Correcting an arbor fit issue on my 1851 Colt Navy.

[Flint]

I have replaced the pin, when removing /replacing an arbor with a #6 set screw, which is easier to remove, if necessary, at a future date.  David Chicoine's recommends in his book a #6-48, but a #6-40 or #6-32 is easier to find in the hardware store.

[Mako]

I have replaced the pin, when removing /replacing an arbor with a #6 set screw, which is easier to remove, if necessary, at a future date.  David Chicoine's recommends in his book a #6-48, but a #6-40 or #6-32 is easier to find in the hardware store.

Not a bad idea, but I'm not sure you will be able to tap a coarse or even a fine threaded hole half in steel and half in brass.  Drilling would hard enough.  The factory must have a guiding jig and use a very drill bit with very flat angle flutes or even a tapered mill  to keep it from pushing off into the brass.

A 6-32 is normally preffered in a soft metal to maximize the engagement of threads in the material more prone to stripping out.  In this case a 6-48 which is an Extra Fine Thread might work better.  You can get them and the taps at Brownells. 6-48 is one of the more common "gun" threads because you get more threads for shallow holes you commonly encounter.  I'm not sure how the tap would act in that hole, they are stiffer than drill bits and if he used a taper tap instead of even a plug tap it would probably guide the tap and stop it from pushing off as much. 

Now that he has a starter hole he could choose to ream it I'm not sure I would try to drill it.  The drill bit will push off and the outer flute corner will just cut into the brass. 

~Mako

[Mako]

Ah. That makes sense as all it has to do is lock the arbor from turning, right?

So if I'm going the extra safe route, and creating a form, what do you recommend for a filler in the form? JB Weld? Some form of epoxy? How much percussive force does the arbor actually take in the process?

RT,
It probably sees minimal force under recoil, even if it did it would be in compression.  Anything you added would have great strength under compression, it is the shear and peel loads that are problems with any epoxy.

JB Weld is just a metal filled epoxy.  I'm assuming you are talking about adding it to the end of the arbor and not to take up any slop in the threads where it goes into the frame.  If you want to add length you might need to add a small hole on the arbor end to assure you have a good grip on the epoxy.  I enclosed a sketch below to show you what I mean.  I am not saying you should do it, I'm just showing one possible fix.  If it were up to me and the arbor was already removable I'd weld it up on the end and then turn it to length on a lathe.

Regards,
Mako

(Someone PMd me and told me and told me they couldn't open the PDF file so I will include a JPEG, use the PDF if you can, it has better resolution)

Click on the PDF file below to open the drawing up.

[RollingThunder]

Yes, I was figuring on adding it to the muzzle-end of the arbor, that way there is no re-positioning issues with the wedge.

So the DevCon putty you mentioned in the drawing ... I am assuming that is the same LeakStopper stuff that's about 5 bucks at the hardware store, or a different kind of DevCon putty (I know there are some others out there).

This is highly informative, by the way, thanks for sharing your knowledge!

[Mako]

Pettifogger,
I agree, I think it would be thinner than I would like.  I've always welded them up, that was primarily for illustrative purposes...

By the way, I've really enjoyed your articles, I'm looking forward to the next one.  I think it really drives interest in the Chronicle when good pieces like that are run.  I remember back in the “old days” (the late 70's) when American Handgunner ran instructive pieces (but not on C&B revolvers) by men who ended up in the founding group of the American Pistolsmiths Guild.  That’s when the magazine was actually useful.

If you ever need some illustrations just PM me, those are actually two solid models and an assembly, not perfectly to scale but close enough to show what I was talking about.  I did it while eating a sandwich, it took less than 30 minutes.  I think Flint has a bunch of models he’s already created, I remember seeing a couple that were posted a while back.

