Ruger Forum

Endshake....101

This is a discussion on Endshake....101 within the Ruger Double Action forums, part of the Pistol & Revolver Forum category; It is my understanding that .002 of endshake is acceptable/needed in a GP100? My SP101, in full lock up(cocked, hammer down, trigger held) has just ...


Go Back   Ruger Forum > Pistol & Revolver Forum > Ruger Double Action

Reply
 
LinkBack Thread Tools Display Modes

Old July 28th, 2012, 06:00 AM   #1
 
Join Date: Jul 2012
Location: Lakeland, Mn
Posts: 51
ScottMn is on a distinguished road
Endshake....101

It is my understanding that .002 of endshake is acceptable/needed in a GP100? My SP101, in full lock up(cocked, hammer down, trigger held) has just a small amount. It's very close to .002(slightly less). Is this acceptable?


Thanks.....



ScottMn is offline  
Advertisements
Old July 28th, 2012, 06:34 AM   #2
 
Join Date: Jun 2012
Location: USA
Posts: 147
Colt Seavers is on a distinguished road
Yes, it is acceptable. The only real problem you might have is being that close to the forcing cone might cause you to have to clean the cylinder face and forcing cone more often to prevent friction drag from fouling buildup.

If memory serves, most company's standard is .002~.008 is acceptable.


Edit: I'm assuming you mean barrel to cylinder gap.

Last edited by Colt Seavers; July 28th, 2012 at 06:41 AM.
Colt Seavers is offline  
Old July 28th, 2012, 06:36 AM   #3
 
Join Date: Nov 2008
Location: Arizona Wilderness
Posts: 336
Snobal is on a distinguished road
I'm no expert but it sounds good to me.

The endshake on both of my SP101's is .003".

B/C gaps are .006" and .004".

The one with the .006" B/C gap is a 3" and is my favorite, all-round, "do everything" .357 Mag revolver. Just for fun, I've shot several Bullseye Matches with that 3" gun and wadcutter bullets.

What is the barrel/cylinder (b/c) gap on your SP101?

I get good velocity (by my chrono) and reliable functioning with B/C gaps in the range of .004" to .007".
Snobal is offline  
Old July 28th, 2012, 07:46 AM   #4
 
Join Date: Mar 2012
Location: Idaho
Posts: 787
Seneca is on a distinguished road
End shake is excessive forward/back movement of the cylinder, there needs to be a certain amount of forward/back movement for the revolver to operate properly and not bind.

It's when that forward backward play becomes excessive that you have a end shake or a timing/headspace issue.

I can live with .004-007 thousand barrel cylinder gap with a couple of thousandths play. It's a .015 to.020 plus barrel cylinder gap, light firing pin strikes and the cylinder not locking into battery that I would consider problematic.

Unless you have the proper tools and knowledge to correct endshake it's best to have a competent gunsmith do it or return the revolver to the factory for service.

The good news is you'll shoot a new GP100 or SP101 for a very long time before endshake becomes an issue.
Seneca is offline  
Old July 28th, 2012, 10:22 AM   #5
Retired Gunsmith
 
Iowegan's Avatar
 
Join Date: Aug 2006
Location: Blair, NE
Posts: 8,811
Iowegan has a spectacular aura aboutIowegan has a spectacular aura about

Awards Showcase

Endshake and B/C gap are two totally different animals, but they are related. As Seneca stated, endshake is the fore/aft movement of the cylinder. B/C gap is the distance from the cylinder face to the rear of the barrel when the cylinder is held to the rear (measrued with an automotive type "gap gauge"). If endshake becomes excessive, bad things can happen ... such as misfires from excessive headspace, dramatic loss of velocity, excessive "gap spitting", accelerated top strap flame cutting, or worse yet ... in extreme cases the cylinder can jump out of lockup and result in a very dangerous situation.

