Arbors and barrels and frames, oh my!

[Dave Shooter]

I've been trying to get smarter on how open tops fit.  Lots of good information here and on other sites.  One thing I didn't find was pictures to explain the relationships (maybe I just didn't look hard enough).  So I selfishly created these to ask the knowledgeable folks out there if I'm on track to figuring this out.

Opinions encouraged!

Our ideal fit:

If the gap is too wide we can slightly shorten arbor so long as contact is maintained with barrel.  If more gap reduction is needed we'd shorten both arbor and barrel at locator pins (or shorten frame if you can remove pins or work around them).


Often though we get a short arbor:



Problems can arise:



Another scenario can arise where arbor and barrel are in contact, but the barrel will contact the cylinder before it contacts the frame at the locator pins:

I actually have this with one of my Ubertis.  The arbor was too short and in the process of fitting the extension the arbor bottoms out, but the cylinder gap is ~.001" while a .006 feeler gauge fits between barrel and frame at locator pins.  It doesn't bind, at least not in a clean and oiled state; I haven't shot it like this.
I figure the hobbyist (one who lacks welding skills) has two principle options.
-a) shoot it as is
-b) shorten arbor to get contact at locator pins AND face off the rear of barrel at the forcing cone to set cylinder gap

I didn't really address wedge fit here.  Maybe someone can produce a part 2?

[ssb73q]

Hi Dave, nice write up! You understand the issues well.

Option b seems to be the way to resolve drawing 4.

BTW, I have found that a barrel/cylinder gap less than 0.003" can be problematic with black powder.

Regards,
Richard

[Captainkirk]

Seems like you pretty much nailed it, Dave. Nice schematics.

[mike116]

You have a good grasp of the concept Dave.  You have also succeeded in illustrating it in a easy to understand format.   Maybe we should sticky those drawings in the Knowledge Vault and refer others to it when the subject arises again.

[45 Dragoon]

Hey Dave, I agree, nice diagrams of the problems facing open top revolvers from Italy.

Of course, Richard is going to disagree with what I have, for years now,  posted as a barrel/cylinder clearance of .0025"-.003" as my standard. Don't know why that is but, guess I'll learn how to do what I do correctly one of these days. One minute I'm being asked to rewrite the "Bible" sarcastically (by you know who, different post) , then, apparently, I'm schooled on barrel/cyl clearances. 

 Oh well, take your pick but I haven't had anyone have problems with my clearances. On the contrary, more like, "how many more shots I can take without any binding " are the norm.  The maximum, I think, should be .003".  I'm sure that's not the correct setup but it's worked for my customers and my own revolvers (cartridge converted, smokless shooters) have a clearance of .0015"! Amazingly, they work EXTREMELY well that way so,  .  .  .  .  . I think I'll keep them that way!! Lol!!

For what it's worth, don't try a frame mounted coil and pushrod hand spring conversion or a torsion spring bolt or trigger spring, they work exceedingly well!! Not to mention, a coil setup can be done on a Remington as well which gives it "Ruger life span"/ durability (just a waste)!! Bolt blocks? Forget about um!! Action stops? No need ! Actually, bone stock is the way to go. Factory perfect is .  .  .  . perfection!! 

Mike
www.goonsgunworks.com
Follow me on Instagram @ goonsgunworks

[ssb73q]

Hi Mike, I never take the bible literately. I think you should write articles on BP revolver optimization. I take the Pettifogger articles as a guide. IMO technology can always be improved.

Back to the specifics of barrel gap on a black powder revolver. I shoot black powder and BP subs, I shoot a lot at my private range. When I have barrel gaps less than 0.003", fouling at the cylinder face barrel end becomes a problem. The narrow gap BP revolver may run for a cylinder or two, but shoot it a lot and fouling will stop it and definitely cause cylinder drag. My converted BP revolvers that use smokeless powder will run well a narrow gap.