Regards,
Mako

[RollingThunder]

PDF (Portable Document Format) allows the embedding of any vector or raster based file. Vector means that a line is drawn between a set of coordinates in a file. Once the line is completed (as in a square, etc.), you can fill the bounded area with a color, a gradient, a masked raster/picture image (that's how we get textures on 3D images). Raster means the same line is drawn with a one-pixel square, colored box. 

When you expand a vector illustration, because it is drawing coordinates and lines and filling them usually with a solid color or gradient, you lose no edge clarity.

When you expand a raster image, you will lose edge clarity because a pixel does not adjust to the view-size, and the more you zoom in on it, the larger it will appear, until you end up with a bunch of little squares where there should be a smooth straight line.

[rifle]

Rolling Thunder, I tried to answer your question in some detail over there at the Open Range. There's more to bottoming an arbor than gets mentioned here. There's the cylinder gao to attend to and that may result in the barrel being set back and maybe the arbors slot being welded and a new wedge fit.
"Easier said than done", comes to mind here. You can open Pandoras Box here bottoming an arbor espesially with a gun that really wasn't machined with good tolerances to begin with.
The quick fix isn't Epoxy in my opinion. Guns are steel and should be fixed with steel or some other metal.
Shims can be made from shimstock bought from machine shop supply houses. MSC is one. Shims for cap&ballers can come from an old pie pan too. The kind I lke are copper from that craft thing where people punch holes in a sheet of copper to make a picture. Nice sheets of copper.
The shims of copper or aluminum usually fit unless the space is just too small and a regular shim "so many .001's thick" is bought from a supply house.
The softer than steel shims(steel shims can be used too) let them form fit when they are made a little too tight for the space of the hole. A simple matter of cutting the shim with scissors and the wider it is the tighter in the hole and the thinner it's cut the more loose. The shim goes on top the arbor above the wedge slot. Held with a small screw driver while the barrel is inserted so the shim goes in with the arbor. making the shim a little tight and using a rubber hammer to tap the barrel on form fits the shim of softer than steel material so there's a perfect fit.
It's easy to do once you get the hang of it.
The arbor being "tight" in the arbor hole is as good,I say better, of a mechanical fit than a bottomed arbor. If you think about it from a mechanical point of view you can see why.
Anywhoooo....go to the Open Range and see what I took the time to type with my two fingers. It explains some of the aspects of bottoming an arbor that usually aren't mentioned when people try to explain the methods they use. The cylinder gap and the resulting fit issues with the barrel,wedge,arbor slot ect.ect. are mentioned in what I tried to explain.
People explain bottoming arbors and leave the details of the resulting issues that can come up out probably because of the typing amount and the complexity of trying to explain the issues.
Think....you bottom the arbor real nice....then the cylinder gap is real wide. What now?  ha ha ha 

[Mako]

Rifle,
I’ve read your post three times over a three day period hoping it would make more sense to me if I let it sit for a while.  I’ll tell you I must be a bit slow, but I don’t know what the difference would be between adding a filler material of weldment or even epoxy or a shim.  I guess shims are easier and more easily reversible, but they are also easily lost.   Even went and read your post on The Open Range Forum.  I then realized you were talking about side shims… I think you’re making this way too complicated.  If you have an open top revolver that can have the cylinder gap set to the correct cylinder gap without having to drive in a wedge with a hammer (meaning hard blows, not light tapping), then you have the ability to take up the space between the arbor and the hole end.

The statement that had me buffaloed is this one

“There's more to bottoming an arbor than gets mentioned here. There's the cylinder gao(sic) to attend to and that may result in the barrel being set back and maybe the arbors slot being welded and a new wedge fit.”

  Why would you do anything to change the cylinder gap if you can currently insert the wedge and already have your gap the width you want it?  The whole point is to put material in an area where there isn’t any, not change your barrel gap.  The material added to the arbor is to add a hard stop to give you a consistent barrel/cylinder gap and to prevent movement that wears the arbor, barrel, wedge fit out.  If you add more than the gap between the end of the arbor and hole in the barrel underlug then you would change the spacing out.  If you add less then there would be no effect. 

