So just how bad does a .015 gap look?

[RUSS123]

To some it may be acceptable, to other it's horrendous.

When I think of having such of gap I also think it's horrendous and to correct it would seem like an impossibility without frame shaving but that was just my imagination. I had my digital caliper out the other night to check my cheap automotive feeler gauges for accuracy because I had used them to conclude the gap on my 1872 was way too much. Visually, a gap .012" appeared to be far worse on the gun itself than it did on my caliper and that puzzled me. I thought I had made a gross error in measurement with my feeler gauges.

Looking at a .015" gap set on my caliper now, I was surprised at just how minute it appears. That's it, really? I expected the gap to be visually much wider but was my imagination on overdrive. I said to myself,  "you don't need to cut the frame back for that tiny little amount of space. I still wonder why a B/C gap of only .012" looked so bad on the gun itself. Optical illusion?

What I want to say is:  I can't see how I ever thought you would need to cut the frame to help close this gap but I did think that. I take it back. And yet, you are really only needing to move the barrel in closer 1/3rd less than this....

Here's what .015" looks like.... next to nothing!

[Abilene]

My 1st gen (1901) .45 SAA has a BC gap close to that.  I've shot a couple thousand rounds through it with no problem (mostly BP).  Probably losing a little velocity, who cares?  But the outside of the cylinder does get really dirty fast.

[RUSS123]

My 1st gen (1901) .45 SAA has a BC gap close to that.  I've shot a couple thousand rounds through it with no problem (mostly BP).  Probably losing a little velocity, who cares?  But the outside of the cylinder does get really dirty fast.

It's just dirt!  I've come to realize that endshake is far more important than a whatever the BC gap is. You can have a huge BC gap while keeping endshake to a nearly zero by virtue of a bushing! On a cap gun, the BC gap is your endshake, no bushing, unless someone wants to try and incorporate a bushing. I wonder if anyone has ever thought of that?

The .015" gap I'm showing with my caliper is the endshake (Im2bent) needs to get closed on his Dragon when correcting his Arbor length. He only really needs to close about 2/3rds or .011" to achieve an acceptable "endshake". It's not going to require removing anything off the frame due to a radius fulcrum factor at the frame pins. The needed rearward movement of the barrel towards the cylinder is just too small.

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[greyhawk]

It's just dirt!  I've come to realize that endshake is far more important than a whatever the BC gap is. You can have a huge BC gap while keeping endshake to a nearly zero by virtue of a bushing! On a cap gun, the BC gap is your endshake, no bushing, unless someone wants to try and incorporate a bushing. I wonder if anyone has ever thought of that?

The .015" gap I'm showing with my caliper is the endshake (Im2bent) needs to get closed on his Dragon when correcting his Arbor length. He only really needs to close about 2/3rds or .011" to achieve an acceptable "endshake". It's not going to require removing anything off the frame due to a radius fulcrum factor at the frame pins. The needed rearward movement of the barrel towards the cylinder is just too small.

Russ
something I missed first time round in Mikes notes was ..... his suggestion for some careful filing to square the forcing cone to the
(adjusted) cylinder gap then a little extra off of the arbour button to compensate. Its the other way of doing it and leaves the locating pins undisturbed  and the frame/fulcrum square and true. Took me a while to get that and I can see why
That said ..on an old gun with 15 to 25 thou gap I would probably opt for clipping the frame some. I like the idea of keeping the line of the bore as true as possible to the cylinder and arbour. the machining more tricky though.

[45 Dragoon]

Russ
something I missed first time round in Mikes notes was ..... his suggestion for some careful filing to square the forcing cone to the
(adjusted) cylinder gap then a little extra off of the arbour button to compensate. Its the other way of doing it and leaves the locating pins undisturbed  and the frame/fulcrum square and true. Took me a while to get that and I can see why
That said ..on an old gun with 15 to 25 thou gap I would probably opt for clipping the frame some. I like the idea of keeping the line of the bore as true as possible to the cylinder and arbour. the machining more tricky though.

Greyhawk thanks and your assumption is correct about leaving the frame/bbl lug alone. In this instance though, the excessive clearance was created from a "too thick button" to begin with. The OP stated that it is a new revolver. The wedge can be  driven in enough to lockup the cylinder.  That being the case, you only need enough material (button, spacer, ) to hold the barrel at your desired spec.  Trying to "align" the frame/ bbl lug isn't the place to start.
  As far as barrel/frame alignment, adjusting for a .0025" - .003" (my spec.) or any of the others mentioned (don't know why anyone would want anything more than .004" but  .  .  .  what ever .  .  . ) is not going  be any significant movement. In any case, it will be the same form now on .  .  .  once sighted in, you're done.

Mike

[RUSS123]

.....on an old gun with 15 to 25 thou gap I would probably opt for clipping the frame some. I like the idea of keeping the line of the bore as true as possible to the cylinder and arbour. the machining more tricky though.

This is such a great discussion!

I would certainly agree with keeping the line of the bore as true as possible to the cylinder and arbor but that's assuming the bore alignment is true to begin with. I'm sure there's a special tool to verify that. What I see is: The arbor fits into its hole that is drilled into the barrel assy. The cylinder chambers will remain in line with the arbor but what if the hole for the arbor is off a slight bit. The bore alignment to the cylinder is then dependent on the precision drilling of the arbor hole in the barrel assy. That's a real possible error I see but what do we have to verify that?

