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Discussion Starter · #1 ·
Hello all,

I have a SP101 that has an endshake issue. The origins of this come from a very high round count, mostly 158 grain 357's. The b/c gap runs between 0.0015 and 0.007. The trigger, timing, and everything on this gun is fantastic, with the exception of an endshake of 0.0055. I found endshake shims to the order of 0.004 and am interested in installing them but am concerned about truing the inside surface of the cylinder, the yoke tube appears peened from visual inspection and I expect the mating surface of the cylinder to be similar. Now I know about the special tool to take the cylinder apart and currently the only shims available are 0.004, which is perfect for my needs. I would love to send it to ruger but the gun is fantastic as it sits right now, it also has a spurred hammer that I replaced myself, trading off the DAO that it came with, and I am not willing to have it removed in order to be "factory fresh" as I have heard is often the case with warranty issues, if the warranty even still applies.

My question is how do I true the inner cylinder? And is it worth doing or should I wait until it opens up even further? The under the table "specs" call for 0.005 max, and I am just over the edge. This is my EDC and I am hesitant to use shims in any critical pressure point to begin with. If left in its current state my plan is to stick to 38's and only chalk up the mags for carry, hopefully reducing the issue entirely. Thoughts?
 

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I'd call up Ruger and see if they can return it back to new condition. They might surprise you.
 

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As you may already know a bushing will need to be installed in the front of your SP101’s cylinder in order to correct the end shake. This can be done by a competent gunsmith or at the factory, most of the time this is an opportunity to give the revolver a comprehensive tune up. With such a tune up springs are replaced and all other lock work closely inspected. I’ve had such work done at the factories on an S&W and Colt revolver which were purchased used and in poor condition. I would not hesitate to do the same again for a revolver I had owned and used for many years.
 

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Endshake is fore and aft cylinder movement when the cylinder is locked into the frame. The way to measure it is to use an automotive type gap gauge (feeler gauge) and measure the barrel-to-cylinder gap (B/C gap) by first wedging the cylinder fully forward. Measure the B/C gap again with the cylinder wedged fully to the rear. Endshake will be the difference between the two measurements. For a SP-101, you want about .002" but not more than .005". If endshake is too tight, the cylinder will bind up. If it is excessive, several conditions could result including misfires from light primer hits, cylinder unlatching when fired (very dangerous), cylinder dragging on the barrel, etc.

Endshake comes from four sources ... the end of the crane tube (S&W calls it a yoke tube) will peen and get shorter. A channel will get cut inside the cylinder's center hole, which is the mating surface for the crane tube. This causes the crane tube to seat deeper. The other two areas are the end of the ratchet column and the recoil shield where the ratchet column mates. Generally, all four surfaces will peen and increase endshake. Short of replacing the frame and/or cylinder, there's nothing you can do about excessive endshake if if comes from the recoil shield or the ratchet column.

How can you determine the source of the problem? If the cylinder moves too far rearward where the B/C gap exceeds .008" (.004"~.008 is normal, .006" is optimum), either the ratchet column has peened shorter or there is a depression in the recoil shield. You can usually see or feel a depression in the recoil shield. If the ratchet column is peened, the normally sharp edges will show evidence when compared to a new gun.

Based on the measurements posted by KaTo, it appears the B/C gap is wider than normal, which indicates a couple thousandths peening at the rear ... ratchet column, recoil shield, or both. The only fix is to replace the cylinder and/or frame but because the B/C gap is still in spec (barely) repair would not be necessary.

The worst issue is when the B/C gap is way too tight with the cylinder pushed forward ... almost causing the cylinder to scrape on the barrel. This can be repaired by installing "endshake bearings", which are nothing more than very thin washers. Before installing endshake bearings, two very important issues must be resolved. The first requires a "facing cutter" tool that removes a few thousandths from the end of the crane tube, removes the peened area, and squares up the end of the tube so it will mate properly with the bearing surface inside the cylinder's center hole. The inner hole mating surface must be dressed smooth and straight to eliminate the channel that was cut by the crane tube. The tool used to do this is a cylinder shaped grinder bit. I buy the ones with a 1/4" shaft and a 1/2" abrasive cylinder then use a shaping stone to size the diameter so it will just fit in the gun's cylinder center hole. After shaping the outside diameter, I use epoxy on the circumference of the body of the grinder bit so it won't damage or enlarge the diameter of the cylinder's center hole. This leaves a flat abrasive tip on the grinder bit so you can chuck the bit in a variable speed drill and hone the inside mating surface, typically removing about .005".

