Acceptable gap between barrel and bolster?

[Blacktail]

I've got my lockplate inlet down to the point where I can barely fit a piece of paper between the lock bolster and the barrel. What is best here? Should I call it good, or keep going for the tightest fit possible?

[smart dog]

Hi Blacktail,
No gap whatsoever.  The bolster should snug up against the barrel touching at all points.  Any gap, no matter how small, may allow flash from the pan to invade the lock mortice.  That may char the wood or worse, smolder, turning your priming horn into a hand grenade.

dave

[Blacktail]

Thanks. I kind of thought so but then started second guessing about being too much of a stickler. It's just about there then.

[E.vonAschwege]

As Dave said, there shouldn't be the slightest gap at all - you should have the bolster completely tight against the barrel.  Definitely no shortcuts here 
-Eric

[ShutEyeHunter]

+about 10.  In addition to the minor ;-) problem of blowing off the lock, you want the lock bolts to clamp the bolster against the barrel..  Otherwise you're relying on compressible wood to hold the lock in place.  Lots of force in a lock and it needs something to connect to other than wood

Over time, the wood will compress until the lock finds the barrel anyway.  You might as well have it end up where you want...

I use inletting black (Jarrow's IIRC in the gold color from Brownells)'to get a 90% fit bolster to barrel (or recoil lugs on center fire rifles)

Note that you want a flat fit where the bolster is completely in contact with the barrel vs. just a line fit at the top.  Otherwise, the lock screws won't be pulling the lock at the right angle. 

See Beuchle/Shumway/Alexander for some examples

[Blacktail]

Thanks guys. I knew this had to be a big deal, but looking in both the Shumway and Alexander books, I failed to see where it was stressed much so that got me thinking. I'm once again reminded that the last few 16ths of an inletting job drive me nuts.

[Gaeckle]

You can reproduce the pulling affects of the lock screw by the use of a c-clamp. Place the clamp where you would normally have the lock bolt at and tighten down. Use inletting black or some other marking agent. You'd be surprised to see what else you may need to do as far as inletting is concerned.

[Acer Saccharum]

You can reproduce the pulling affects of the lock screw by the use of a c-clamp. Place the clamp where you would normally have the lock bolt at and tighten down. Use inletting black or some other marking agent. You'd be surprised to see what else you may need to do as far as inletting is concerned.

That is a GREAT tip, Gaekle. I never thought of that.

I mate the bolster of the lock to the flat of the barrel. You can file the bolster OR the flat to get a good fit. Use hi-spot blue or the inletting black to show where the contact points are. File accordingly. Maybe this is too anal for some, but my lock mortices stay nice and clean. No water or powder enters the lock mortices.

[Blacktail]

That is a good tip! And also a good point by Acer. I woke up in the middle of the night and it occurred to me that I need to check the bolster surface with a straight edge due to make sure I can get good contact. I plan on using an outside caliper to determine my lock bolt placement. Does anyone else do this?

[Gaeckle]

I forgot to add that the use of a c-clamp if over tightened will flex the lockplate, so you need to be a bit judicious in using this so as not to have a binding affect on the moving parts of the lock internals....it's a touch and go sorta thing. The c-clamp can also be placed at the point of the bolster conatct area. Often I use two: one at the point of the intended rearward lock bolt and then one at the front (which means the frizzen spring will need to be removed).

As I said, the use of the clamp can cause problems if one really cranks like a mad gorrilla on them, so it takes a bit of fore thought before putting them to use.