Nicksterdemus
Member
I have a mod 25-2 in 45 acp & thought about picking up a cylinder in 45 colt that may or may not have cut-out for full moon clip. First & foremost I wish to continue to be able to use the 45 acp cylinder that came w/frame at my discretion.
It's my understanding that B/C gap should be around 0.003-0.010 ever so roughly. Where is the point that's considered too much B/C gap?
What would be considered the maximum tolerance between a 45 colt, or loaded full moon clip of 45 acp, and the blast shield? I measured my 45 colt New Vaquero, but again I'm wondering how far one could/should go before being concerned w/piercing a primer.
Needless to say I've been shipped a well used cylinder that apparently has been modified by a less than proficient shade tree smitty. I would like to be able to avoid similar wares in the future.
Also on the yoke. Why would it slip on w/o the cylinder fine though bind upon coming close to closing unless bent?
I will be most appreciative of any tips or corrections to my limited assumptions.
ETA: What I've run into w/this cylinder is large B/C gap, the extractor fitting so tight against the recoil shield that I thought a shim could relieve, but also to much of a gap from the heel of the cartridge to the recoil shield.
I might be misusing the term recoil shield as I measured the cartridge in the top hole to the firing pin slot.
I have too much on both ends of the cylinder and it seemed that the star extractor was too tight. The tip of the extractor rod had been shaved a mite for a previous fit though I think that is of no issue.
ETA II: I'd think it quite common for functional used revolvers to run .015-.020 gap, yet where would you draw the line at good enough/too much?
The 1903 .32 I picked up from 1910, my evaluation over advertised 1906, is .010. My 38 spl 4th change SN 2554XX circa 1916 w/late 1946 S 9308XX brl filed on a slant, .003 or .005 depending on which side. I guess .004 splitting the dif will suffice. Mod 1917 11907X 45 acp is .009. Last though not least is the 1979 25-2 also in 45 acp coming in at .012. Seems if you desire a build as tight as a century ago you have to pay a premium through the Performance Center offerings.
I can load Blazer Al case 38 spl ammo and measure .0015/various other brass .001 from the back of the cartridge to the firing pin bushing on the old HE though I still don't know how wide is too wide on that end.
However, I would think over .025 might be a tad much.
Surely there's a somewhat standardized measurement. I suppose it's my fault for not wishing to discuss the ever popular end shake.
ETA III:
Maximum headspace is what I was looking for. Of course you already know that headspace/endshake/B/C gap are all interrelated. I found this, pertaining to SAA, whilst researching.
http://www.cascity.com/forumhall/index.php?topic=14265.0;wap2
'Headspace' with the SAA is not a hard number. It varies slightly by cartridge. In the case of the SAA, headspace is defined as the distance between the rear of the cylinder and the front of the recoil shield, not the clearance between the rear of the rim, and the recoil shield, as rim thickness can vary.
Here is what Kuhnahausen has to say on the subject:
Cartridge Case Rim Thickness Case Head Clearance Headspace Gauge Rim WIdth
45 Colt .049 min/.060 max .006 .062 (go) .067 (no go)
44-40 .055 min/.065 max .006 .067 (go) .072 (no go)
44 Special .049 min/.060 max .006 .062 (go) .067 (no go)
38-40 .055 min/.065 max .006 .067 (go) .072 (no go)
38 Special .048 min/.059 max .006 .060 (go) .066 (no go)
357 Magnum .049 min/.060 max .006 .060 (go) .067 (no go)
32-20 .055 min/.065max .006 .067 (go) .072 (no go)
Notice that in this chart, the headspace is a range, not a single dimension. This would be the numbers under the Headspace Gauge Rim Width column. The 'Case Head Clearance' number is just an average, it will depend on the actual rim thickness. So with a wost case 45 Colt rim thickness of .060, the smallest allowable head space of .062 will still allow .002 of clearance between the rim and the recoil shield. Whereas the thinnest rim, or .049 and the widest allowable headspace of .067 will allow .018 of clearance. As with all mechanical tolerances, there are usually other considerations too. Firing pin protrusion for the SAA is specified as .045 min and .056 max. If there is too much clearance between the rim of a cartridge and the recoil shield, it is conceivable that a firing pin may not protrude enough to reliably fire a cartridge.
It also needs to be stated that these numbers assume zero endshake. "Although headspace can be estimated with the cylinder pushed to the rear, accurate measurement requires that cylinder endplay be reduced to as close to zero as possible." Kuhnhausen
As well on this forum I found this:
"To measure the head space, measure it with a cartridge in the chamber. First measure the rim, then add feeler gauge then add both values up.
This is from S&W.......
I added the gage specifications below for each particular caliber (from the armorer's manual):
38,357,41,44 .060"-.068"
22 magnum .004"-.008"
45 ACP .090"-.094"
45 Long Colt .060"-.068"
38,357 w/cylinder Counter Bore .012"-.018""
It seems that the minimum case rim thickness, for the 45 Colt & some others, is .011 less than the maximum rim thickness. In this 45 Colt case of .060. This tells me that in a worst case scenario for maximum allowable headspace is .018 from the back of the thinnest cartridge to the recoil shield. If a .025 feeler gauge falls in the gap then I'll speculate that's at least .026 & .008 too much space SAA or .006 S&W.
Granted, if that width was relieved by .008 then that would add to the B'C gap. Which could be relieved by bringing the barrel in further. At the risk of my current cylinder's B/C gap not having that much room. I can't hardly see shaving the factory 45 acp cylinder, that's within specs, to accommodate a spare 45 colt that a wee bit light on the length.
