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Revolver cylinder location accuracy

penguin1penguin1 Member Posts: 146 ✭✭
edited June 2019 in Ask the Experts
I read of checking to see if one position of the cylinder is more accurate than others. Is this a common procedure?

Comments

  • nmyersnmyers Member Posts: 16,793 ✭✭✭✭
    edited November -1
    Never heard of that practice. Seems like you would have to paint or scribe a "position number" to each charging hole. With a high quality revolver, I would think that ammo variations would have a greater effect on accuracy than a small deviation in machining the parts of the gun.

    But, for safety purposes, I always check the alignment of each charging hole before buying a used revolver. I use a wood dowel. An alignment failure would shave lead, which would not only cause a flier but threaten the safety of the shooter on the firing point next to me. (I still have a tiny scar on my cheek from a friend's .22 revolver.)

    Neal
  • chris8X57chris8X57 Member Posts: 1,046 ✭✭✭
    edited November -1
    There are many factors that affect a revolvers cylinder timing- yoke alignment, fore and aft slop, cylinder stop side play, and other factors like ratchet pad wear depending on makes and models. Like for instance on a Smith and Wesson K frame, I have seen the ratchet pads filed more than others on the same cylinder, resulting in later timing of that particular cylinder hole. This is rare, but can happen with hand fitting. Also, a beat up cylinder stop notch can cause later timing. That is one reason all revolvers have a forcing cone cut into the breach end of the barrel- to allow for minute variations in alignment.

    Timing and alignment is checked with a precision range rod ( like the wooden rod but a better fit). There are other specialized tools- alignment mandrels for the yoke, frame rods to check alignment of barrel to firing pin hole, etc.

    Actual machining can be defined in what's called 'Positional Tolerancing'. In pre-CNC days, tooling to control hole locations in cylinders was made and tolerancing allowed a plus/minus deviation. Cutting a hole in six locations in true position is not difficult- even without a computer to figure your radial and x and y locations. I'm not sure what the big gun companies used, but when we bored a cylinder, we had a special lathe fixture that indexed off a master hole location, and each subsequent hole located off it.
  • pip5255pip5255 Member Posts: 1,614 ✭✭✭
    edited November -1
    I check my revolvers accuracy by using a paper saucer (like 5 or 6 inch) at 25 feet and if I can put them all on the saucer then my loads are good.
    just because you could doesn't mean you should
  • navc130navc130 Member Posts: 1,017 ✭✭✭
    edited June 2019
    When revolvers dominated Bullseye Target competition, it was discovered that one cylinder chamber may be more or less accurate than the others, either from alignment or chamber dimensions. This can be determined by shooting groups from each chamber in a machine rest. And no, it is not a common procedure. But, if one chamber is significantly less accurate than the others it is certainly worth knowing about. When testing a cylinder you have to mark/ID each chamber to record the results.
  • mrmike08075mrmike08075 Member Posts: 11,826 ✭✭✭
    edited November -1
    I was first made aware of the phenomenon through interaction with civil war reenactors...

    Later the concepts and underlying precepts were reinforced / confirmed by those in the cowboy action shooting field - SASS members...

    Apparently it was common to find Italian reproduction revolvers were the diameter of the cylinder chambers varied not only from gun to gun but on a single individual cylinder...

    Enough to noticeably impact accuracy and shot placement.

    I was introduced to the practice of measuring and recording the diameters of each cartridge acceptance chamber on an individual cylinder...

    The folk I was interacting with were having their cylinder chambers machined to closer tolerances - the end goal being each cartridge chamber on a cylinder having the same diameter - or having them as close to true / identical as possible...

    The practice has been referred to as blue printing or truing...

    Subsequently I had this modification performed on several of my own personal revolvers - and was pleased with the results...

    Again my introduction was via 1851 Colt Navy reproduction revolvers made in Italy but with further hands on investigation I discovered that the inside diameter variance issue was present on a wide range of revolvers (make - model - age - COO - etc...)

    I would humbly suggest that you randomly select revolvers from your own personal collection and perform a forensic investigation...