With the crane tube cut shorter and the inside cylinder hole deeper, it will increase endshake by several thousandths. No problem ... just stack endshake bearings until endshake measurements are within spec ... closer to .002" is best. Brownell's sells endshake bearings (made by Power Custom) in .002" thickness ... pack of 10 for about $20.

After endshake bearing are installed properly and endshake is well in spec, the gun will actually hold up better than when brand new. As noted above ... 357 Mag ammo takes its toll so it's much wiser to shoot 38 Specials for practice and run a cylinder or two of Mags now and then just for grins. If endshake is allowed to get out of control (more than .005"), it will allow enough fore and aft motion to "jackhammer" endshake much faster. At some point, the cylinder latch will release when fired and could result in a dangerous situation.
 

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Discussion Starter · #6 ·
Thanks Iowegan, I see how a tool of that fashion would do the job quite nicely. The epoxy shield is a great tip. I was also reminded that the ruger "warranty" is more of a handshake than a contract, I may have to touch base and see what develops. Either way I bet there are still quite a few rounds left in this ol' beastie.

Is there any worry about endshake bearing lifespan? I've found the end of the regular parts and am hoping for a longer-term solution. I might have to give single action a whirl in the near future. Ha, like I really needed an excuse!
 

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I have a SP101 that has an endshake issue. The origins of this come from a very high round count, mostly 158 grain 357's.
For all of the SP101 shooters convinced that the gun is indestructible, I was never inclined to believe it was true. But I'm also pretty sure it's fairly sturdy.

How many rounds of full power stuff does it take to shoot one loose?

My own SP101 gets a diet of cast 160gr SWC/6gr of Unique, or 158gr Jacketed 9gr of Blue Dot. Both moderate loads that should keep it healthy as long as I have left in this world. The difference in pressure, quite a bit, terminal performance, very little. The advantage of filling my own.
 

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Discussion Starter · #8 ·
Well I lost count but I believe it is easily sitting somewhere around the 2k+ mark, when I was buying new factory loaded ammo the price difference between a 357 and 38 was nominal. I shot a wide variety of ammo but my two favorites are the cci blazer hp, lightest magnum round, through the federal 158 sjsp, which is the hottest round of all those I have tried. I want to note that I never measured endshake when I originally purchased the ruger and have no benchmark from where it started. The end shake issue was discovered when I originally noticed cylinder drag as I recently switched to 38 special lead rounds at a now substantially lower cost, darn inflation at work. At the moment my plan is to get a new sp101 as my edc and promote my "well worn" sp101 to range and backup duty after repair is complete. Unfortunately I recently saw that my lg303 crimson grips might not fit the new 4.2" and there is a wrench tossed firmly into the works.
 

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TMan51, It's not possible to predict how many rounds it will take to shoot any revolver loose. So much depends on how the revolver left the factory and what type of ammo was fired in the gun. Assuming a SP-101 was shipped with near-zero endshake (normal, but not always) the first 100 rounds will peen the machine marks in all four of the areas mentioned in my above post. You can pretty much take it to the bank that endshake will increase about .002" when those machine marks get flattened out during break-in. In some cases, the machine marks are deeper and will peen more before the gun settles down. The more endshake you start with, the faster the revolver will "age". Any fore and aft cylinder movement will result in a "jackhammer effect" and the wider endshake gets, the more momentum the cylinder develops, which accelerates endshake peening even more. After a cylinder develops .005" of endshake, it can easily accelerate to dangerous proportions with just a few hundred rounds of 357 Mags.