With all that said and for what I can tell without written specifications, there's an equal possibility that the bore alignment may become improved when all is said and done. Crazy I know! Mike says there's not going to be any significant movement. I'll take Mike's experience to the bank.

.015" is such a tiny space to work with here. I can see a potential that if you accidently over cut the frame, the arbor could then become a fulcrum and the frame will lack sufficient tension with the arbor to ensure an all around solid union. I believe that was also something Mike was alluding to as well. I feel sure you would want some tension at the frame as well. That said, I'm sure there's a point, if the gapping were so great, you would have no choice but to cut the frame or try a new barrel assembly. I only say these things out of intuition, not experience.

I came from the 1911 Forum where everything was about specification.

[greyhawk]

This is such a great discussion!

I would certainly agree with keeping the line of the bore as true as possible to the cylinder and arbor but that's assuming the bore alignment is true to begin with. I'm sure there's a special tool to verify that. What I see is: The arbor fits into its hole that is drilled into the barrel assy. The cylinder chambers will remain in line with the arbor but what if the hole for the arbor is off a slight bit. The bore alignment to the cylinder is then dependent on the precision drilling of the arbor hole in the barrel assy. That's a real possible error I see but what do we have to verify that?

With all that said and for what I can tell without written specifications, there's an equal possibility that the bore alignment may become improved when all is said and done. Crazy I know! Mike says there's not going to be any significant movement. I'll take Mike's experience to the bank.

.015" is such a tiny space to work with here.

.015" is a LOT when you just took it off a piece of steel that didnt need it removed !

I can see a potential that if you accidently over cut the frame, the arbor could then become a fulcrum and the frame will lack sufficient tension with the arbor to ensure an all around solid union.

If there is room(clearance) around the arbour in its hole in the frame then the "too much off the frame" will maybe? tilt the barrel downwards as the wedge tightens and the clearance gap (if any is there) will be pie/wedge shaped but wider at the top rather than underneath side of the forcing cone - shorten the arbour button to get it square and you will have less cylinder gap - or none and bind the cylinder up - if the cylinder binds - what then? facing a few thou off the front of the cylinder would be no big deal - but we got kind of a chain reaction of compensating errors going on here !!! - its a darn good argument for going slow and careful at the start and thinking about what we doing - there is no place where "measure twice and cut once" is more appropriate than with this kind of work - putting metal back on gun parts where too much was took off from is real difficult.   

I believe that was also something Mike was alluding to as well. I feel sure you would want some tension at the frame as well. That said, I'm sure there's a point, if the gapping were so great, you would have no choice but to cut the frame or try a new barrel assembly. I only say these things out of intuition, not experience.

I came from the 1911 Forum where everything was about specification.

......

[greyhawk]

Greyhawk thanks and your assumption is correct about leaving the frame/bbl lug alone. In this instance though, the excessive clearance was created from a "too thick button" to begin with. The OP stated that it is a new revolver. The wedge can be  driven in enough to lockup the cylinder.  That being the case, you only need enough material (button, spacer, ) to hold the barrel at your desired spec.  Trying to "align" the frame/ bbl lug isn't the place to start.
  As far as barrel/frame alignment, adjusting for a .0025" - .003" (my spec.) or any of the others mentioned (don't know why anyone would want anything more than .004" but  .  .  .  what ever .  .  . ) is not going  be any significant movement. In any case, it will be the same form now on .  .  .  once sighted in, you're done.

Mike

Mike
thanks for the reply
yeah the couple of guns that I have messed with have been old replicas with some hard miles on them - impact wear on the recoil shields - and  waaaaaay too much clearance (even for Coffinmaker 
After this discussion would I still lop the frame joint dunno - it would depend how the gun looked without doing it and the clearance adjusted ..............

Hope all others here appreciate this bloke (Mike) does this as a business and still happy to lay it all out here for everybodys benefit - and do it in such a way we go away educated not chastised - thats very rare.....................

[45 Dragoon]

Thanks Greyhawk.  Most folks are curious by nature but I've found that knowing "what" and "how" doesn't necessarily translate to "do it myself".  It does let a customer know you sorta know how to fix theirs though!!   

Mike

[RUSS123]

Mike
thanks for the reply
yeah the couple of guns that I have messed with have been old replicas with some hard miles on them - impact wear on the recoil shields - and  waaaaaay too much clearance (even for Coffinmaker 
After this discussion would I still lop the frame joint dunno - it would depend how the gun looked without doing it and the clearance adjusted ..............

Hope all others here appreciate this bloke (Mike) does this as a business and still happy to lay it all out here for everybodys benefit - and do it in such a way we go away educated not chastised - thats very rare.....................

Rare indeed! Mike is the best thing that could have ever happen for the CAS community, without a doubt. I purchased my first Open Top this past Christmas and learned so much about them thanks to Mike, that, and how to make a great tasting burger! If and when I should purchase another OT model, it's going straight to Mike.

BYW, Mike, I bought the; "McCormick Grill Mates Montreal Steak Seasoning" to try out!