Slip your barrel without a wedge on the arbor (with or without the cylinder) and then look through the wedge slot perpendicular to the bore axis you should see the front of the Arbor Slot sticking back into the Barrel Slot.  This means the Wedge will engage on the front edge of the Arbor Slot and the back edge of the Barrel Slot.  If it were the other way around you could never pull the barrel tight, there would also be a gap where the frame meets the barrel underlug. If you had the cylinder in place you could use feeler gages to determine your cylinder gap without the wedge.  I read your recommendation of an “ideal” .006” gap on the Open Range post, I disagree with that…  That number is for smokeless powder revolvers.  I actually set my BP percussion pistols between .010” and .012”.  The Colt shop manual for SAAs specifies .008” as ideal and that is for smokeless powder revolvers.  The “perfect” fit CAS percussion revolver for me would gage .013” without a wedge and .011” with one in place (that is with a modified arbor on a Uberti or a better fitting Pietta).

You can easily determine how much space you have between the end of the arbor and the bottom of the hole in the underlug.  You put the barrel on the arbor, but instead of lining it up you rotate it to either the right or left of the end of the frame then measure the amount the barrel underlug goes past the end of the frame.  That is the amount of material whether it be shims, weldment  or anything else needed to be added to take up the space.

Why would that change your cylinder gap?  If your barrel gap was .012-014” without a wedge it couldn’t close up less than .010” with the wedge in place.  That’s what the material on the end of the arbor does, it sets the minimum gap.  It better NOT widen your gap, because that would only happen if your wedge slot was already off, the barrel would already be pushed forward.  If the wedge pushed the barrel out in the slot you would open up a gap between the frame and the barrel lug which would be very obvious.  If you start with a gap greater than .014” and collapse it more than .004” then you have a problem with your lug to frame contact, meaning your barrel extension at the rear is too short.  This happens sometimes because someone tried to correct a non-square barrel to cylinder gap.  This is almost always caused by a poorly fit barrel and someone who doesn’t understand the barrel, cylinder, wedge and frame fit relations.  They go after the back of the barrel with a file.  If they had just not hammered the wedge and fit it to allow a square engagement  it would probably have been the correct length.

Adding shims to the sides of the arbor as you have described is just wedging material in the clearance between the sides of the arbor and the hole (not the end) to wedge it a second time.  So now you are just wedging the barrel between the wedge and the shims you have added.  As you said they loosen up and as soon as you remove the barrel for cleaning you may or may not get it all back.

My wedges are set so that I press them out (not even tapped or hit) with a wooden stick and then when replacing them I lay the Starboard side of the barrel slot on a softy pine board I carry in my loading box (or the bench) and push then tap the wedge with a small stick of wood (½ X 1 X 6 inches) until it bottoms out on the wood.  This leaves the wedge spring hook barely engaged (which is how I run my wedges).  But I set them to a consistent depth.  On my competition pistols with fit arbors, the wedge won’t go in any further than the hook (unless I took a hammer to it).

I have several pairs with modified arbors and more without.  If I am going to use them in competition I usually shoot then a bit then get my wedge engagement and cylinder gap correct.  I also watch for tight spots, make sure the cylinder is running square and without ratchet or back bearing surface problems.  Then weld up the arbor and use a surface grinder to set it to length. I could also mill it or simply use a file held square.  If you do the Arbor first you might have to redo it after the cylinder is a fully regulated. 

You could do exactly the same thing with JB Weld or shims at the bottom of the arbor hole.  In fact someone who is doing it for the first time could make shims out of any light gage metal including cans and find the thickness that works before welding or adding JB Weld.  Then they would have a number to cut the added material to.  The problem with shims is getting the in between thicknesses.  Unless you are simply lucky or want to sand a shim thinner you would need a package of shim stock in various gages.  Remember what I said earlier, if it doesn’t  bottom out it serves no purpose.  It’s sort of like water, once it’s over your head it doesn’t matter if it’s 8 feet deep or 5,000 feet deep.  Once you are too tired to bounce off of the bottom you’re probably gonna drown.  A .002” gap with the wedge fully engaged isn’t really any different than a .200” gap (arguable, but for the sake of illustration please grant me that).

