Resetting S&W(N-frame)cylinder gap?


December 1, 2004, 03:38 PM
I have a late model(1984)S&W M28-3(Highway Patrolman). This gun has not been fired much at all. The cylinder to barrel gap, measures .007". Is this gap OK-or, if too excessive, what is the proceedure that I could follow(If possible?)to shim the cylinder to obtain a cylinder gap of .004" to .006"? Is there any problems with doing this(Either in doing the job itself-or, in the end result of doing this?)? Or, since this gun hasn't been fired much, should I leave this cylinder/barrel gap(.007")just as it is? I can't imagine, that this gun has been shot loose(Since it has hardly been fired at all?)so, it would seem, that S&W just built this M28-3 with this looser, barrel/cylinder gap? Please fully explain and clarify your answers? Thanks.

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December 1, 2004, 05:05 PM
Hello, reducing barrel gap is done by removing the barrel and adding a few threads to screw it in further. Recuting the forcing cone end regaps it.
I wouldn't worry much about .007, S&W allows up to .010 and calls it in spec!

December 1, 2004, 05:37 PM
S&W has changed the cylinder gap specs.It used to be IIRC .002-.006 , now it's 002-010". I wouldn't worry about .007"

December 1, 2004, 06:18 PM
7 thou is a good place to be, not loose enough to cause any problems at all yet loose enough to guarantee reliability. I think 5 is perfect, 7 is PLENTY good. My advise is to shoot it until it gets some endshake, then send it in for repair and have them set the gap to 5 thou.

I own Smiths with gaps from .002" to .014". The tight ones will bind as the cylinder and forcing cone gather lead and fouling, the loose ones blow fire, but they all work OK at least for a while.

December 1, 2004, 06:28 PM
I thought that there was a proceedure to somehow use shims to tighten up the cylinder/barrel gap? Is this much of a problem to do? Or, still not worth the trouble? If this could easily be done, where can the proper shims be obtained? Thanks.

December 1, 2004, 06:41 PM
Nope, the shim kits available from Brownells are for adjusting end shake as mentioned above..Not Barrel Gap.

Old Fuff
December 1, 2004, 07:19 PM
"Endshake" is back & forth movement of the cylinder (as opposed to rotational movement when the cylinder is locked). The shims (called "endshake bearings") refered to will correct endshake, but they increase cylinder-barrel gap - not decrease it - because they move the cylinder backwards.

If a revolver has an excessive gap that is causing problems such as lead spitting the proper correction is to first correct any excessive endshake and then remove the barrel, set the shoulder forward, and then screw it back into the frame. If necessary, this might be best done at the manufacturer's factory.

At the present time I doubt that your .007" gap is too much, and may be good if you shoot lead bullets. Tight gaps work when jacketed bullets are shot exclusively and may result in slightly higher velocities. I prefer to have my cylinder gaps adjusted so that I can use any kind of bullets, and usually use lead rather then jacketed. Among other advantages you will get longer barrel life.

December 1, 2004, 11:53 PM
1)I don't plan to shoot metal jacketed bullets. The only jackeded bullets, that I have to shoot(Until they are gone!)are some Federal Nyclad 38 +P ammo!

2)Otherwise, I'll just be shooting lead bullets(Mostly, .38 Special caliber)!

3)Old Fuff: I'm sure glad, that you think that my cylinder/barrel gap, will be OK, at .007"-as I was not looking forward to needing my M28-3 to have to be worked on, to tighten-up this gap-as this worried me-because the gun has not been fired very much(Only enough to put a lightly polished cylinder ring on the cylinder-but, not cut into the metal!)and with no burn marks or any bluing, scrubbed off the front of the cylinder!

Dave Sample
December 2, 2004, 12:39 AM
Double 007 has a nice ring to it for lead bullets as they tend to mess up the front of the cylinder. An 11 degree forcing cone and a facing reamer sometimes helps that, but in this case I would leave it like it is.

December 2, 2004, 01:56 AM
Dave Sample:

Thanks, I'm feeling better already, about that .007 cylinder/barrel gap! For awhile, I was wondering if I just had a poorly built, M28-3? Not a good thought, since I had just purchased this gun!

Dave Sample
December 5, 2004, 04:57 PM
"All revolvers:0.004-0.010. Note: If the ammunition being used tends to cause a buildup on the butt end of the barrel, it may be necessary to change ammuntion or increase the front gage."
That is what the book says about the cylinder gap. Your's appears to be just right according to them for lead bullets. Hope this helps.

December 6, 2004, 01:17 PM

Thank you, very much! I appreciate your informative input! Maybe I don't have a "Dog" of an M28-3(That I first thought-in view of the "Seemingly" wide, .007" cylinder/barrel gap!)? Except for just a light to medium, cylinder ring, my M28-3 looks to be in like new condition?

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