Here's what happens inside the revolver: When a cartridge is fired, the cylinder immediately thrusts to the rear until it is stopped by the ratchet column striking the recoil shield. As soon as the bullet starts to exit the case and enters the cylinder throat, the friction of the bullet moving forward in the throat thrusts the cylinder forward. When the bullet exits the cylinder throat and passes the B/C gap, the cylinder is again thrust to the rear. The forward thrust is the most violent because that's where peak pressure occurs. Consequently, that's the position where the crane tube face contacts the inner mating surface in the cylinder's center hole so that's also where the most peening takes place. Any time you have tight cylinder throats or use oversized bullets, way more pressure will build as the bullet is trying to pass through the throat. This will accelerate endshake much faster .... in fact with the several thousand revolvers I have worked on, every time without fail ... when you see tight cylinder throats, you will also see excessive endshake. The absolute worst case for endshake is shooting hot loads with oversized bullets (or undersized throats).

KaTo, Good points! Your SP-101 may have been shipped with a couple thousandths endshake then added a couple more as it broke in. This could result in marginal endshake right off the bat. Hard to say ... but the fact is, your SP-101 needs some attention (endshake bearings) before the ratchet column and the recoil shield get peened beyond repair.

I'm curious .... why do you think the 4.2" SP-101 won't work with your Crimson Trace laser grips? Is the grip stud different on the 4.2"??? I really doubt that but I haven't had one apart yet. AFAIK, all SP-101s share exactly the same grip stud.
 

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Well this really sucks. I need to check my GP-100 then. I only fired .38's my very first box and since it has been Magnums. I bought it and the Redhawk to shoot Magnums and if they can't without being trashed maybe time to sell my Revolvers and move to all Semi's.
 

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Discussion Starter · #11 · (Edited)
I saw in another posting that crimson trace had listed on their website "Fits Ruger SP101 [manufactured prior to 2010]." under the fit notes for both models of sp101 laser grips, the LG-303 and LG-111. I suspect that it just means they tried the grips on a 2010 model and listed it as such in a somewhat confusing manner on their website. I would suspect there would be an outcry if anything where to change on the sp101. According to the old mantra, if it aint broke, dont fix it.

I think after the amount of amazingly reliable firepower I've put through this ol ruger, it has earned a bit of attention.
 

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intercooler, There's not a gun made that will last forever. Why do you think gunsmiths stay so busy? GP-100s, Redhawks, and Super Redhawks are the strongest DA revolvers on the market and will last a long time. Yes, you will have to do some maintenance down the road but not nearly as much as any semi-auto. Do you ever have to make repairs on your car? Really not that much difference ... any mechanical device will wear out with use ... it's a fact of life. The harder you push the limits, the faster things wear out. With any gun, the hotter the loads, the faster they wear.
 

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Springs and stuff in the Semi's. It sounds like the revolver needs some major hard parts replaced.
 

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intercooler, It's not as bad as you think. Most "overhauls" on Ruger DAs involve replacing the cylinder latch and pawl, plus installing endshake bearings. Maybe $30 worth of parts and an hour labor. With semi-autos, barrels and sometimes slides give out ... plus recoil springs every couple thousand rounds. Same concept though ... hot loads take their toll no matter what gun you use. If you don't inspect your guns for known wear areas like KaTo did, any revolver or pistol can turn to crap.
 

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What checks and inspections should I be doing on my GP-100? Is their a how-to with specs and procedures here somewhere?
 

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intercooler, Endshake is to revolvers what tread is to tires. When endshake starts approaching .005", it's time to take action before the frame and cylinder get damaged. Other known problem areas for all revolvers is the cylinder lock notches. If you pull the trigger too fast in DA or cock the hammer too fast in SA, the lock notches and cylinder latch will take a beating and eventually peen where the cylinder has too much side play. Another thing to check is "carry up" timing. This is done by slowly pulling the trigger in the DA mode. The cylinder should lock up before the hammer drops. This is a good wear indicator for the ratchets, pawl (hand), and hammer dog. No amount of lubrication will prevent peening, which is the mechanical action where two parts strike each other versus friction when two parts rub against each other.
 

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Well this really sucks. I need to check my GP-100 then.
It's pretty expensive shooting a GP100 to the point of failure, most don't have the time, or the cost of the ammo.

