Posted: 4/30/2009 12:33:59 PM EDT
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I've read that a proper cylinder gap is around .003" - .004". Measuring this gap on my 4 S&W revolvers I get:
M18 (22lr/K frame) - .0015" (or less) M63 (22lr/J frame) - .0015" M442 (38 special/J frame) - .007" Perf Center M27 - .007" Measured with an automotive feeler gauge with the hammer lowered and the trigger held down. Aren't the 22 lr models a bit tight? I do get binding after just a few rounds on the M18 and after a few more rounds on the M63. The M442 is a new gun and might just be crappy. The S&W tuned performance center gun surprises me though. Of course given that it's the most accurate centerfire handgun I or any of my friends have ever fired and I'm not concerned about a little loss in velocity, it's OK. So, any thoughts on why the numbers are all over the place? How does one increase the gap on the M63/M18? How big of a downside is the extra gap in the 442? I realize I lose some velocity but how much are we talking about? Or am I just not getting the whole cylinder gap thing and I need additional information? |
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Probably the ideal barrel/cylinder gap is about 0.005".
Tighter and you may start to have binding problems from fouling build up or heat expansion. Too much over that is considered to be not good, with something around 0.008" to 0.009" being about the max want to see. They seemed to hold the .22's tighter so they typically have tighter gaps. Problem is, S&W has been loosening the specs over the last 30 to 40 years. Years ago, 0.009" was out of spec. Today, S&W is telling customers that gaps of as much as 0.012" in a center fire model is "in spec". The fluctuation seems to be more to the looser side than the tighter side, but does vary. Also, holding the trigger back is NOT the proper way to measure barrel/cylinder gap. The only thing measured with the trigger back is cylinder lock up on the old COLT double action revolvers. This is done to check whether the old Colt "Bank Vault" lockup is actually locking the cylinder tightly at ignition. Holding the trigger back on any other gun, including the S&W is not correct, and may give you false measurements. To measure barrel/cylinder gap on ANY brand of revolver, do it with the action at rest. |
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Quoted:
Probably the ideal barrel/cylinder gap is about 0.005". Tighter and you may start to have binding problems from fouling build up or heat expansion. Too much over that is considered to be not good, with something around 0.008" to 0.009" being about the max want to see. They seemed to hold the .22's tighter so they typically have tighter gaps. Problem is, S&W has been loosening the specs over the last 30 to 40 years. Years ago, 0.009" was out of spec. Today, S&W is telling customers that gaps of as much as 0.012" in a center fire model is "in spec". The fluctuation seems to be more to the looser side than the tighter side, but does vary. Also, holding the trigger back is NOT the proper way to measure barrel/cylinder gap. The only thing measured with the trigger back is cylinder lock up on the old COLT double action revolvers. This is done to check whether the old Colt "Bank Vault" lockup is actually locking the cylinder tightly at ignition. Holding the trigger back on any other gun, including the S&W is not correct, and may give you false measurements. To measure barrel/cylinder gap on ANY brand of revolver, do it with the action at rest. Measuring at rest is certainly is easier. Looks like the answer on my M18 is going to be keeping the cylinder face clean. Appreciate you taking the time to help bring others up to speed. |
| Dan Wesson supplied a .0015 guage for barrel instalation with their revolvers. Jim Clark supplied .0015 guage with Grand Master conversion PPC revolver. All my Smiths were within that range by + or - .0001. IF you shoot only jacketed bullets you could probably get away with tighter gap. With lead semi or full wadcutter type bullets you need the space for lead buildup. Timing the cylinder would be more important so as not to shave bullets. |
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Quoted:
Dan Wesson supplied a .0015 guage for barrel instalation with their revolvers. Jim Clark supplied .0015 guage with Grand Master conversion PPC revolver. All my Smiths were within that range by + or - .0001. IF you shoot only jacketed bullets you could probably get away with tighter gap. With lead semi or full wadcutter type bullets you need the space for lead buildup. Timing the cylinder would be more important so as not to shave bullets. Just out of curiosity, how are you holding barrel/cylinder gap within .0001"? I have always thought that ideal endshake should be around .001", so your barrel cylinder gap will at least vary by that amount. In fact, how are you even measuring the gap to the nearest ten thousandth? |
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One night a long time ago when I was tired, I read the end shake allowance on a Colt was very much less than on a Smith.
No, I don't understand the difference in the lockwork, but much above ~0.003" or so on a colt meant a lot of stuff would wear or loosen at a faster and faster rate and be expensive to fix. A similar end shake on a Smith was perfectly fine. I would have each Kuhnhausen book if they were not so expensive. |