Here's what happens when a round is fired: the outside surface of the bullet contacts the cylinder's throat and pushes the cylinder forward until it stops when the face of the internal crane tube contacts the bearing surface inside the cylinder's center hole. When the base of the bullet crosses the B/C gap, chamber pressure thrusts the cylinder to the rear until the ratchet column strikes the recoil shield. This "jack hammer" effect will eventually cause endshake to increase. Once endshake exceeds .005" the cylinder will develop more momentum as it moves fore/aft and the jack hammer effect will accelerate wear even more.

B/C gap specs for nearly all revolvers is .006" +or- .002" (.004~.008"). Endshake always increases the B/C gap at the most critical point in bullet travel ... when the base of the bullet is flush with the rear of the barrel's forcing cone. This will cause more pressure loss, lower muzzle velocity, more "gap spitting", and more top strap flame cutting. Endshake specs depend on the brand and model .... S&W revolvers are way more sensitive to endshake so their specs are tighter ..... typically from zero to .003". Ruger DAs have a more massive crane tube so they aren't as prone to wear. As noted above, a Ruger DA revolver should have no less than .002" of endshake and no more than .005". When a new revolver leaves the factory within these specs, chances are it will last for many many thousands of rounds.

There are four areas of "wear" that affect endshake .... the end of the yoke tube will peen, making it slightly shorter, the bearing surface inside the cylinder's center hole will develop a "channel" which allows the yoke tube to seat too deep, the ratchet column will peen and make it shorter, or the recoil shield will develop a divot that allows the cylinder to move back too far. Generally, in a well used DA revolver, all four of the wear areas will be affected and add to the total endshake. The way you measure endshake is to wedge the cylinder to the rear and measure the B/C gap. Next you wedge the cylinder to the front and measure the B/C gap again. The difference in the two measurements will be total endshake. In a Ruger DA revolver, if endshake is too tight (under .002") the cylinder will bind, causing DA trigger pull to be harsh. After a box or two of ammo has been fired, endshake will usually open up a few thousandths and make the cylinder rotate easier. S&Ws work different ... their max endshake is only .001" different than a Ruger's minimum, so ... don't try to apply one gun's specs to a different brand.

Repairing endshake: First you have to do some trouble shooting to find out where the problem(s) may be. If the cylinder moves too far forward where the B/C gap is less than .004", it's either a peened yoke tube face or a channel cut inside the cylinder's center hole bearing surface ... maybe both. This condition is repairable. Next is to measure headspace. This is done by inserting a "virgin" case into a chamber and aligning the chamber with the firing pin hole. Again, use a gap gauge to measure the minimum and maximum distance between the case head and recoil shield by holding the cylinder to the front and again by holding the cylinder to the rear. A typical DA revolver will have a headspace of .008" +or- .002". If headspace is under .006", it means the ratchet column has worn or the recoil shield has a divot .. or both.

There's virtually nothing you can do to repair a frame when a divot develops in the recoil shield ... short of replacing the frame. Likewise with the ratchet column on the cylinder ... short of replacing the cylinder, there's no fix. Shims between the ratchet column and the frame (recoil shield) won't work because the hand that rotates the cylinder won't be able to advance the ratchets. Fortunately, these two conditions seldom are the sole source of excessive endshake.

When the yoke tube wears or a channel is cut inside the center hole bearing surface (the most common cause), there is a way to repair the gun. First you must use a rotary grinder bit to "dress" the inside bearing surface and remove the channel. After the channel in the bearing surface has been removed, it's just a matter of installing endshake bearings, which are nothing more than very thin washers (.002" thick). Endshake bearings can be stacked to bring endshake back into spec. Installing endshake bearings without removing the channel usually doesn't work ... the first time you fire the gun, the thin washers will form into the channel and bind up cylinder rotation. Likewise, if you use endshake bearings to compensate for ratchet column or recoil shield wear, you will end up with a headspace that is too tight. A slightly thicker case rim or a slightly "proud" primer will bind up cylinder rotation.