    In addition I think you will find that on any given cylinder you will have cartridge chambers that not only vary in dimension but that such variances indeed do impact accuracy and shot placement / group size...

    IMHO

    Mike
  • charliemeyer007charliemeyer007 Member Posts: 7,346 ✭✭✭
    edited November -1
    Some pistols shoot better than others. I have seen lead spitters that still shoot 'good'. Moving parts need room to move. If you have a quality pistol there more than a good chance it will shoot better than you can hold.
  • nononsensenononsense Member Posts: 10,934 ✭✭✭✭
    edited November -1
    penguin1,
    I read of checking to see if one position of the cylinder is more accurate than others. Is this a common procedure?

    The use of proper terminology is essential to understanding questions and providing answers. Hopefully you are asking about the alignment of the chambers with the barrel. If not, let me know and I'll delete this response.

    Alignment and fitting of parts in a revolver are critical to the function of the revolver but contribute very little to accuracy unless the condition is gross misalignment such as lead spitting, as pointed out above. Revolver gunsmiths go to great lengths to make certain that all the parts of a revolver ARE aligned and that the chambers are the correct size. But this can become problematic when we discuss a used firearms. Getting the revolver to function correctly is critical.

    However, accuracy of revolvers is based on a totally different idea. Here is an excerpt from Lt. Col. Douglas B. Wesson and his treatise 'Burning Powder':

    With the machine rest we have demonstrated by actual test the fact that with proper alignment of the barrel and cylinder of a revolver, the distance that the bullet has to jump after leaving the shell and before entering the barrel, has, within reasonable limits of jump, no effect whatsoever on the accuracy of the arm. This accounts for the fact that with our K-.22 revolver we can make at 30 feet most excellent machine rest groups using the tiny CB caps, and with .38 S&W Special Mid-Range Wad cutter ammunition in our .357 Magnum at 60 feet we will secure six-shot groups that can be more than covered with a dime.

    For those wishing to read the entire excerpt, here is the link:

    http://sportsmansvintagepress.com/read-free/burning-powder-table-contents/smith-wesson-revolver-accuracy/

    The complete book is also available for purchase at the end of the article.

    Best.
  • bearman49709bearman49709 Member Posts: 506 ✭✭✭
    edited November -1
    Not very common, but as navc130 wrote you mark each chamber then fire a group. Marking each chamber can be done with a marker placing from one to six dots, permanent numbers can be stamped by each chamber.
  • WarbirdsWarbirds Member Posts: 16,506 ✭✭✭✭
    edited November -1
    Thanks for sharing this!
    chris8X57 wrote:
    There are many factors that affect a revolvers cylinder timing- yoke alignment, fore and aft slop, cylinder stop side play, and other factors like ratchet pad wear depending on makes and models. Like for instance on a Smith and Wesson K frame, I have seen the ratchet pads filed more than others on the same cylinder, resulting in later timing of that particular cylinder hole. This is rare, but can happen with hand fitting. Also, a beat up cylinder stop notch can cause later timing. That is one reason all revolvers have a forcing cone cut into the breach end of the barrel- to allow for minute variations in alignment.

    Timing and alignment is checked with a precision range rod ( like the wooden rod but a better fit). There are other specialized tools- alignment mandrels for the yoke, frame rods to check alignment of barrel to firing pin hole, etc.

    Actual machining can be defined in what's called 'Positional Tolerancing'. In pre-CNC days, tooling to control hole locations in cylinders was made and tolerancing allowed a plus/minus deviation. Cutting a hole in six locations in true position is not difficult- even without a computer to figure your radial and x and y locations. I'm not sure what the big gun companies used, but when we bored a cylinder, we had a special lathe fixture that indexed off a master hole location, and each subsequent hole located off it.
  • Toolman286Toolman286 Member Posts: 2,260 ✭✭✭✭
    edited November -1
    An old friend had a revolver with a wooden dowel jammed in one chamber. He said that his groups always had 1 slight flyer. So he numbered the chambers & fired test groups. Sure enough, 1 chamber fired larger & more erratic groups than the other 5. Hence, the wooden plug.
This discussion has been closed.