Barrel-Lock repationship

[James Tenaglia]

Would anyone with knowledge and experience care to write a description, explanation, synopsis, (or even dissertation) re: the relationship between the size of the barrel at the breech and the size of the (flint) lock, especially as it relates to mainspring clearance of the barrel?

[Acer Saccharum]

I've had locks where the mainspring interfered with the angled flat on the barrel.  I was able to grind a little fact on the top leaf of the spring to get it to nest properly against the barrel. I have seen barrels that had a a mortise cut in them to accept the spring. This is OK to do if the barrel has plenty of wall thickness.

Mostly one has this problem when using a lock that is too small for the barrel. I really don't have a rule of thumb that I use for this.

Before you start laying out, or making a drawing of you gun, place the lock on the barrel in the orientation you desire. If the spring hits the barrel, you will know you have to bevel the spring a little, or get a bigger lock.

[Bob Roller]

I've had locks where the mainspring interfered with the angled flat on the barrel.  I was able to grind a little fact on the top leaf of the spring to get it to nest properly against the barrel. I have seen barrels that had a a mortise cut in them to accept the spring. This is OK to do if the barrel has plenty of wall thickness.

Mostly one has this problem when using a lock that is too small for the barrel. I really don't have a rule of thumb that I use for this.

Before you start laying out, or making a drawing of you gun, place the lock on the barrel in the orientation you desire. If the spring hits the barrel, you will know you have to bevel the spring a little, or get a bigger lock.

Lynton McKenzie had a Fenton target rifle,English made,16 bore with double set triggers and a tiny lock of pocket pistol size.I copied this lock using external castings from an English foundry and notice the pan/bolster area was a bit wider than usual and I assumed it was for mainspring clearance on a barrel about 1-1/8" at the breech. Lynton and Steve Alexander (I think) copied the original gun for a customer and Steve did the lock on this one and did a superb job. I did a good job on the one I made but Lynton's engraving put Steve's over the top. I don't remember who got mine and the man who has the McKenzie/Alexander copy will remain anonymous.

Bob Roller

[David R. Pennington]

Going the other way, an overly large lock on small barrel, mainspring can crowd the ramrod.

[jerrywh]

 The size of the lock is not as important as the position of the spring on the plate.  If you look at high quality flint locks, especially English locks, you will notice that most of them have a leg on the top leaf where they anchor up under the pan. Even in the absence of the leg the spring sits low down on the plate and usually has a bevel on the top leg to give clearance for the barrel.  The bottom leaf may also be beveled in order to balance the two leaves for strength.    The main thing is to have the spring low down on the plate.  The lock below would be for a large bore English sporting rifle. Those guns had very large barrels and this is how the English gun makers dealt with the problem.  No one was better.

[Jerry V Lape]

I know one thing about this subject I hope to never repeat.  Used a lock  very similar to a small siler on a 1 1/16" barrel at breech end.  It eventually worked out but I had initially tipped the nose of the lock upward just a little (not on purpose).  As a result the mainspring was in contact with the barrel when it didn't need to be.  Little fudging here and there and a little beveling of the upper arm of the mainspring solved the issue.  The lock had a very wide upper mainspring which the maker had not beveled at all which did not help.  I like to have the lock inlet contained - not break through the wood into the barrel channel.  There was no way to do that on this one.  And I have been told by a respected builder that there are more originals with the mainspring through the side of the barrel channel than not. 

[James Tenaglia]

Thank you for the educational responses. This area of building deserves attention when planning a longrifle so as to avoid or at least mitigate some of the pitfalls mentioned in some of the responses.