Does a cylinder wear FORWARD, toward the forcing cone?

[C5rider]

Was looking at my New Model Blackhawk 45 Colt and the cylinder gap is inperceivable, even if you hold it up to the light. There is evidence of the cylinder touching the forcing cone as it rotates. The witness marks run in the direction of cylinder rotation.

I have cleaned the forcing cone and the front of the cylinder so, that's not it. I've heard how stout these guns are and, even so, wondered why the cylinder would wear forward instead of on the back surfaces since the force would be pushing backwards while firing?

 

[osteodoc08]

Is this a brand new gun or one with some use? All mine have a perceivable gap and I have no discernible wear even after thousands of rounds on my Blackhawks. My Smith 57, 686, 586 are all still pretty tight. So to answer your question, I just don't know about forward wear. I know I can see the outlines of the rim on my guns from the brass. Other than that, ???

 

[Steve C]

You may have thought you cleaned the forcing cone but the face of the forcing cone will accumulate lead fouling deposited from lead vaporized from the bullets base when fired. Eventually this closes the cylinder/barrel gap. Because of the way the lead is deposited its indistinguishable from the metal of the forcing cone. The cure is to re-gap the revolver by removing these deposits with a tool designed to do this and leave the end square. I have also seen an experienced smith re-gap a revolver using a flat file but wouldn't recommend it for the amateur.

 

[Longhorn 76]

Yes, the gap will decrease with time.

 

[Certaindeaf]

If I touches, it touches. That's generally not good at all. I'd be half concerned.

 

[1911Tuner]

Back in the day when revolvers were fired exclusively with lead bullets, barrel to cylinder gaps had to be generous enough to accommodate lead accumulation without rendering the gun non-functional. Generally, .005-.007 inch is/was enough for lead bullets, assuming that the shooter keep the revolver relatively clean.

Enter the jacketed bullets of more recent times, and the gaps can be tightened up quite a bit without causing a problem...but they still require cleaning due to carbon build-up. It's just not as critical as it is with lead bullets.

Bill Ruger's revolvers were/are designed and built primarily for use with jacketed bullets, which is why the tiny B/C gaps are noted in Ruger revolvers...most notably Blackhawks and Super Blackhawks...which have been seen as tight as .002 inch in some examples. Those don't do well with cast or swaged lead bullets without frequent cleaning around the forcing cone/cylinder face area.

 

[The Lone Haranguer]

The cylinder can develop end play (commonly known as "end shake"). Without rotating the cylinder, try, with the hammer both cocked and uncocked, and with a light source, to move it back and forth. It should not have any significant amount, perhaps .002 or .003" maximum. If you see the cylinder gap visibly changing this end shake is excessive. The cylinder can also shift forward in the window, which would cause the gap between the rear of the cylinder and the frame to grow wider. Whichever is happening, if there are literally drag marks on the cylinder face from contact, and it isn't a fouling or carbon buildup, the revolver needs to be repaired. Despite not having a written warranty, Ruger will stand behind their product.

 

[Certaindeaf]

Well that's all well and good but what if it touches?

 

[dfariswheel]

What causes end shake is battering of the cylinder and frame from either lots of use, or from shooting very hot loads.

What happens is the cylinder must have at least a tiny amount of movement to allow fitting it into the frame.
As the gun is used, especially with hotter loads, the movement of the cylinder back and forth acts as an impact hammer and it compresses the cylinder bushing, and can cause impact battering the face of the frame.

If it gets bad enough the cylinder can actually start to contact the rear of the barrel.
That's BAD. That quickly starts damaging the front of the cylinder and the rear of the barrel.

In a single action the correct repair is to have a new cylinder base pin bushing installed.
Ruger uses a pressed-in cylinder bushing which is a factory job.
Ruger can repair it for a reasonable charge.

The only other option is to install a thin washer on the cylinder base pin between the front of cylinder and the frame.
With that, you have to find a super thin washer of the right size, and each time you remove the cylinder you have to be very careful not to loose it.

My advice is to return the gun to Ruger. If the gun has been fired with hot loads, there's a chance the frame could have been impact damaged too.

 

[Certaindeaf]

What causes end shake is battering of the cylinder and frame from either lots of use, or from shooting very hot loads.

What happens is the cylinder must have at least a tiny amount of movement to allow fitting it into the frame.
As the gun is used, especially with hotter loads, the movement of the cylinder back and forth acts as an impact hammer and it compresses the cylinder bushing, and can cause impact battering the face of the frame.

If it gets bad enough the cylinder can actually start to contact the rear of the barrel.
That's BAD. That quickly starts damaging the front of the cylinder and the rear of the barrel.

In a single action the correct repair is to have a new cylinder base pin bushing installed.
Ruger uses a pressed-in cylinder bushing which is a factory job.
Ruger can repair it for a reasonable charge.

The only other option is to install a thin washer on the cylinder base pin between the front of cylinder and the frame.
With that, you have to find a super thin washer of the right size, and each time you remove the cylinder you have to be very careful not to loose it.