I have a BH .357 with an easy 10K rounds through it, mostly cast loads at medium levels. It has no measurable wear on anything. But I was able to stress a nice M19 shooting thrill level loads with heavy bullets and lots of W296, took about 5 years at maybe 100-150 rds a month. Even then it was serviceable as a shooter, just loose. My K-38 saw far more action, a lot more, and was good as new when I sold it to a K-38 fan. Bad decision.

My question for KaTo was pure curiosity, as I will not shoot any max loads from my SP101, ever. It will get some jacketed stuff, moderate loads, but mostly cast/extruded lead also at moderate levels by .357 standards. If I really need power in a handgun, I'll bring my SBH to the game. I'm thinking if it will take 2K factory 158's, it will easily digest all of the stuff I feed it, and still be working when I leave for the next world. Taxed to death by Democrats.
 

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Discussion Starter · #18 · (Edited)
If you do the math I have actually put over twice the cost of ammo through this gun than its original purchase price. Back when ammo was cheaper to boot. Not typical use by any means. I actually have moved to lead 38's primarily and with all the loose brass floating around have a nice stockpile for loading. I have since picked up a new sp101 with a b/c gap running between 0.007 max and 0.004 min factory fresh. I re-took the measurements of mine after getting all of the lead off and it is actually at 0.008 max and 0.002 min, quite a difference between the two. The difference in the wear items, pawl, transfer bar, and yoke, is also very noticeable and the triggers are like night and day. I called ruger and they say that since my hammer is fully functional and not related to the wear that they will take care of it, shipping and all. Go Ruger!

For educational purpose I took a picture of the end of the yoke tube on the new and old sp101, I'll let you figure out which has 2k on it.

I did notice that the carry up timing of my new sp101 is solid for four cylinders and quite a bit slower on on, still reaching full lock up as the hammer drops. I know that pawls are available as it is not a "factory fitted part" and I am wondering if they are also available as oversize? I can find over sized pawls for the single action while DA seems to have none.
 

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Endshake is fore and aft cylinder movement when the cylinder is locked into the frame. The way to measure it is to use an automotive type gap gauge (feeler gauge) and measure the barrel-to-cylinder gap (B/C gap) by first wedging the cylinder fully forward. Measure the B/C gap again with the cylinder wedged fully to the rear. Endshake will be the difference between the two measurements. For a SP-101, you want about .002" but not more than .005". If endshake is too tight, the cylinder will bind up. If it is excessive, several conditions could result including misfires from light primer hits, cylinder unlatching when fired (very dangerous), cylinder dragging on the barrel, etc.

Endshake comes from four sources ... the end of the crane tube (S&W calls it a yoke tube) will peen and get shorter. A channel will get cut inside the cylinder's center hole, which is the mating surface for the crane tube. This causes the crane tube to seat deeper. The other two areas are the end of the ratchet column and the recoil shield where the ratchet column mates. Generally, all four surfaces will peen and increase endshake. Short of replacing the frame and/or cylinder, there's nothing you can do about excessive endshake if if comes from the recoil shield or the ratchet column.

How can you determine the source of the problem? If the cylinder moves too far rearward where the B/C gap exceeds .008" (.004"~.008 is normal, .006" is optimum), either the ratchet column has peened shorter or there is a depression in the recoil shield. You can usually see or feel a depression in the recoil shield. If the ratchet column is peened, the normally sharp edges will show evidence when compared to a new gun.

Based on the measurements posted by KaTo, it appears the B/C gap is wider than normal, which indicates a couple thousandths peening at the rear ... ratchet column, recoil shield, or both. The only fix is to replace the cylinder and/or frame but because the B/C gap is still in spec (barely) repair would not be necessary.