Preventing endshake: There are two primary causes of endshake wear .... shooting hot loads and shooting bullets that are oversized. As an example .... 10,000 rounds of 38 Specials will cause less endshake wear than just 500 rounds of 357 Mags. So .... shoot 38 Specials for practice and shoot 357 Magnums sparingly. Check your cylinder throats ... if they are too tight to allow a bullet to pass through with just finger pressure, the throats are too tight or your bullets are too fat. As noted above, the cylinder slams forward when the circumference of the bullet contacts the throat. If the bullet is larger than the throat, it causes the cylinder to be forced forward much harder than with a properly sized bullet. In the thousands of revolvers I have worked on in my gunsmithing career ... I've found without exception ... tight cylinder throats or oversized bullets always result in excessive endshake wear. There's absolutely no advantage with shooting bullets that are larger than the throats because they will get sized down as they pass through.
Iowegan is offline  
Old July 28th, 2012, 02:14 PM   #6
 
Join Date: Jul 2012
Location: Lakeland, Mn
Posts: 51
ScottMn is on a distinguished road
Thanks for the responses. I realise that this question has probably been asked many times and your time is much appreciated.

I went out to the shop and this time cut myself a walmut wedge and under full lock up measured again just to settle my mind. Fully forward I measured the B/C gap at .004 and wedged back at .006. Headspace I left alone for the moment. I have plenty of used brass but no unloaded/unprimed cases. I could use one of the spent rounds but I'm not sure if it would tell me anything.

What is the standard rim dimension for .357/38 brass? I would think you would be able to get an accurate measurement of headspace knowing that dimension and stacking a few gauges?

Iowegan, I look forward to being able to read your tutorial for a trigger tune on the SP101. Many have commented on how well they liked the results. I have been using Break Free as a lubrication but the other night I blew out and cleaned the action and then lubricated with a product called Gun Butter that I use on my semi-autos. It has worked well on them and it didn't disappoint me in the SP. Noticeable difference but there's nothing that can substitute for a little honing and polishing in the right places.


Take care,

Scott


PS. I should add that I did notice when checking the B/C gap that it was slightly tighter on one side of the cone than the other. Not sure if this is important or not but I thought I would mention it.

Last edited by ScottMn; July 28th, 2012 at 02:17 PM.
ScottMn is offline  
Old July 28th, 2012, 03:55 PM   #7
Retired Gunsmith
 
Iowegan's Avatar
 
Join Date: Aug 2006
Location: Blair, NE
Posts: 8,811
Iowegan has a spectacular aura aboutIowegan has a spectacular aura about

Awards Showcase

ScottMn, If you could find a "perfect" revolver, the B/C gap would be identical from all angles and perfect for each chamber alignment. In reality, this rarely happens in mass produced revolvers of any brand. Seems most cylinders have a couple thousandths runout where one chamber position might have a bit tighter or looser B/C gap than the others and barrels are seldom squared off perfectly. Add to this the variations in ammunition and you will soon see why there is a need for a B/C gap and a headspace gap.

The 38 Special case specification for rim thickness is .058", whereas a 357 Mag is .060" .... so there is already a difference that will affect measurements. Most brass actually has a thinner rim than spec ... .055" is normal for 357 Mags. Each time a case is fired and reloaded, the rim gets a tad thinner. So to get a text book reading, you need to sort through a pile of brass to find a case with a .060" rim. Is this really necessary? No ... as long as headspace is not excessive where it causes weak primer hits. Here's what happens when there is excessive headspace .... the cartridge has too much fore/aft free movement so when the firing pin strikes the primer, the whole cartridge is pushed forward. This absorbs a lot of the firing pin's energy so instead of a pronounced dent in the primer, you get a shallow dent that may not cause it to detonate properly. In other words, if your primers detonate reliably with a good solid dent, headspace is fine.

Your B/C gap measurements appear to be just right for endshake. When the gap is slightly tighter on one side, you can expect more gap flash on the other side. No big deal ... it has very minimal impact on accuracy unless it is grossly different.