My advice is to return the gun to Ruger. If the gun has been fired with hot loads, there's a chance the frame could have been impact damaged too.

Well that's intuitive and all like that. I think the gentleman said he has a binding issue though.

 

[rcmodel]

wondered why the cylinder would wear forward instead of on the back surfaces since the force would be pushing backwards while firing?

It isn't pushing backwards.

When a round fires, the case slips back in the chamber until it slams into the recoil shield.

And recoil starts the moment the bullet starts moving forward at the same time.

At that point, the gun recoils to the rear violently.

And tries to leave the heavy cylinder and remaining ammo setting in the place where the gun kicked away from it. (inertia)

SO the cylinder is just setting there minding it's own business, when the frame flies backward, causing the gas ring to pound the front of the frame where it contacts it.

Then by the time it catches up, recoil is over and it's going backwards faster then the gun is until it slams into the rear of the frame.

Do it enough, and end-shake develops.

rc

 

[C5rider]

All good information gentlemen. In fact, there was a binding when trying to cock the hammer. When it would reach around the point where a 3-screw would have the first click as the hammer is pulled back, it would catch. Then, if you released the hammer and tried it again, it would rotate freely and cock fully. Didn't seem to be any particular bore in the cylinder that would do it and, it didn't do it every time.

I'm thinking that the ol' girl may have earned her a trip back to Ruger. Thinking of asking them about a 45acp cylinder for it as well. It's a 7 1/2" bbl NM Blackhawk. It looks in good shape, just has a few issues. I don't know the history of the gun before I got it. Only that the previous owner traded this, a three-screw single-six and a .41 Magnum Ruger for a Desert Eagle because he felt he needed more to go "hog huntin".

I'll try and get some pictures of it.

Hadn't thought of it that way RC. As always, great information! Thanks for helping me understand the dynamics at play.

 

[Jim K]

There are two erroneous ideas here. The first is that the barrel-cylinder gap should be minimal, almost invisible to reduce or eliminate gas loss and increase velocity. The second is that if a revolver cylinder binds it is always the result of carbon buildup; this idea appears confirmed when a binding cylinder operates normally after the buildup is removed.

The real problem is that if the b-c gap is too small (under about .004"), the cylinder will expand lengthwise from the heat of firing enough to bind. How many shots does it take? Sometimes as few as 2-3 shots, sometimes two cylinders. Carbon buildup can contribute to the problem but is not the real cause. Of course when the shooter stops firing to clean the carbon, the cylinder cools down and returns to its normal dimensions until firing heats it up again.

So, no matter what the ammo used, or the condition of bushing, the b-c gap HAS to be large enough to deal with heat expansion. I recommend a gap of .006-.007" as close to ideal for reliable functioning.

Jim

 

[rcmodel]

I recommend a gap of .006-.007" as close to ideal for reliable functioning.

+1 on that.

Cylinder faces are self-cleaning when using smokeless powder loads.

Anything thick enough to bind up a cylinder is blown off every shot.

The thin film of leading or carbon you see when you clean the gun is not thick enough to bind up the cylinder.

If it was thick enough, hot powder gas would blow it off every shot.
Like flame cutting top straps!!

Heat expansion on the other hand??
Well, it doesn't go away until the gun cools off, and you are home cleaning it and think you fixed the problem..

rc

 

[unspellable]

I've always been a bit dubious about the cylinder expansion due to heating theory. Some revolvers have a nominal cylinder gap of 0.003 inch, including four in my collection and I have never experienced cylinder binding.

 

[unspellable]

End shake

PS. If the cylinder expands all that much the end shake would disappear. Correct end shake is only in the range of 0.001 to 0.003, less than the cylinder gap. The cylinder should bind due to heating by loss of end shake before loss of cylinder gap.

 

[BCRider]

OK, silly little moment here..... C5, when you look at the gap are you pulling the cylinder back towards the recoil shield? I ask only because the hand spring tends to push my cylinders forward a little. So to examine the gap I need to pull the cylinder back to take up this play. The result being that the end float of the cylinder is the same amount as the width of the B-C gap. And if I simply LOOK at the gap without pulling the cylinder back like this they all look like they have minimal to zero gap.

 

[murf]

make sure your base pin has not backed out.

murf

 

[winfried]

A)
0.004 = 0.1016mm: Steel expands 0.0102mm/degC/m so; if I have not calculated wrong, a 50mm cylinder must get to a temperatur of 199 Celsius to produce such expansion. At about 185 Cels you get a cook-off!

3 shots can never expand a cylinder noticeable.

B) At the gap is the pressure peak. It is hardly possible to get noticeable carbon or lead build up to withstand this pressure. Proof is that on some frames just above the gap a groove is visible caused by gas cutting.

C) If there would be carbon or lead build up on the forcing cone, the same would be visible on the cylinder as well. Silver grey lead streaks are observed on the cylinder, but in such a thin layer that it is not measureble.