The worst issue is when the B/C gap is way too tight with the cylinder pushed forward ... almost causing the cylinder to scrape on the barrel. This can be repaired by installing "endshake bearings", which are nothing more than very thin washers. Before installing endshake bearings, two very important issues must be resolved. The first requires a "facing cutter" tool that removes a few thousandths from the end of the crane tube, removes the peened area, and squares up the end of the tube so it will mate properly with the bearing surface inside the cylinder's center hole. The inner hole mating surface must be dressed smooth and straight to eliminate the channel that was cut by the crane tube. The tool used to do this is a cylinder shaped grinder bit. I buy the ones with a 1/4" shaft and a 1/2" abrasive cylinder then use a shaping stone to size the diameter so it will just fit in the gun's cylinder center hole. After shaping the outside diameter, I use epoxy on the circumference of the body of the grinder bit so it won't damage or enlarge the diameter of the cylinder's center hole. This leaves a flat abrasive tip on the grinder bit so you can chuck the bit in a variable speed drill and hone the inside mating surface, typically removing about .005".

With the crane tube cut shorter and the inside cylinder hole deeper, it will increase endshake by several thousandths. No problem ... just stack endshake bearings until endshake measurements are within spec ... closer to .002" is best. Brownell's sells endshake bearings (made by Power Custom) in .002" thickness ... pack of 10 for about $20.

After endshake bearing are installed properly and endshake is well in spec, the gun will actually hold up better than when brand new. As noted above ... 357 Mag ammo takes its toll so it's much wiser to shoot 38 Specials for practice and run a cylinder or two of Mags now and then just for grins. If endshake is allowed to get out of control (more than .005"), it will allow enough fore and aft motion to "jackhammer" endshake much faster. At some point, the cylinder latch will release when fired and could result in a dangerous situation.
Would this also apply to the GP100?
 

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KaTo, Based on the shape of the left crane tube, I would highly recommend sending your SP-101 back to Ruger or putting it in retirement status. That nasty angle on the end of the crane tube has no doubt cut a deep channel in the cylinder's center hole. By the time you get the crane tube dressed back and the channel in the cylinder taken care of, the crane tube is going to be too short for endshake bearings. Most likely, Ruger will replace the cylinder and crane, which should restore the gun back to good operating condition.

harrydog, Ruger doesn't share their specifications with the public so the numbers I quoted were general specifications that apply to most all DA revolvers, no matter what brand. GP-100s have a stronger crane tube than a SP-101 but if enough magnum ammo has been fired, it will eventually peen just like Kato's SP-101. The same goes for Securty-Sixes, Redhawks, and Super Redhawks. S&W revolvers have a much thinner yoke (AKA crane) tube so they will suffer from endshake far sooner than any Ruger. That said, a standard K-frame 38 Special S&W will last 30,000~40,000 rounds before endshake become an issue. The same basic K-frame 357 Mag firing 357 Mag ammo probably won't last more than a couple thousand rounds before it needs endshake bearings.

When people buy the large frame S&Ws and Rugers ... specifically a S&W Mod 27 or 28, or a Ruger 357 Mag Redhawk, they think they are getting the strongest guns money can buy because the cylinders are so thick. These revolvers were designed for 44 cal but chambered for much smaller 357 Mag cartridges, which makes the cylinders very heavy. When endshake allows a little fore/aft movement, these heavy cylinders develop a lot of momentum, act like a battering ram, and beat the yoke/crane tube to death. Further, the massive cylinders also beat the lock notches to death when the revolvers are operated in a normal manner. A combination of peened lock notches and excessive endshake is an accident waiting to happen. Likely, this is the reason why Ruger quit making the Redhawk in 357 Mag.

Here's why excessive endshake is so important .... If you look at the top area of a cylinder latch and the lock notches in the cylinder, you will note they are crescent shaped. When a revolver is well within spec, the crescent cylinder latch locks into the cylinder's crescent lock notches and holds the cylinder horizontally where the chambers align with the bore. The only thing that holds the cylinder latch in position is a little coil spring. When endshake is normal, the cylinder can't move forward far enough to dislodge the latch; however, when the cylinder develops enough forward endshake movement due to peening like Kato's left photo, the rounded cylinder latch will cam down when the revolver is fired and release the cylinder. This can be a very dangerous condition because the bullet exiting the cylinder throats could strike the side of the barrel instead of being directed into the forcing cone. Besides totally ruining the gun, it could also present a serious danger to the shooter.
 
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