Barrel/cylinder gap

[45 Dragoon]

Mizar, if I have a .003" gap (measured cyl forward) and a .005" measurement with cylinder pulled back, I have .002" of endshake. If I remove the endshake by shimming the bushing ( ie on my SAA copy) I end up a .005" gap with "0" endshake (numbers are just for easy math).

Mike

 

[Mizar]

Mike, that hypothetical .005" clearance is what you will get when shooting the revolver - you get the B/C gap at it's maximum dimension EVERY time when a cartridge is fired. Why I'm saying that B/C gap and endshake are not directly related - you can have the max gap to be in factory spec, but have excessive endshake and you can have max B/C gap out of spec, but endshake to be at the minimum. With the hammer at rest one sees a smaller gap, but this is purely cosmetic, of no concern at all. All of this is said because I want to explain clearly, that one will not widen the B/C gap when correcting excessive endshake, because that "excessive" gap is already there and working - you just don't see it when looking at the revolver...

 

[45 Dragoon]

Mizar, I understand where you're coming from as it's basically semantics and what you're saying is true. The important thing is being able decipher the amount of endshake so you can get rid of it. It's the endshake that is unwanted.
Just as those numbers concerning my ROA's, they cover the spectrum but all four of them are absolute tack drivers. If I had to pick the one that would last as a max extreme shooter "as is", I'd have to go with the one with "0" endshake.

( this is an edit. Actually (after looking back at my own ROA numbers) I'd choose the first one with .0035" endshake. That .0005" removed gives me a .0035 gap with "0" endshake)

Mike

 

[RainDodger]

... and that gap (which is technically called the "gauge") is what may be causing a problem for me. I bought a brand spankin' new King Cobra in May. On the first range trip it was binding up in double action, although I could overcome the binding by manually cocking the hammer. I measured the gap at a tight .0015". That is EXTREMELY tight, as you guys know. I called Colt and they said to send it back. Fast forward, the revolver comes back to me. For grins I measured the gap. It measured .002", which is ALSO extremely tight, but the gun felt outstanding. Took it to the range and it made it through 24 rounds before starting to bind up. I'm not sure the gap caused the problem, but the gun is back at Colt as I type this. That brings me to the point that... these guns are likely very tight in all aspects, as they're CNC machined, with less hands-on assembly and finishing. I would guess there's going to be teething problems when new models come out. Anyway, that's my story and I'm stickin' with it. I think the gaps the OP posted are just about right. A former Colt gunsmith (from the 90s) told me that Colt cylinder gaps should be on the order of .004"-.006", but that was with older guns, so I don't know how it translates to today's precision.

 

[4v50 Gary]

Every mfg had a difference tolerance. Dunno what they were though. It's been decades since I've serviced a revolver.

 

[Kookla]

Learned true happiness with a revolver when I put away the gap gauges.

 

[mcb]

Learned true happiness with a revolver when I put away the gap gauges.

Amen!

Some of my revolvers are old and well used and have some fairly large cylinder gaps but the timing is good and they still shoot straight so I don't freight it much and just have fun shooting them.

 

[Vern Humphrey]

Do you guys measure barrel gap with the cylinder pushed forward as far as possible or back as far a possible?

The true barrel gap is whatever it is when the bullet emerges from the chamber. Since recoil starts when the bullet begins to move, the cylinder is fully back when the bullet emerges, so measure barrel gap with the cylinder fully back.

 

[unspellable]

Using a Dan Wesson 44 Mag with user adjustable cylinder gap I did some experimenting. At 0.012 the revolver started spitting crap back at me. I regard 0.008 as the maximum, S&W's 0.010 spec is too much. Changing the gap in the 0.002 to 0.008 made less difference in velocity than I expected.