Enfield revolver no2 mk1 cylinder gap specs
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Thread: Enfield revolver no2 mk1 cylinder gap specs

  1. #1
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    Default Enfield revolver no2 mk1 cylinder gap specs

    Here's a question for the British Commonwealth gun plumbers. Picked up a pretty nice looking No.2 Mk1* that appears to have been on a shelf since its last FTR in 1954. Alas, loading it up, there is insufficient clearance; the cylinder virtually locks up trying to fire. In researching around the internet I came across this tidbit.

    Rear 0.07" must pass across striker hole
    Front, with cylinder held forwards. Must be between .002" and .018" on each chamber

    FPP, ,040" and .050"


    This particular revolver at the rear will pass a snug .049 across the firing pin hole. The gap with the cylinder forward is between .018 and .022. After removing the cylinder, there is a shim on the cylinder spindle that were it about .010 thinner would close up the cylinder gap and increase the headspace to where the cartridges won't drag.

    The shim, or whatever it is properly called, does not appear in any parts diagram I have found. What I would like to know is did the REME have an assortment of these shims to pick from to get the clearances correct? If so, where to find such an assortment now.

    I suppose that I could just lap the shim presently installed until enough clearance was achieved to allow the loaded cylinder to turn acceptably, but will cylinder moving forward affect the timing enough to worry about? As long as the cylinder stop is firmly engaged at the time of firing seems to me should be safe enough.

    Looking for advice on the best way to proceed. I have loaded a bunch of 200 grain lead bullets to duplicate .380/200 Revolver Mk I and I want to shoot it.

  2. #2

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    I'm pretty sure the shim was someone else's idea, not Enfield's. Also, the reason for the shim is that your revolver has excessive wear. I have an old Webley No. 2 Mk IV with the same problem. I used a shim to repair it.

    I have made these shims myself. I buy cheap feeler gauge sets and use them as the basis for shims. Your shim is way too thick. My best results have always been obtained by using whatever size shims give me between a .004" and .006" barrel/cylinder gap.

    PowerCustom makes end shake bearings/shims for S&W revolvers that will sometimes work as-is, and sometimes you have to reduce the outside diameter a bit. As far as I know they only come in two thicknesses, .002" and .004". The O.D. is .375" and the I.D. is .250". Not cheap but probably worth a shot. Brownell's carries them:
    http://www.brownells.com/rifle-parts...-prod9858.aspx

    So... you can make a shim from a donor feeler gauge or try the PowerCustom bearings. You are looking at a .010" thickness, but I think that leaves your barrel/cylinder gap too large at .008" to .012". My preference would be more on the order of a .004" shim. Your gun, your call, but I agree that as long as the cylinder stop is engaged I think you are safe to shoot the gun.
    Last edited by VeloDog455; 04-18-2017 at 09:04 AM.

  3. #3
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    The more I look at this old revolver, the more I wonder bout it. The finish looks like typical military phosphate, and there are no import marks. It appears not to have been fired since the refinish, which if it coincides with the FTR, was 60 years ago. So when fitting and repairing these revolvers, how did the Brits ensure the cylinder was properly positioned to have the correct clearances? Was it all supposed to be controlled by the Cylinder Retaining Cam?

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  5. #4
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    The correct gap between the rear of the cylinder and the frame of the Enfield revolver No2 Mk1 is less than .067 inch as determined by British armourer slip gauge SM148 which must not pass through the gap.
    The .018 to .002 inch for cylinder to barrel gap is a US specification for Smith & Wesson .38 caliber revolvers. I have not found a purpose built British gauge to check the gap. I suspect that a book of leaf gauges were used by British armourers and that the actual figurers are very close to or identical to the S&W figures.
    British armourers used gauge SM146 Hammer Point Protrusion for Enfield Revolver No2 Mk1, to determine if firing pin protrusion was within specifications of .04 to .05 inch.

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    The "Instructions for Armourers" supplement specifies the 0.067" maximum gauge "across each cylinder" and then goes on to say "at the same time see that the linear movement of the cylinder is not excessive and that the front end is clear of the barrel". No gap figure is mentioned.