You said that you rarely shoot BP, but mostly smokeless conversions. Maybe you need to get the BP revolver back out with narrow gaps where you shoot the revolver a lot?

BTW, you seem to always take my comments personal. Don't. A pissing contest serves nobody.

Regards,
Richard

[45 Dragoon]

Richard, pretty much all my customers shoot b.p.  Many of them shoot CAS matches and they shoot the whole match without binding. In fact, many can shoot into the 100+ rounds without binding, without taking the barrel off, without cap jams. There is also the comment about how much cleaner the revolver is at the end of a shooting session. I think I'll keep doing what I'm doing.
 The proof doesn't matter if I shoot b.p. or not or even shoot  at all.
  Folks that drive race cars don't build chassis's, don't build engines, .  .  .   everybody does what they do best. I like making cap guns faster than their shooters.

As far as barrel/cyl clearance, I doubt there is but a few folks here and on other forums that don't know I set these clearances close, with .003" being the max that I allow. Even says so on my website .  .  .  .  so, excuse me for thinking you were goading me "slightly".  And no pissing contest for me, I'm too busy figuring out better setups that make cap guns run better, faster, longer and too many happy customers to get pissy. Don't have that kinda time!!

Mike
www.goonsgunworks.com
Follow me on Instagram @goonsgunworks

[45 Dragoon]

Dave,
  In your last diagram, the arbor is taking over the "fulcrum" or pivot point and now has an impossible job of defining a bbl/cyl clearance without support from the frame (the true pivot pt.). I wouldn't shoot it in this condition. Of course the best solution is to reduce the arbor to regain contact at the frame/bbl lug and it should be contact under tension which is very important. Then face the barrel for clearance with the cyl.
  This will probably enlarge the wedge slot to the point that your wedge will bottom out.  You'll probably have to make a wider wedge or add a shim or have someone Weld some material to your wedge. This is what happens when you reduce the length of the arbor, you open the slot which requires more wedge which is why I install a 1/4" set screw (faced and polished) as a bearing surface for the wedge. That way, your wedge will always work and gives you the ability to "customize" your wedge placement or depth in the wedge slot.

Mike
www.goonsgunworks.com
Follow me on Instagram @goonsgunworks

[Dave Shooter]

I got a Brownells chamfering kit and 90° facing cutter the other day.  Been wanting one for some time for a couple projects.  Snow day so got to break it in on this '60 barrel.

Realized I ordered the .45 cal pilot and it won't fit in a .44 C&B bore.     What to do?  Order the .44 pilot and wait?  I'm impatient--bubba something together!  The pilots are brass, and the drive is basically 1/4" rod threaded on one end with a flat milled on the other to secure handle.  Hmmmm, brass, what could fit in bore but snug, .40 S&W case fits just a little loose, 10mm case more bearing surface and large primer pocket so less material to drill out to 1/4".  A single layer of tape got it snug in the bore, and voila, I have a pilot!



Inserted in bore with rod through it.  Cutter threads onto end.


Brownells cutter gives a very nice, smooth cut.


So, the arbor length is adjusted and barrel faced.  No binding and less than .002" clearance.  We'll see how it shoots; can always take more off if fouling really is problem.

[45 Dragoon]

Looks great Dave!! Is the  bbl /cyl  parallel now?

Mike
www.goonsgunworks.com
Follow me on Instagram @ goonsgunworks

[Dave Shooter]

Mike, very close.  Although, as you warned,the wedge is bottoming out; not loose per se, but no more room to tighten.  So may cut off my button, bed it in bottom of arbor hole, and use hole drilled in arbor for set screw.

[45 Dragoon]

Very wise move!
Use your button head as a shim and afix it to the bottom of the arbor hole. You should end up with the same setup, just better "placed"! Lol !!

Mike
www.goonsgunworks.com
Follow me on Instagram @ goonsgunworks

[ssb73q]

Hi Dave, that rear barrel end looks great!! Nice work.

Regards,
Richard