Grease or oil in your SP-101 action? Not something I would recommend for a couple reasons. Oil won't stay on parts well ... it just drains off. Grease is way worse. With time, it will turn solid and will be counterproductive ... more friction instead of less. While "wet" it will draw powder residue, which is abrasive carbon. Turns out ... mating surfaces on parts will wear faster when wet than when totally dry. I run all my revolvers dry and only use a small dot of oil then wipe it dry with a clean patch. Guns are not car engines where you need constant lubrication. Your gun, your choice.
Iowegan is offline  
Old July 28th, 2012, 05:29 PM   #8
 
Join Date: Jul 2012
Location: Lakeland, Mn
Posts: 51
ScottMn is on a distinguished road
Iowegan, I hope that you aren't thinking that I'm after the "perfect" machine. I learned long ago that while it is possible to get close, the law of diminishing returns has a way of sneaking up on you....more money/time for the last 5% than for everything else combined.

This is more to make sure that I have a gun that is within spec(sure appears to be), establishing a base line for future reference, and probably most importantly...educating myself about the mechanics of a revolver. The other posters and yourself have been most helpful in that regard.

I understand your comments about oil/grease/lubrication on guns and triggers. Less is more. I'll clean it up properly when I break the gun down but the few drops I put on the pivot points I could reach made a differnce. A little work on it will surely improve it more than the gun butter.



Scott
ScottMn is offline  
Old July 29th, 2012, 11:42 AM   #9
Retired Gunsmith
 
Iowegan's Avatar
 
Join Date: Aug 2006
Location: Blair, NE
Posts: 8,811
Iowegan has a spectacular aura aboutIowegan has a spectacular aura about

Awards Showcase

ScottMn, No, I wasn't suggesting you were after a perfect specimen ... just trying to make a point.

Here's something to ponder .... Back when Ruger designed their very first DA revolver (Security-Six), they looked at the weaknesses of other brands ... namely the S&W mod 19 & 66 (primary competitor), and made sure their design was way stronger and more robust. S&W took a perfectly good K-frame design that held up exceptionally well in 38 Special and tried to turn it into a 357 Mag. The "Achilles Heal" of S&W K-frame 357 Mag revolvers is their skinny yoke tube and weak cylinder center hole bearing surface. Additionally, cylinder strength and frame strength is not suitable for 357 Mags and the rear barrel face is cut away to accommodate a swing-out cylinder. Cylinder lockup was also weak. At the time, S&W revolvers were 100% forged and machined ... no cast or MIM parts. This required all internal parts to be hand fitted, which is very labor intensive. Further, due the S&W's design, tolerances had to be held very tight or the revolver would not work properly. The good part about older S&Ws was ... they operated very smooth with a nice trigger pull, which was a product of hand fitted parts. Today's S&Ws use a lot of "drop-in" MIM parts and don't have the precision of the older guns. Their specs have "loosened", making them more like a Ruger, but not nearly as strong.

Ruger's result was nothing short of amazing in their K-frame sized Security-Six. The frame is cast and is way stronger in all respects. The rear of the barrel is not cut away and is more massive. The crane and crane tube (S&W calls it a yoke) is more massive, as is the cylinder itself. Ruger added a front cylinder latch, which made lockup way stronger. Nearly all internal parts in a Security-Six were cast and designed to work without being hand fitted. The good news ... Security-Sixes would hold up well to the old SAAMI 357 Mag pressure standards (46,000 CUP) whereas S&W Mod 19s and 66s would not. S&Ws had many strength problems so they petitioned SAAMI to reduce 357 Mag operating pressures to 35k psi. Even with reduced pressure ammo, the Mod 19 & 66 did not hold up well so S&W discontinued K-frame 357 Mags.

The only negatives about a Security-Six were its trigger pull and the full sized grip frame, which did not fit some shooters. An hour with common shop tools could turn a Security-Six into a very smooth action with an excellent trigger pull, leaving the full sized grip frame as its only negative. Ruger has never subscribed to a "fluff and buff" final finish on their parts, which adds a huge amount of labor cost, but leaves the action a bit raspy.

