16 to 1/32nd will not require much filing to close. A thin coating of lipstick on the edge of spring will show you were it's touching the barrel.

 

[FlinterNick]

File metal off the edge of the mainspring in small increments until the pan sits tightly against the barrel. I've done this on two of the rifles I have built. You don't want to mess with the temper of the spring by overheating it so file by hand. Do not use a grinding wheel or belt grinder. A gap of between 1/16 to 1/32nd will not require much filing to close. A thin coating of lipstick on the edge of spring will show you were it's touching the barrel.

Agree, file by hand to avoid over heating the spring. Polish out any file marks, it will file with reluctance.

 

[Larry (Omaha)]

Hello,
I recently acquired my first flintlock rifle, and noticed there was a gap between the pan and barrel, maybe a 16th to a 32nd wide. I thought the lock just wasn’t inlet deep enough, but turns out it was the mainspring coming into contact with one of the bottom faces of the barrel! Photos attached. What would be a better method of solving this, filing down that edge of the mainspring, or filing down this particular section of barrel? I imagine it doesn’t matter too much, but thought I’d ask the experts! Thanks!

The spring, is where you attact the issue. Keep your bare hand on the spring to grind, and when it starts warming your hand, quench in water, then continue. If it turns blue or burns your hand, you may have ruined the temper. All surface cuts/grooves need to be parallel to the length of the spring and polished out. A right angle to the length, scratch/groove can cause fracture when the spring flexes.
Larry

 

[FlinterNick]

The spring, is where you attact the issue. Keep your bare hand on the spring to grind, and when it starts warming your hand, quench in water, then continue. If it turns blue or burns your hand, you may have ruined the temper. All surface cuts/grooves need to be parallel to the length of the spring and polished out. A right angle to the length, scratch/groove can cause fracture when the spring flexes.
Larry

I would not use a bench grinder on a tempered spring.

I’ve made plenty of springs, fitted them to locks. I’d use a smooth file and then polish it back with an emery pad or paper. You’ll find that you likely don’t have much to remove.

I only use bench grinders for removing casting gates on annealed steel parts or brass.