Regards,
Mako

[rifle]

Howdy Mako, I'll try to answer the question you seem to be asking about the arbor bottoming but specifically the cylinder gap area.  I think this part is misunderstood by many. The looseness in the arbor hole with the arbor in it seems to almost always be along the top of the arbor. When the barrel is drawn back by the wedge the bottom lug of the barrel stops at the frame but the top breech end of the barrel doesn't stop even with it. The breech of the barrel keeps going back closing the cylinder gap abiet unevenly. The gap gets closer at the top of it and wider at the bottom of it as you observe from the side seeing light come thrrough. That's because the force of the wedge has to go somewhere and the path of least resistance is anywhere there's space. The space is at the top of the arbor and is seen at the top of the barrels arbor hole. The barrel can't go anywhere at the bottom lug since there's no space there if the barrel is against the frame. So as the space is closed at the breech area with the barrel canting downward at the breech end and naturally upward at the muzzle end until the top of the barrels arbor hole right at the beginning cants downward until contact is made by the top of the barrels arbor hole at the very beginning with the top of the arbor. That contact point and the space there being closed up then the barrel stops moving. You know...like the barrel pivots at the frame/barrel point stressing the frame pins when those holes in the barrel take up any space that's there and the pins can flex some until the space at the top of the arbor hole at the beginning of the barrels arbor hole is closed and the barrel is in contact with the top of the arbor there. That rocking or canting of the barrel after the barrels bottom lug contacts the frame is the movement that eludes a lot of people.
The guns that have more space in the arbor hole than others also shoot higher than the others with less space. Also the guns with the most space in the arbor hole of the barrel when the arbor is in there have a cylinder gap wider at the bottom and naorrower at the top of it. Take Ubertis for example....the ones people say they have to set the cylinder gap with a feeler gauge at each assembly. Those have more space at the top of the arbor hole and they can more easily have the wedge force close the gap and pinch the cylinder and stop it from moving. The Piettas then....have a more snug arbor hole for the arbor to fit in and the minimal space is taken up and the top of the barrels arbor hole at the very beginning males contact with the top of the arbor and the barrel stops moving much sooner. It isn't only the bottomed arbor the Piettas have that sets the barrels rock solid and the wedges stop with a certain authority that can't be mistaken.When the wedge is driven into a Pietta Colt(the ones that are right from the factory) it goes so far and stops rock solid and it's real easy to tell it aon't going any further...doesn't cant enough to notice and doesn't pinch the cylinder and the cylinder gap is uniforn at the top of it and the bottom of it(at least uniforn enough it would be difficult to measure with a feeler gauge).
Anyway if a person doesn't realize the barrel is drawn back by the wedge with that tightening the barrel/frame contact but the breech part still moves until the top of the arbor hole space closes until the barrel at the top of that hole contacts the top of the arbor then it's difficult to fully understand the fit of a Colt type gun with a wedge and all. If a person doesn't realize there's movement by the barrel after the barrels bottom lug meets the frame they don't have the full picture. It's easy to miss I guess.
Take a Uberti since they are good examples......set the barrel on and push it rearward as far as you can....put pressure on the barrel as if you were trying to bend the barrel muzzle upwards and watch the space between the breech and the cylinder and the space between the top of the arbor hole in the barrel and the top of the arbor. When the wedge is out and you can move it by hand you can see it plain as day. If you can't believe the barrel cants upward at the muzzle and downward at the breech after the barrels bottom lug meets the frame then you won't ever see what's being discussed here.
You mentioned shim...and interprete myself talking about "side shims". No side shims. That would be kid of difficult with the wedge in there and all. I mention that a shim layed on the "top" of the arbor" and inserted with the arbor into the barrels arbor hole takes up the space there and seats the barrel much better and locks it better and the gun shoots less high ect.ect. Belgian Centenniasls and Piettas are examples. The Piettas or Centaure Centennials don't shoot as high out of the box as a Uberti(at least the older Ubertis since I can't talk about the newer ones I haven't seensince Beretta runs the show) because they have the arbor bottoms in the barrels hole and, in some cases also have a snug fit of the arbor in the barrels arbor hole. Optimum is a snug tap on or push on fit of the barrel on the arbor.