As always I extend an invitation to correct any misconceptions I may have inadvertently latched upon.
It's my understanding that B/C gap should be around 0.003-0.010 ever so roughly. Where is the point that's considered too much B/C gap?
What would be considered the maximum tolerance between a 45 colt, or loaded full moon clip of 45 acp, and the blast shield? I measured my 45 colt New Vaquero, but again I'm wondering how far one could/should go before being concerned w/piercing a primer.
Needless to say I've been shipped a well used cylinder that apparently has been modified by a less than proficient shade tree smitty. I would like to be able to avoid similar wares in the future.
Also on the yoke. Why would it slip on w/o the cylinder fine though bind upon coming close to closing unless bent?
I will be most appreciative of any tips or corrections to my limited assumptions.
ETA: What I've run into w/this cylinder is large B/C gap, the extractor fitting so tight against the recoil shield that I thought a shim could relieve, but also to much of a gap from the heel of the cartridge to the recoil shield.
I might be misusing the term recoil shield as I measured the cartridge in the top hole to the firing pin slot.
I have too much on both ends of the cylinder and it seemed that the star extractor was too tight. The tip of the extractor rod had been shaved a mite for a previous fit though I think that is of no issue.
ETA II: I'd think it quite common for functional used revolvers to run .015-.020 gap, yet where would you draw the line at good enough/too much?
The 1903 .32 I picked up from 1910, my evaluation over advertised 1906, is .010. My 38 spl 4th change SN 2554XX circa 1916 w/late 1946 S 9308XX brl filed on a slant, .003 or .005 depending on which side. I guess .004 splitting the dif will suffice. Mod 1917 11907X 45 acp is .009. Last though not least is the 1979 25-2 also in 45 acp coming in at .012. Seems if you desire a build as tight as a century ago you have to pay a premium through the Performance Center offerings.
I can load Blazer Al case 38 spl ammo and measure .0015/various other brass .001 from the back of the cartridge to the firing pin bushing on the old HE though I still don't know how wide is too wide on that end.
However, I would think over .025 might be a tad much.
Surely there's a somewhat standardized measurement. I suppose it's my fault for not wishing to discuss the ever popular end shake.
ETA III:
Maximum headspace is what I was looking for. Of course you already know that headspace/endshake/B/C gap are all interrelated. I found this, pertaining to SAA, whilst researching.
http://www.cascity.com/forumhall/index.php?topic=14265.0;wap2
'Headspace' with the SAA is not a hard number. It varies slightly by cartridge. In the case of the SAA, headspace is defined as the distance between the rear of the cylinder and the front of the recoil shield, not the clearance between the rear of the rim, and the recoil shield, as rim thickness can vary.
Here is what Kuhnahausen has to say on the subject:
Cartridge Case Rim Thickness Case Head Clearance Headspace Gauge Rim WIdth
45 Colt .049 min/.060 max .006 .062 (go) .067 (no go)
44-40 .055 min/.065 max .006 .067 (go) .072 (no go)
44 Special .049 min/.060 max .006 .062 (go) .067 (no go)
38-40 .055 min/.065 max .006 .067 (go) .072 (no go)
38 Special .048 min/.059 max .006 .060 (go) .066 (no go)
357 Magnum .049 min/.060 max .006 .060 (go) .067 (no go)
32-20 .055 min/.065max .006 .067 (go) .072 (no go)
Notice that in this chart, the headspace is a range, not a single dimension. This would be the numbers under the Headspace Gauge Rim Width column. The 'Case Head Clearance' number is just an average, it will depend on the actual rim thickness. So with a wost case 45 Colt rim thickness of .060, the smallest allowable head space of .062 will still allow .002 of clearance between the rim and the recoil shield. Whereas the thinnest rim, or .049 and the widest allowable headspace of .067 will allow .018 of clearance. As with all mechanical tolerances, there are usually other considerations too. Firing pin protrusion for the SAA is specified as .045 min and .056 max. If there is too much clearance between the rim of a cartridge and the recoil shield, it is conceivable that a firing pin may not protrude enough to reliably fire a cartridge.
It also needs to be stated that these numbers assume zero endshake. "Although headspace can be estimated with the cylinder pushed to the rear, accurate measurement requires that cylinder endplay be reduced to as close to zero as possible." Kuhnhausen
As well on this forum I found this:
"To measure the head space, measure it with a cartridge in the chamber. First measure the rim, then add feeler gauge then add both values up.
This is from S&W.......
I added the gage specifications below for each particular caliber (from the armorer's manual):
38,357,41,44 .060"-.068"
22 magnum .004"-.008"
45 ACP .090"-.094"
45 Long Colt .060"-.068"
38,357 w/cylinder Counter Bore .012"-.018""
It seems that the minimum case rim thickness, for the 45 Colt & some others, is .011 less than the maximum rim thickness. In this 45 Colt case of .060. This tells me that in a worst case scenario for maximum allowable headspace is .018 from the back of the thinnest cartridge to the recoil shield. If a .025 feeler gauge falls in the gap then I'll speculate that's at least .026 & .008 too much space SAA or .006 S&W.
Granted, if that width was relieved by .008 then that would add to the B'C gap. Which could be relieved by bringing the barrel in further. At the risk of my current cylinder's B/C gap not having that much room. I can't hardly see shaving the factory 45 acp cylinder, that's within specs, to accommodate a spare 45 colt that a wee bit light on the length.
As always I extend an invitation to correct any misconceptions I may have inadvertently latched upon.
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