D) Recoil velocity is not as vicious as generally assumed. For instance a 1000g gun firing a 10g bullet with Vo 400m/s the recoil velocity as a result of the moving bullet is only 4m/s or about twice the speed of a fast walk.
In addition to this there is the rocket effect of the gas exit which can add another 50% more recoil.
Easy to understand in the metric ballistics, cumbersome in the antiquated imperial system.
All this applies to strong loads, I am not sure what happens when you shoot weak loads with too slow/too little powder.

I suggest, first of all, mark your cylinder with tippex to find out if only one or which and how many chambers have the problem. With hammer down, measure forward/rearward endplay. That takes guesswork out of the problem.

It is also not clear if there were shells or cartridges in the cylinder when the binding occured. If there is a binding, forcing the hammer back will damage the timing.

Regards

Winfried

 

[BSA1]

Another thing to remember when checking the b/c gap is to check it from both sides of the gun. I had a Ruger that measured .003" from one side and .001" from the other. I think gun rag writers are largely responsible for the tight b/c tolerances. Since the b/c gap is easy to measure with spark plug gauge and gun rag writers are also in need to spice up their article well then tighter means closer attention to quality right? The problem is shooting ammunition is dirty and varies according to powder and bullet.

I also share the opinion of .006 -.007" gap although I gap my Single Actions at .008" as I shoot black powder.

 

[C5rider]

Thanks for the interest and information so far. I hope I can help clarify a little more about the gun and what is going on.

Here are some shots of the cylinder and the forcing cone/barrel. If you look closely, you can see where the two have been rubbing each other. Correct me if I'm wrong, but these two shouldn't be able to come in contact with each other, correct?

I understand the concept of the cylinder moving around a little since it needs some room to operate and, it would be very hard to install/remove if it were a tight machined (interference) fit.

I am of the opinion that the center raised area in the middle of the cylinder is worn, allowing the two to come in contact. I was of the understanding that Ruger doesn't install bushings, but instead, this is a machined part of the cylinder?

If you look closely at the photo of the forcing cone, you can see the lines making an arc from left/right where the cylinder was running into the back of the barrel. To me, this is entirely too close. I understand that fouling may contact the barrel if set too tight, but the cylinder marks (to me) confirm that the two metal parts are touching, not carbon/fouling/etc.

Oh, and I also included a photo of the gun, just for the beauty shots.

Anyone have an idea what grips these are? I was really hoping it had the originals but these are starting to grow on me and I'm sure that they will come in "handy" if/when I decide to put some stout loads through the ol' girl.

Me thinks this might be a Ruger fix. And, might be a good time to look into that ACP cylinder as well.

Thoughts?

 

[C5rider]

I did a little more investigating on the gun and measured the cylinder gap.

With the cylinder all the way back against the recoil shield with no cartridges in the cylinder, I can get a .003" feeler gauge between the cylinder and forcing cone. A .004" gauge will not go. That seems tight, and if it was an issue of excessive wear, wouldn't it be more?

I'm relatively new to in-depth revolvers so please bear with me. But does it seem that the "worn" part would either be the forward bearing/bushing part of the cylinder (allowing the decrease in B/C clearance or, the front part of the frame where the base pin fits into and the cylinder bearing/bushing meets?

I know that Ruger had put the ending serial numbers on the convertible models, but did they do that on the single-cylinder version as well? Could someone have possibly swapped out the cylinder on this gun?

Please understand, I'm not trying to be ignorant, or not-listening to anyone's advice, just trying to understand a little more about my gun and what is going on. I know that a trip to Ruger is most-likely in the works, I'm just trying to understand the situation, rather than simply handing it over to them and saying, "Broke!"

I know, I'm funny that way. Thanks for putting up with me.

 

[Old Fuff]

Push the cylinder fully forward and hold it there while you check the gap with your feeler gauge. Repeat and check each chamber.

If, when the cylinder is held fully to the rear, the gap is only .003" it's way too tight - especially if you shoot lead bullets. If the cylinder face got leaded I'd expect it to bind.

The part at the front of the cylinder that the cylinder pin goes through is called the "hub." In production Ruger assemblers have cylinders with slightly diffenent hub lengths. They go with whichever one has the least end shake (back and forth movement as opposed to rotational movement), and then check the cylinder/barrel gap to see if it's in spec. Individual hand fitting would take too much time.

 

[C5rider]

Thanks Fuff!

The thinnest gauge I have is .002" and when I push the cylinder forward, the gauge will not go between the cylinder and the forcing cone. As soon as I release the forward pressure and allow the cylinder to come back a hair, then the gauge goes right through. I checked every cylinder from both the left and the right side of the barrel and it will not go with the cylinder pushed forward.

It seemed awful tight to me, even with the cylinder all the way back against the recoil shield (.003"). That's what led me to wonder if the cylinder might have been swapped out at some point. But, I'm not sure.

Ruger's site shows that the gun was manufactured in 1993, so I would be suspect if this gun went through it's life so far with such a tiny B/C gap. But again, I can't say for sure. I bought it used.

Ruger wouldn't turn out a gun with that tight of tolerances, would they?

Yes, I do shoot lead bullets. I don't push them hard, but I do shoot them for target practice.

 

[MartinS]

Not the original cylinder.