Mechanically speaking..if a barrel has a nice snug fit onto the arbor with "no space" in the hole,or very minimal, that is actually a better fitting than a bottomed arbor in the barrels hole. If a barrel is quite snug on the arbor with it's contact points being at the frame/barrel point and along the length of the arbor there's no where for the barrel to go once it stops at the frame/barrel point. It stops rock solid with no canting of the muzzle upwards and the breech downward.  Mechanically speaking the arbor real nice and snug in the barrels arbor hole is better than just a bottomed arbor with space between the top of the arbor and the barrel. Why?  Even with a bottomed arbor where the end of the arbor is perpendicular with the axis of the arbor and the bottom of the barrels hole is perpendicular with the axis of the barrel the barrel will still find a way to rock on the frame where the pins are until the space between the top of the arbor and the beginning of the hole is closed. It will at least stress the frame pins or let the pins move in the barrels holes or deform the pins ect.ect. untill the space between the arbor and the beginning of the barrels arbor hole is closed.
Anbywhooo......once it's all seen it becomes vdry simple. Like....crap...why didn't I see that before?     Even pro gunsmiths that are familiar with all types of complicated shooting machines can miss parts of the fitting of a barrel onto an Open Top Colt.
Anyway....if you put your barrel on your Colt and leave the wedge out and play with it and kind of move things around you'll see what I mean.
You will see that the perfect fit would be a very snug fit of the arbor in the barrels hole and a bottomed arbor in the hole See that the less space there is in the arbor holw when the arbor's in it the better and the bottomed arbor is only part of the fix. The space above the arbor being closed is as important as a bottomed arbor or maybe more so. The bottomed arbor is great but...without the minimum space between the arbor and the barrels hole the bottomed arbor is incomplete.
Anywhoooo.....so can see that the barrel still moves after the barrel meets the frame when the's a loose arbor hole.
Cylinder gap? I like to set those at .006-7 but sometimes .010 even. It's an opinion thing I guess as to what the optimum cylinder gap is. It matters what you do with the gun..Cowboy Shooting versas target shooting as an example. It depends on the gun too. I like the .006 but I gunsmith the guns for optimum accuracy which is just where my head is I guess. If I do a gun for someone and they are going to shoot "Cowboy Shooting" I'd be more apt to ask if they want a wider cylinder gap. A wider gap makes the standard diviations go up more.
Anyway....the shim of a softer than steel material(metal) is an easy fix. No need to bottom the arbor and all. Just get a shim in tight where you tap the barrel on with a rubber hammer(at least till the shim loosens up some which they do and need changed every so often after so many hundreds of balls fired. Maybe every 1,000 or 2,000 balls.) to form fit it. You know an aluminum or copper shim. If the shim is steel it will last a very long time but it has to be exactly the right thickness right off the bat.
It's actually better the go beyond the shim thing where the shim is cut with a pair of scissors and all and......
Put a dab of weld in two spots on the arbor. One where it wuld be just inside the beginning of the barrels arbor hole and the other neat the end of the arbor. File fit them to where the barrel goes on but goes on pretty snug. That is better than a shim that may get "lost" as you mentioned.
The dabs of weld on the arbor?........they can be used to get a gun shooting center instead of left or right or high or low to a certain degree  ect.ect. also.
Anywhoo....epoxy type stuff to fill the space where the arbor doesn't bottom? There's such a tremendous force emmitted by a wedge that it would crush the JB Weld or compress the epoxy. Wedges emitt a very large amount of force.  The end of the arbor needs to be steel or it will just not do what a bottomed arbor does....stop the barrel rock solid.......if the bottom of the arbor hole is perpendicular with the barrels axis and the end of the arbor is perpendicular with the axis of the arbor then the bottomed arbor helps the barrel be mounted straight and more solid and have less movement when the gun fires.
Movementwhen the gun fires? Yep but I ain't got the energy to type about that.   Lets just say that the frame pins fit in the barrel holes and the wedges  "fit" side to side and"top and bottom" are important to eliminate parts movement when the gun fires and important to optimum accuracy.
If a Colt gun is constructed or machined or fit together real well and proper it can shoot as accurately as any Remington cap&baller. Could be used as a target gun against Remingtons and Rodgers and Spencers ect.ect.
What you say?  That guy is freekin nuts?     
One thing..... 
Just remember I told ya......the optimum fit of a Colts barrel has no space in the arbor hole and the arbor is bottomed in the hole.
Before I go........someone mentioned that they bevel the end of the arbor to fit better because the bottom of the hole is concave. Not good to do. The part of the end of the arbor that does the best bottoming job is the outside edge of the arbors end. The outside edge of the end of the arbor contacts the outside edge of the bottom of the hole. It's better to leave the end of the arbor as wide as it can be to contact the bottom of the hole as wide as it can. The bottom of the hole....around the outside of the circle or the "corner" is where the contact should be. Maybe the very small edge of the arbor gets beveled when it's a tight fit in the hole if the "corner" around the bottom of the hole has a slight radius to it and not a perfect 90 degree corner. Anyway the contact point is or has to be right arounf the edge of the arbor and the edge or corner of the hole where the hole very begins. The contct can go inward further from the edge or corner naturally. Some guns have the edge of the hole reamed at a 90 degree angle with the wall of the hole and that makes a step around the circumference of the hole for the arbor with an end perpendicular to the arbor to sit on. The center part of the hole can still be concave though.
