Quote:
Originally Posted by HogBob
All the replies seem to indicate the headspace (flashgap) is consistent as the cylinder rotates through six rounds . My 686-1 varies from .008" to .006" as the cylinder rotates. Is this variation normal? Any info that might help explain this revolver's erratic accuracy would be appreciated.
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Welcome to the forum, HogBob.
You raised a pretty old thread here; next time feel free to start a new one when there's a question that can't be answered with a search.
Some terminology issues in play. "Headspace" is measured between the rear of the cylinder (on the upper right side) and the recoil plate.
What you and thread starter are talking about is barrel to cylinder space, or b-c gap. It's correctly measured by manually holding the cylinder as far back as it will go, and inserting feeler gauges between the barrel face (sometimes mistakenly called the "forcing cone" which is a part of the barrel face) and the held back cylinder. You can measure either from the left or right sides, but sometimes one side can be slightly tighter than the other (if, for instance, the barrel face isn't perfectly true), in which case measure from the more open side. Accurate measurement is when the feel slide snugly in but isn't forced.
Generally, barrel to cylinder gap is even through cylinder rotation, though it is very common to have mild variance. If you've measure gap correctly, .006" to .008" variation is mild and personally I wouldn't worry about it; both measurements are within old school factory specs.
Possible explanations include the cylinder face isn't perfectly square (cut flat and even), the yoke could be sprung (bent), or both at the same time.
Erratic accuracy can have various causes -- the two most common are user error, and either cheap or poorly reloaded ammo, with mechanical issues third. For mechaical explanations, indexing, or the proper aligning of the charge hole with the barrel face prior to ignition -- a function of correct timing -- can contribute to accuracy issues, but thtere are many other possibilities.
Are you spitting or shaving lead when firing? Any other abnormalities?
Best first thing to do to determine accuracy problems is get factory match loads, use a rest, shoot single action, and have an informed partner to observe and also shoot.
As for possible mechanical issues, best first step is have a qualified revolversmith perform a basic set of spec checks based on your experiences and concerns with the revolver. Finding a sprung yoke and the like is easy, quick fixing and inexpensive.
If the cylinder face is measurably untrue, I'd leave that be given that you don't report any binding issues; .002" variation is minor and it's a more involved machining fix.