    Peter

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    Quote Originally Posted by PJGP View Post
    The "Instructions for Armourers" supplement specifies the 0.067" maximum gauge "across each cylinder" and then goes on to say "at the same time see that the linear movement of the cylinder is not excessive and that the front end is clear of the barrel". No gap figure is mentioned.

    Peter
    Given that currently the headspace is insufficient with the shim in place and the cylinder barrel gap in non existent with the shim removed the solution would seem to be to lap the shim until a clearance of .060" is obtained at the breech end of the cylinder. The specified rim thickness for .38 S&W brass is .055 according to SAAMI so .003 to .005 from the case head to the recoil plate should be tolerable. With the shim in place now the gap between the cylinder and the barrel is between .018 and .022 inches so reducing that by .011-012 should cause no problems s long as the pawl still advances the cylinder enough for the stop to engage and lock it in position correctly.


  8. #7
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    Quote Originally Posted by PJGP View Post
    The "Instructions for Armourers" supplement specifies the 0.067" maximum gauge "across each cylinder" and then goes on to say "at the same time see that the linear movement of the cylinder is not excessive and that the front end is clear of the barrel". No gap figure is mentioned.

    Peter
    Given that currently the headspace is insufficient with the shim in place and the cylinder barrel gap in non existent with the shim removed the solution would seem to be to lap the shim until a clearance of .060" is obtained at the breech end of the cylinder. The specified rim thickness for .38 S&W brass is .055 according to SAAMI so .003 to .005 from the case head to the recoil plate should be tolerable. With the shim in place now the gap between the cylinder and the barrel is between .018 and .022 inches so reducing that by .011-012 should cause no problems s long as the pawl still advances the cylinder enough for the stop to engage and lock it in position correctly.


  9. #8
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    Removed the shim, reassembled the revolver and test fired it after work today. Three cylinders full, no malfunctions. Cursed mightily whoever installed the shim, all his ancestors and all their progeny. The results at 25 yards. Good enough for government work.

    Click image for larger version. 

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  10. #9

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    OK, but you still need to check it for end shake. Unload the gun. Pull the hammer back and pull the trigger all the way to the rear. Slowly ease the hammer down and, while maintaining rearward pressure on the trigger, pull the cylinder as far as it will go in the forward direction. While holding the cylinder forward, hold the gun up to a strong light to make sure you still have a barrel-cylinder gap. If you do see a gap you can also check it with a feeler gauge to see how much gap you actually have.

    If you can see that the barrel is touching the forcing cone then it will fire for a few rounds but eventually the carbon build up will make the trigger pull waaaay too hard. Your 18 rounds are probably too few to observe this phenomena.

    The more wear on the gun, the quicker this will happen but I find this usually occurs before you can get through a box of 50 rounds. Also, if the barrel IS touching the forcing cone you will want to consider a thinner shim than the one you removed, but you WILL need to shim it in order for it to work properly. Just my $.02.

    Here's hoping you don't have any end-shake, but it's hard to imagine why someone would go to the trouble of installing a shim they didn't need.

  11. #10
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    Quote Originally Posted by VeloDog455 View Post
    ... it's hard to imagine why someone would go to the trouble of installing a shim they didn't need.
    It is harder to understand why they would go to the trouble to make a shim that reduced the headspace to the point that cylinder would NOT turn when loaded. It was not an off the shelf shim from Brownell's or Power Custom as the diameters involved are not any sizes they stock. Additionally, this shim is nearly .032 thick, most all the standard cylinder or yoke bearings listed are just a few thousandths thick. Somebody went to a lot of work to screw up this revolver...then they sold it.
    Attached Thumbnails Attached Thumbnails 004.jpg   010.jpg   009.jpg  
    Last edited by old tanker; 04-20-2017 at 10:57 AM.

  12. #11
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    Quote Originally Posted by VeloDog455 View Post

    Here's hoping you don't have any end-shake, but it's hard to imagine why someone would go to the trouble of installing a shim they didn't need.
    My first guess would be that some previous owner obtained an off-the-shelf, oversized, shim, but never got around to cutting it down to where it would work.

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