Some guns have the bottom of the arbor hole reamed where the bottom is all flat and perpendicular to the walls of the hole. Anyway...don't bevel the end of the arbor unless it's to let it fit better where the bottom of the holes corner has a slight radius to it.
The in-between shim thickness? If it is a problem then the end of the arbor can be filed a little. The shims if there's only one that you want in the hole and it's a little thick can be stoned down some.
There's nothing wrong with a shim in the hole. I wouldn't want to mess with several shims in the hole though. Anyway..the shim can be fit to the circumference of the hole so that it stays in and doesn't fall out or get lost. It can be made to fall out too if that's what a person wants.
I think if a person uses the method of pressing the wedge in my hand or by a wood dowel and leaving it like that then the wedge is too loose. The barrel would go forward with the first shots and tighten against the wedge but the gap would get a little bigger and the wedge may loosen upon firing multiple shots. The wedge tapped with a small hammer handle or block of hardwood can seast the wedge with the correct tightness so the wedge stays there right where it's set to.
We all have our different and personal methods of doing things. Some are "right" enough and some are "right on". If a person is satisfied with their proceedures then that's all that matters as long as the gun shoots good enough for them.
Welds spots on the arbor and "wedging" the arbor between them? That's the idea. That's what the walls of the arbor hole does if the arbor fits right and is snug.  Like in D. Chicoine's book,"Gunsmithing Guns of the Old West", he mentions that a snug push fit of the arbor into the arbor hole is a good thing.
Rotating the barrel on the arbor like is shown to see what type of bottoming space there is is a good thing. I post that from time to time for people. There's a little draw back though to that and that can't be used for a precise way to measure the amoung of bottoming needed. It's the looseness of the barrel on the arbor that causes a problem. You can move the barrel on the arbor and get two different measurements. The looseness of the arbor in the holes hole again........
You need a method that's more precise like using Prussian Blue(from Brownells)  on the end of the arbor to tell when it's bottoming with too much space between the frame and barrel. Then stone the shim till the barrel comes to within a .001 or .002 of the frame. The .001-2 leaves room for "seat in" that accures when the arbor slot end or the barrels bottom of the hole compress from the wedge insetrtion and the force the wedge emmits. Shooting the gun can deform the end of the arbor a little after awhile too so the .001-2 is like a backup.  Anyway the best way I've founf to bottom an arbor whether it be the actual end of a new arbor of a shim in the space is to get it close using Prussian Blue machinists ink (used like intetting blackening when working on wood) and seeing the gap between the barel and frame and then stoning the shim. Notice I'm saying shim and not shims. I like to end up with one shim in the hole so it can be tacked welded to the end if I want. It's cool to add material with welding and work that so when done the shim is actually the end of the arbor.  Also...using the machists ink you can see if the whole arbor end ,or the full circumference of the edge of the arbor,is in contact with the bottom of the hole and if not stone the end so it is in better contact(before the barrel reaches the .001-002 space between the barrel and frame). A softer steel shim used in the hole can be left a tad wide and the barrel wacked with a rubber hammer to sest the shim. If not that then when the wedge sests the barrel and the wedge emitts it's great force the shim will flow in where there's any space and the entire end of the arbor will be in contact.
Anyway...if you're going to build a "race" Colt then the first thing is to have a machinist make an arbor that fits with no space in the "reamed uniform" barrels arbor hole. Then go from there. Make a wedge that is in contact with the barrels slot and the arbors slot that should be perfectly even with each other side to side and "top and bottom". That "top and bottom" keeps the barrel from rotating on the arbor. The barrel will do that even if the wedge is really really tight. The whole barrel and wedge can rotate up and down on the arbor. Put the barrel in a vise and grab the grip and rotate side to side. The barrel usually moves on the arbor as does the wedge in the slots. That space has to be taken up so the barrel can't move on firing and bounce side to side and wear the wedge and stress the arbor and change the point of impact of the balls on the target. People have a hard time imagining the barrel held on with a tight wede moving but it does every time the gun fires if there's any space to the fit of the pars at all. Then the flexibility of the arbor and the steel parts(stele has memory)is the only movement which can't be helped unless the parts are re-made of very hard ordanance grade steel to minimize the movement.
Now I'm done I guess. Hope this helps someone so all this typing is not for nothing. Mako...if I didn't answer your questions then let me know which ones I didn't answer.