As time went on, Ruger went back to the drawing boards to design a revolver that would compete with S&W's popular L-frame Mod 586 & 686 ... a GP-100. They took the basic Security-Six design and manufacturing techniques then made some astounding changes. The full sized grip frame was eliminated and replaced with a "grip stud". This reduced the weight by a very significant amount so they used that weight advantage to beef up the frame and cylinder even more. Turns out, the L-frame sized GP-100 is nearly identical in weight to the older K-frame sized Security-Six but way more massive where it counts. It is also the same profile and is nearly identical in weight to a S&W 586/686. The GP-100 also has a vastly improved cylinder mounting system, "plug-in" front sights (adjustable sight models) and many other internal refinements. As with the Security-Six, hand fitting was eliminated for most internal parts. When the SP-101 was introduced, the design was nearly identical to a GP-100 ... except it was down sized to compete with S&W J-frame revolvers. Again, Ruger SP-101s have a major strength and longevity advantage over S&W J-frames and can be tuned to have far superior actions and trigger pulls.

What does this all mean???? GP-100s and SP-101s will operate perfectly well with magnum loads, last a very long time with minimal maintenance, yet do not need the precision found in older S&W revolvers. With a little bench time, action smoothness and trigger pull can rival any S&W.

Many people learned about the precision of older S&W revolvers and also learned if the specs were off just a tad, the gun wouldn't function properly. Trying to apply S&W specs to a Ruger revolver is a gross mistake. Rugers have much more forgiving specifications so if endshake, headspace, etc, are off a tad, the gun will still function safely, accurately, and last a long time. I think a lot of gun owners get strung out on "specifications". Yes, specs can be important but the real issue is ... does the gun function properly? In your case, it appears your revolver is well within spec and should last a long long time.

I'm not bashing S&W revolvers ... I own a bunch of the pre-MIM models ... just stating the facts so don't beat me up.
Iowegan is offline  
Old July 30th, 2012, 04:37 AM   #10
 
Join Date: May 2012
Location: USA
Posts: 2,178
ExArmy11b is on a distinguished road
Rugers tend to have looser specs in this regard, out of my many gp100s and six series guns, some came as new with nearly no end shake and others were a bit "sloppier". I have a like new .38 gp100 that needed an end shake bearing.... The gun was hardly fired and there's no way .38's loosened it that much.
ExArmy11b is offline  
Reply

  Ruger Forum > Pistol & Revolver Forum > Ruger Double Action



Search tags for this page
can excessive head space in smith and wesson revolvers, cause light primer strikes?
,

endshake

,

extreme s&w endshake

,

gp 100 endshake

,
gp100 cylinder wear
,

gp100 endshake

,

revolver endshake

,

ruger gp 100 endshake mormal

,

ruger gp100 endshake

,

ruger revolver endshake

,

ruger sp101 endshake

,
s&w k frame headspace
Click on a term to search for related topics.

Thread Tools
Display Modes


Similar Ruger Forum Discussions
Thread Thread Starter Forum Replies Last Post
SP101 Endshake Bearings Ridgeline Gunsmithing 0 August 6th, 2011 03:24 AM
Security Six cylinder endshake? demented Gunsmithing 5 June 16th, 2011 07:43 AM
sp101 endshake wrv Gunsmithing 3 October 22nd, 2009 03:40 PM
B/C gap = endshake G. Freeman Gunsmithing 1 September 29th, 2009 08:51 PM
Endshake Bearing? Longlosthiker Ruger Double Action 3 May 8th, 2009 09:50 AM

Top Gun Sites Top Sites List  
Powered by vBulletin 3.8.7
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.1
Copyright © 2006 - 2014 Ruger Forum. All rights reserved.
Ruger Forum is a Ruger Firearms enthusiast's forum, but it is in no way affiliated with, nor does it represent Sturm Ruger & Company Inc. of Southport, CT.