[RollingThunder]

In other words, if in the original non-bottomed fit, there is slop around the arbor (not on the arbor tip, but around the arbor), the barrel can still move up or down, and that of course changes the cylinder gap as it pivots on the bottom frame lugs. Pivoting on the lugs could move the barrel fore or aft from the cylinder. That movement (if any) is further affected by the wedge re-aligning the holes of the arbor and the barrel assembly. Any slop in the fitting of the barrel wedge assembly through poor machining, wear etc., means that even as the wedge sets the final angle of the barrel, there could still be additional rise or drop to the barrel, meaning you shoot high or low.

Once that is corrected with shims, and the barrel is now on the same angle as the cylinder, and shooting straight, there may have been a change in the cylinder gap. Using the example of a barrel that shoots high, the barrel that now shoots level has been moved forward, and away from the cylinder. The hand's pressure may not be significant enough to take up the slop and set the cylinder forward enough for an acceptable gap (an acceptable gap also being up for discussion, I assume).

If we further speculate, and say the new cylinder gap is unacceptable, then you also run the risk of, after increasing hand pressure to push the cylinder forward, changing the throw distance of the hammer, because the cylinder is now being pressed more forward, even ever-so slightly, and the hammer may be bottomed out to hit at a certain distance, to give the pistol a correct ignition on the cap.

Does that sound right?